Re: [Elecraft] K3 SWR Anomaly

[N8LP]

This may be out of left field, but I seem to recall from the deep recesses of
my memory that there were some issues regarding an IF trap in the output of
the K3. It could be that one of the components in the trap has changed and
it now affects 40m. I don't know if newer K3s even have this circuit. Just
thinking out loud.

Larry N8LP





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[Elecraft] K3 swr anomoly

[Jim Douglas via Elecraft]

Please excuse me if this information has been given already.
I spoke to Wayne N6KR  at Dayton a few years ago about the KAT3.
To clear all memories in the KAT3:
While in Config:KAT3, tap the "CLR" button on the K3 panel. (This is per band)
Tune KAT3 into a dummy load - each band to re-establish memory.
73, Jim Douglas   K2ZF
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Re: [Elecraft] K3 SWR Anomaly

[Ed G]

Hi Mike,
 Have not heard from Support yet.  But this is an interesting discussion 
and I am learning some things from the group.  I had not kept up with the 
differences between the KAT3 and the KAT3A, but it would seem that’s at the 
center of the issue I have.
 My K3 is S/N 02977, and I have the KAT3 tuner.  Apparently the KAT3 is not 
really bypassed in the BYPASS position. From reading earlier posts, the KAT3 
supposedly sets itself for what it thinks is a 50 ohm match when in the BYPASS 
position. It was suggested by Joe, W4TV, that the user could enable the tuner, 
tune into a dummy load and then bypass the tuner, and that process would reset 
the bypass settings.That seems to have worked for me on 10 meters, but not 
on 40 meters.  So part of my original post has been answered, but here’s what 
remains:

1. With my particular KAT3, I am not sure why the recal of bypass settings per 
W4TV does not work on 40 meters.
2. If the KAT3 is not truly being bypassed, can there be some unexpected 
results when using the K3 with the KPA1500, such as power overshoot?
3. Am I ok to enable the KAT3 in my K3 and also use the tuner in the KPA1500?  
Otherwise I am having to readjust the K3 power out setting as I change 
frequency on 40 meters, to keep from overdriving the KPA1500.

It would appear that I might have some unknown tuner circuit issue when 
bypassing the tuner on 40 meters due to whatever is still in the RF path, or 
perhaps even the faulty trap component Mike mentioned.  Elecraft – do I need to 
replace the KAT3 with the KAT3A to get rid of this problem, and eliminate the 
need to readjust power up when using my KPA1500? I appreciate all the responses 
so far!

--Ed—

Sent from Mail for Windows 10

From: Mike Wetzel
Sent: Monday, January 21, 2019 1:33 PM
To: ed.n...@gmail.com
Subject: K3 SWR

Ed,

I’m sure you have heard from Elecraft Support on this but just in case.  I had 
a very similar problem on 40 meter a couple of years ago.  It turned out to be 
a faulty trap component on a nearly vacant board near the ant terminals.   The 
trap is not needed I removed a cap and all has been fine ever since.

Mike W9RE


 I think what I am seeing is related to your experience. I ran through some 
additional testing. I see perhaps some slight differences between ANT1 and ANT2 
positions as far as SWR readings, but nothing significant, at least on 40 
meters.
     I do now see something I?m even more puzzled over. While collecting SWR 
readings into a dummy load on 10 meters, I initially did see a high (2.0:1) 
reading on the K3 meter. I switched in the K3 tuner, and brought the SWR down 
to 1:1.  But when I then bypassed the tuner, the low 1:1 SWR remained.  This 
was true for either ANT1 or ANT2.  I really don?t understand that.
 So back to 40 meters, where I first noticed the high SWR anomaly. I 
thought I would try the tuner again, and then bypass it, to see if SWR would 
stay low on the K3 meter as it did on 10 meters.  It did not.  So I still have 
the anomaly on 40 meters, and it is the same on either ANT1 or ANT2 positions.  
 To summarize:
1.  SWR using a dummy load on 40 meters remains constant using an external 
LP-100A meter, but varies greatly using the K3 meter. As you tune up in 
frequency on the 40 meter band, the SWR on the K3 meter rises to almost 3:1, 
and the K3 output power drops back significantly. 
2. Antenna tuner settings appear to ?stick? on 10 meters, even when the tuner 
is bypassed.

I believe some users, assuming there are others that have K3s which would 
exhibit this behavior, may not have noticed this anomaly. I do believe it may 
be responsible for what some users have noticed when using their K3 with an amp 
such as the KPA1500. That is, power overshoot. I suspect the K3, at least for 
me on 40 meters, is folding back power in response to a false SWR reading, and 
this can be seen in how the KPA1500 amp correspondingly drops back in power as 
the user transmits.  That is perhaps why (again, for my situation) I see the 
power overshoot only on 40 meters when using my KPA1500.
--Ed?





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Re: [Elecraft] K3 SWR Anomaly

[Mike Harris via Elecraft]

Looking at the KAT3 schematic indicates that in bypass all the relays 
are set such that all the series inductors are individually short 
circuited and all the capacitors are open circuit. This potentially 
introduces strays due to the short circuit inductors, relays and pcb 
tracks still in the RF path.


I believe it is mentioned on the Elecraft web site that this is the 
reason for the KAT3A having a "true bypass" or words to that effect.


It was suggested that you could tune out the strays by tuning the ATU 
into a dummy load rather than simply putting it in bypass.


I've just checked my KAT3 action by tuning each band via the Ant1 port 
into an Oak Hills Research 100W dummy load and comparing the result with 
simply bypassing it.


All the way from 160m to 10m both states "Auto" and "Bypass" read 1.0-1
On 6m both read 1.1-1.

I normally have the KAT3 in "bypass" given that much of the time my K3 
is looking at the input circuit of an Acom 1000 or the antennas are 
already an acceptable match. There were clearly some long forgotten 
tuning solutions still sitting in the atu memory which were tuned out 
whilst feeding the dummy load.


Regards,

Mike VP8NO

On 21/01/2019 12:40, Grant Youngman wrote:

The revised KAT3A has a hard bypass with relays.  The KAT3 does a “soft” bypass 
by placing the tuning network in some kind of neutral position.

I don’t know what the KAT3 actually does to achieve this, but is it possible 
this is somehow related to the anomaly you are seeing?  With the KAT3 in  
“neutral” (whatever that actually means), since the SWR bridge sits between the 
KPA3 output and the KAT3 input, maybe that’s something to look at — or at least 
get more info from Elecraft about how it works and if that might be related.

Grant NQ5T
K3 #2091 KX3 #8342


On Jan 21, 2019, at 8:34 AM, Ed G  wrote:

Hi Barry,
 I think what I am seeing is related to your experience. I ran through some 
additional testing. I see perhaps some slight differences between ANT1 and ANT2 
positions as far as SWR readings, but nothing significant, at least on 40 
meters.
 I do now see something I’m even more puzzled over. While collecting SWR 
readings into a dummy load on 10 meters, I initially did see a high (2.0:1) 
reading on the K3 meter. I switched in the K3 tuner, and brought the SWR down 
to 1:1.  But when I then bypassed the tuner, the low 1:1 SWR remained.  This 
was true for either ANT1 or ANT2.  I really don’t understand that.
 So back to 40 meters, where I first noticed the high SWR anomaly. I 
thought I would try the tuner again, and then bypass it, to see if SWR would 
stay low on the K3 meter as it did on 10 meters.  It did not.  So I still have 
the anomaly on 40 meters, and it is the same on either ANT1 or ANT2 positions.
 To summarize:
1.  SWR using a dummy load on 40 meters remains constant using an external 
LP-100A meter, but varies greatly using the K3 meter. As you tune up in 
frequency on the 40 meter band, the SWR on the K3 meter rises to almost 3:1, 
and the K3 output power drops back significantly.
2. Antenna tuner settings appear to “stick” on 10 meters, even when the tuner 
is bypassed.

I believe some users, assuming there are others that have K3s which would 
exhibit this behavior, may not have noticed this anomaly. I do believe it may 
be responsible for what some users have noticed when using their K3 with an amp 
such as the KPA1500. That is, power overshoot. I suspect the K3, at least for 
me on 40 meters, is folding back power in response to a false SWR reading, and 
this can be seen in how the KPA1500 amp correspondingly drops back in power as 
the user transmits.  That is perhaps why (again, for my situation) I see the 
power overshoot only on 40 meters when using my KPA1500.
--Ed—

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Re: [Elecraft] K3 SWR Anomaly

[Grant Youngman]

The revised KAT3A has a hard bypass with relays.  The KAT3 does a “soft” bypass 
by placing the tuning network in some kind of neutral position.

I don’t know what the KAT3 actually does to achieve this, but is it possible 
this is somehow related to the anomaly you are seeing?  With the KAT3 in  
“neutral” (whatever that actually means), since the SWR bridge sits between the 
KPA3 output and the KAT3 input, maybe that’s something to look at — or at least 
get more info from Elecraft about how it works and if that might be related.

Grant NQ5T
K3 #2091 KX3 #8342

> On Jan 21, 2019, at 8:34 AM, Ed G  wrote:
> 
> Hi Barry,
> I think what I am seeing is related to your experience. I ran through 
> some additional testing. I see perhaps some slight differences between ANT1 
> and ANT2 positions as far as SWR readings, but nothing significant, at least 
> on 40 meters.
> I do now see something I’m even more puzzled over. While collecting SWR 
> readings into a dummy load on 10 meters, I initially did see a high (2.0:1) 
> reading on the K3 meter. I switched in the K3 tuner, and brought the SWR down 
> to 1:1.  But when I then bypassed the tuner, the low 1:1 SWR remained.  This 
> was true for either ANT1 or ANT2.  I really don’t understand that.
> So back to 40 meters, where I first noticed the high SWR anomaly. I 
> thought I would try the tuner again, and then bypass it, to see if SWR would 
> stay low on the K3 meter as it did on 10 meters.  It did not.  So I still 
> have the anomaly on 40 meters, and it is the same on either ANT1 or ANT2 
> positions.  
> To summarize:
> 1.  SWR using a dummy load on 40 meters remains constant using an external 
> LP-100A meter, but varies greatly using the K3 meter. As you tune up in 
> frequency on the 40 meter band, the SWR on the K3 meter rises to almost 3:1, 
> and the K3 output power drops back significantly. 
> 2. Antenna tuner settings appear to “stick” on 10 meters, even when the tuner 
> is bypassed.
> 
> I believe some users, assuming there are others that have K3s which would 
> exhibit this behavior, may not have noticed this anomaly. I do believe it may 
> be responsible for what some users have noticed when using their K3 with an 
> amp such as the KPA1500. That is, power overshoot. I suspect the K3, at least 
> for me on 40 meters, is folding back power in response to a false SWR 
> reading, and this can be seen in how the KPA1500 amp correspondingly drops 
> back in power as the user transmits.  That is perhaps why (again, for my 
> situation) I see the power overshoot only on 40 meters when using my KPA1500.
> --Ed—
> 

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Re: [Elecraft] K3 SWR Anomaly

[Eric Norris]

Have you done a TX GAIN CAL procedure?  I have found this often solves
quirky problems that have cropped up with my K3 over the past 10 years.

Also, if you are getting power overshoot, check to be sure your MIC or LINE
IN is not set higher than 4 bars with the 5th bar flashing on the ALC meter.

73 Eric WD6DBM

On Mon, Jan 21, 2019, 5:36 AM Ed G  Hi Barry,
>  I think what I am seeing is related to your experience. I ran through
> some additional testing. I see perhaps some slight differences between ANT1
> and ANT2 positions as far as SWR readings, but nothing significant, at
> least on 40 meters...


>
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[Elecraft] K3 SWR Anomaly

[Ed G]

Hi Barry,
 I think what I am seeing is related to your experience. I ran through some 
additional testing. I see perhaps some slight differences between ANT1 and ANT2 
positions as far as SWR readings, but nothing significant, at least on 40 
meters.
 I do now see something I’m even more puzzled over. While collecting SWR 
readings into a dummy load on 10 meters, I initially did see a high (2.0:1) 
reading on the K3 meter. I switched in the K3 tuner, and brought the SWR down 
to 1:1.  But when I then bypassed the tuner, the low 1:1 SWR remained.  This 
was true for either ANT1 or ANT2.  I really don’t understand that.
 So back to 40 meters, where I first noticed the high SWR anomaly. I 
thought I would try the tuner again, and then bypass it, to see if SWR would 
stay low on the K3 meter as it did on 10 meters.  It did not.  So I still have 
the anomaly on 40 meters, and it is the same on either ANT1 or ANT2 positions.  
 To summarize:
1.  SWR using a dummy load on 40 meters remains constant using an external 
LP-100A meter, but varies greatly using the K3 meter. As you tune up in 
frequency on the 40 meter band, the SWR on the K3 meter rises to almost 3:1, 
and the K3 output power drops back significantly. 
2. Antenna tuner settings appear to “stick” on 10 meters, even when the tuner 
is bypassed.

I believe some users, assuming there are others that have K3s which would 
exhibit this behavior, may not have noticed this anomaly. I do believe it may 
be responsible for what some users have noticed when using their K3 with an amp 
such as the KPA1500. That is, power overshoot. I suspect the K3, at least for 
me on 40 meters, is folding back power in response to a false SWR reading, and 
this can be seen in how the KPA1500 amp correspondingly drops back in power as 
the user transmits.  That is perhaps why (again, for my situation) I see the 
power overshoot only on 40 meters when using my KPA1500.
--Ed—



Sent from Mail for Windows 10

From: Barry Simpson
Sent: Monday, January 21, 2019 1:51 AM
To: Ed G; Elecraft Mailing List
Subject: Re: [Elecraft] K3 SWR Question3

Hi Ed

I recall having had a similar experience with my K3 some years ago, although it 
wasn't on 40m. I think it was either 10 or 12m and related to an antenna 
connected to the ANT 1 socket.

Eventually I tracked it down to having previously had an antenna connected to 
the ANT 2 socket and having used the ATU in the K3 to tune it at that time 
although I think that there was no antenna on ANT 2 when the problem cropped up.

I believe that the feed through between ANT 1 and 2 sockets was sufficient to 
give a false SWR reading on the K3.

It might be worth investigating this and possibly swapping over your 
antenna/dummy load to the ANT 2 socket to see what happens.

I think I eventually just retuned the ATU on ANT 2 with a dummy load in place 
and the problem went away.

Good luck.

Barry  VK2BJ

On Mon, 21 Jan 2019 at 04:17, Ed G  wrote:
Hello,
     My K3 is exhibiting some SWR meter behavior I don’t quite understand. To 
eliminate any possible effects of antennas or cabling, I hooked a Palstar DL2K 
dummy load directly to the K3 antenna connector. All bands except 40 meters 
seem fine, with SWR reading as you would expect with a dummy load. The anomaly 
I am seeing is that SWR as shown on the K3 meter looks fine at 7.01 MHz 
(approx. 1.2:1), but as I go up in frequency, the SWR as shown on the K3 meter 
rises. When I transmit into the dummy load on 7.298 MHz, the K3 meter reads 
almost 3:1.   I can switch in the K3 internal tuner and bring the SWR down to 
1:1.  
     I also tried an older Cantenna dummy load with the same puzzling results.  
Any ideas as to what may be causing this 40 meter only problem?  I first 
noticed this problem during NAQP SSB when using my Steppir, which of course 
retunes itself as I change frequency. When going from the low part of the phone 
band to the high part on 40 meters, I noticed SWR increasing on the K3 meter, 
even though it was not increasing and stayed at 1.2:1 on my inline LP-100A.  
The K3 also started to fold back power.  That prompted me to do the further 
testing with the dummy load as I discussed above.
--Ed—


Sent from Mail for Windows 10




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Please help

Re: [Elecraft] K3 SWR Question3

[Barry Simpson]

Hi Ed

I recall having had a similar experience with my K3 some years ago,
although it wasn't on 40m. I think it was either 10 or 12m and related to
an antenna connected to the ANT 1 socket.

Eventually I tracked it down to having previously had an antenna connected
to the ANT 2 socket and having used the ATU in the K3 to tune it at that
time although I think that there was no antenna on ANT 2 when the problem
cropped up.

I believe that the feed through between ANT 1 and 2 sockets was sufficient
to give a false SWR reading on the K3.

It might be worth investigating this and possibly swapping over your
antenna/dummy load to the ANT 2 socket to see what happens.

I think I eventually just retuned the ATU on ANT 2 with a dummy load in
place and the problem went away.

Good luck.

Barry  VK2BJ

On Mon, 21 Jan 2019 at 04:17, Ed G  wrote:

> Hello,
>  My K3 is exhibiting some SWR meter behavior I don’t quite understand.
> To eliminate any possible effects of antennas or cabling, I hooked a
> Palstar DL2K dummy load directly to the K3 antenna connector. All bands
> except 40 meters seem fine, with SWR reading as you would expect with a
> dummy load. The anomaly I am seeing is that SWR as shown on the K3 meter
> looks fine at 7.01 MHz (approx. 1.2:1), but as I go up in frequency, the
> SWR as shown on the K3 meter rises. When I transmit into the dummy load on
> 7.298 MHz, the K3 meter reads almost 3:1.   I can switch in the K3 internal
> tuner and bring the SWR down to 1:1.
>  I also tried an older Cantenna dummy load with the same puzzling
> results.  Any ideas as to what may be causing this 40 meter only problem?
> I first noticed this problem during NAQP SSB when using my Steppir, which
> of course retunes itself as I change frequency. When going from the low
> part of the phone band to the high part on 40 meters, I noticed SWR
> increasing on the K3 meter, even though it was not increasing and stayed at
> 1.2:1 on my inline LP-100A.  The K3 also started to fold back power.  That
> prompted me to do the further testing with the dummy load as I discussed
> above.
> --Ed—
>
>
> Sent from Mail for Windows 10
>
>
>
>
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[Elecraft] K3 SWR Question3

[Ed G]

Hello,
 My K3 is exhibiting some SWR meter behavior I don’t quite understand. To 
eliminate any possible effects of antennas or cabling, I hooked a Palstar DL2K 
dummy load directly to the K3 antenna connector. All bands except 40 meters 
seem fine, with SWR reading as you would expect with a dummy load. The anomaly 
I am seeing is that SWR as shown on the K3 meter looks fine at 7.01 MHz 
(approx. 1.2:1), but as I go up in frequency, the SWR as shown on the K3 meter 
rises. When I transmit into the dummy load on 7.298 MHz, the K3 meter reads 
almost 3:1.   I can switch in the K3 internal tuner and bring the SWR down to 
1:1.  
 I also tried an older Cantenna dummy load with the same puzzling results.  
Any ideas as to what may be causing this 40 meter only problem?  I first 
noticed this problem during NAQP SSB when using my Steppir, which of course 
retunes itself as I change frequency. When going from the low part of the phone 
band to the high part on 40 meters, I noticed SWR increasing on the K3 meter, 
even though it was not increasing and stayed at 1.2:1 on my inline LP-100A.  
The K3 also started to fold back power.  That prompted me to do the further 
testing with the dummy load as I discussed above.
--Ed—


Sent from Mail for Windows 10




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Re: [Elecraft] [K3] SWR - Numerical Indication

[ANDY DURBIN]

"Do you find a high degree of correlation between your (assumed) K3 and KAT500 
SWR readings across various levels of SWR? "

I don't have a K3.  I do have loads of recorded data that would allow 
comparison of KPA500 SWR and LP-100A SWR and a more limited set of data that 
would allow comparison of KAT500 SWR with LP-100A SWR.  I have not performed 
either comparison but, as a general observation, it's obvious that the LP-100A 
is far more useful at low power levels or for mismatches that would give low 
reflected power.  At high power levels there is quite good agreement between 
the LP-100A and the KPA500 for power and SWR.  Since I know that, I look mainly 
at the LP-100A data.

I did a quick test on 20 m.  For an antenna system load that my LP-100A reports 
as SWR 1.09 with  Z of 52.7 ohm at 4.3 deg it took about 70 W output power for 
my KAT500 to change from 1.00 to 1.11 SWR.

To look at this another way - until the meter moves off the peg it isn't 
telling you much about the signal being measured.  All it's telling you is that 
you need a better meter.

I'm not saying there is anything wrong with the KPA500 or KAT500 SWR metering.  
You just need to know how it behaves and what it is useful for.  I expect the 
same applies to the K3 SWR meter.

Andy, k3wyc

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Re: [Elecraft] [K3] SWR - Numerical Indication

[John Oppenheimer]

Hi Dick,

The Elecraft list does not accept attachments. Send to me directly.

John KN5L

On 12/2/18 4:14 PM, Dick Dickinson wrote:
> Hi John,
> 
> Per your suggestion, I ran a sweep of my 40 meter vertical with the K3 /
> K3EZ software.
> 
> I then measured at ~20 kHz steps with my MFJ-259B.
> Both sets of measurements were taken from the PL-259 that plugs into the rig
> or 259B.
> 
> Conditions were ~60 degrees F, ground nearly saturated.
> 
> Attached is an image of the results.
> 
> Kindly,
> Dick - KA5KKT
> 
> 
> ---
> 
> Hi Dick,
> 
> An EZNEC and SimSmith model of the on ground 1/4 wave vertical:
> https://www.kn5l.net/images/SS-KA5KKT-vertical.png
> 
> SimSmith R1 represents ground loss, the value set to establish a 50 ohm load
> at the transmitter, G in SimSmith.
> 
> According to the models, the 7 to 7.3 MHz SWR is a little below 1.3.
> 
> A flat measurement using the K3 SWR meter seams reasonable. My suggestion is
> to use a Antenna Analyzer to measure the antenna and system.
> 
> John KN5L
> 
> On 12/2/18 12:16 AM, Dick Dickinson wrote:
>> I have a full-size monoband vertical for 40 meters.  Simple 
>> architectural aluminum tapering from 1 �� (?) in 6� telescoping 
>> sections.  The radial field is designed to provide a 50 ohm match at 
>> the feed point�12 � 13�+ radials.  It is fed directly�no matching 
>> device with RG-213 from the remote antenna switch about 50� away at my 
>> tower.  The coax from the rig to the remote antenna switch is 
>> estimated to be ~ 50� in length.  A lot of the time running K3EZ to 
>> sweep the band (typically 20 watts), it will indicate a
>> 1.0:1 SWR from 7.0 MHz to 7.3 MHz in 20 kHz steps.  Occasional 
>> deviation from one K3EZ run to another might be due to variations in 
>> moisture content of the ground or less than perfect connection to the 
>> vertical�an uncommon situation.  The K3 shows the same readings.
>>
>> Is this 1.0:1 SWR across the entire 40 meter band curious or remarkable?

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[Elecraft] [K3] SWR - Numerical Indication

[Dick Dickinson]

Hi Andy,

 

Thanks for sharing your thoughts.

 

Do you find a high degree of correlation between your (assumed) K3 and
KAT500 SWR readings across various levels of SWR?  

 

 

Kindly,

Dick - KA5KKT 

ANDY DURBIN
 a.durbin at
msn.com 
Sun Dec 2 15:13:21 EST 2018 

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"Is this 1.0:1 SWR across the entire 40 meter band curious or remarkable?"

 

I'd guess that it's improbable and likely the result of measurement error.
The reflected voltage will be zero for low or high power if the antenna
system is a perfect match .  However, the (measured) reflected voltage will
also be zero for an imperfectly matched antenna system when there is not
enough power for the reflected voltage to be above the detection threshold
on the measurement device.The Elecraft SWR meters that I have (KPA500
and KAT500) will indicate SWR 1.0:1 with no forward voltage and also with
some forward voltage and no reflected voltage.   You have to know when to
believe the reading and that may be only when the reading is not 1.0:1.

 

Running the sweep with higher power may give quite different results, but
running high power antenna sweeps may be considered anti-social.An
antenna analyzer will probably give a much better indication of your antenna
system characteristics.

 

Andy, k3wyc

 

  _  

 

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Re: [Elecraft] [K3] SWR - Numerical Indication

[Dick Dickinson]

Hi John,

 

Per your suggestion, I ran a sweep of my 40 meter vertical with the K3 /
K3EZ software.

I then measured at ~20 kHz steps with my MFJ-259B.

Both sets of measurements were taken from the PL-259 that plugs into the rig
or 259B.

 

Conditions were ~60 degrees F, ground nearly saturated.

 

Attached is an image of the results.

 

 

Kindly,

Dick - KA5KKT


---

Hi Dick,

 

An EZNEC and SimSmith model of the on ground 1/4 wave vertical:

https://www.kn5l.net/images/SS-KA5KKT-vertical.png

 

SimSmith R1 represents ground loss, the value set to establish a 50 ohm load
at the transmitter, G in SimSmith.

 

According to the models, the 7 to 7.3 MHz SWR is a little below 1.3.

 

A flat measurement using the K3 SWR meter seams reasonable. My suggestion is
to use a Antenna Analyzer to measure the antenna and system.

 

John KN5L

 

On 12/2/18 12:16 AM, Dick Dickinson wrote:

> I have a full-size monoband vertical for 40 meters.  Simple 

> architectural aluminum tapering from 1 ¼” (?) in 6’ telescoping 

> sections.  The radial field is designed to provide a 50 ohm match at 

> the feed point…12 – 13’+ radials.  It is fed directly…no matching 

> device with RG-213 from the remote antenna switch about 50’ away at my 

> tower.  The coax from the rig to the remote antenna switch is 

> estimated to be ~ 50’ in length.  A lot of the time running K3EZ to 

> sweep the band (typically 20 watts), it will indicate a

> 1.0:1 SWR from 7.0 MHz to 7.3 MHz in 20 kHz steps.  Occasional 

> deviation from one K3EZ run to another might be due to variations in 

> moisture content of the ground or less than perfect connection to the 

> vertical…an uncommon situation.  The K3 shows the same readings.

> 

> Is this 1.0:1 SWR across the entire 40 meter band curious or remarkable?

 

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[Elecraft] [K3] SWR - Numerical Indication

[ANDY DURBIN]

"Is this 1.0:1 SWR across the entire 40 meter band curious or remarkable?"

I'd guess that it's improbable and likely the result of measurement error.  The 
reflected voltage will be zero for low or high power if the antenna system is a 
perfect match .  However, the (measured) reflected voltage will also be zero 
for an imperfectly matched antenna system when there is not enough power for 
the reflected voltage to be above the detection threshold on the measurement 
device.The Elecraft SWR meters that I have (KPA500 and KAT500) will 
indicate SWR 1.0:1 with no forward voltage and also with some forward voltage 
and no reflected voltage.   You have to know when to believe the reading and 
that may be only when the reading is not 1.0:1.

Running the sweep with higher power may give quite different results, but 
running high power antenna sweeps may be considered anti-social.An antenna 
analyzer will probably give a much better indication of your antenna system 
characteristics.

Andy, k3wyc

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Re: [Elecraft] [K3] SWR - Numerical Indication

[Bob McGraw K4TAX]

What is VSWR? There are many misconceptions and myths about VSWR. To try to 
overcome some of these misconceptions and to try to provide an easy and 
understandable summary, Electronics Notes has developed a page describing what 
VSWR is and this is accompanied by an embedded video.

The page and video describe how a perfect match means that all the power is 
absorbed by the load, and it then goes on to show what happens when there is a 
mismatch. The case of the open and short circuits are used to show the extreme 
situations and then these are developed to show what happens with loads that 
are less than or greater then the characteristic impedance of the feeder.

Understanding how the reflected power gives rise to voltage and current 
standing waves is the key to understanding what happens when there is a high 
VSWR.

Read all about VSWR:
https://www.electronics-notes.com/articles/antennas-propagation/vswr-return-loss/what-is-vswr.php

Watch the video:
https://youtu.be/BSa051lWB.c om 





73
Bob, K4TAX


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Re: [Elecraft] [K3] SWR - Numerical Indication

[John Oppenheimer]

Hi Dick,

An EZNEC and SimSmith model of the on ground 1/4 wave vertical:
https://www.kn5l.net/images/SS-KA5KKT-vertical.png

SimSmith R1 represents ground loss, the value set to establish a 50 ohm
load at the transmitter, G in SimSmith.

According to the models, the 7 to 7.3 MHz SWR is a little below 1.3.

A flat measurement using the K3 SWR meter seams reasonable. My
suggestion is to use a VNA to measure the antenna and system.

John KN5L

On 12/2/18 12:16 AM, Dick Dickinson wrote:
> Thanks for the explanation,  John.
> 
> I’m not an electronically educated fellow, merely just seeking the
> practical.  
> 
> A resolution to my post was provided in the suggestion that the apparent
> 1.1:1 SWR might be the result of common mode current.  Sure enough when I
> installed a 1:1 current balun at the feed point of the antennas (2
> perpendicular Inverted Vees with a switchable common feed point), the value
> went from 1.1:1 to 1.0:1 and the bottom of the SWR curves which also
> broadened out.
> 
> Still that doesn’t explain why the K3 was showing 1.1:1 while passing 1.0:1
> information to K3EZ, or so it seems.  I don’t think that the K3EZ is
> ‘measuring SWR’ rather merely posting information it is getting from the
> K3…no different measuring device or location.  Perhaps it is a sort of
> ‘rounding error.’  By the way, for those who haven’t come across it, K3EZ
> has the great feature of being able to step the K3 across a frequency range,
> momentarily key it, step again, etc. and plot in text an SWR chart…a handy
> feature for working with an antenna installation.
> 
> Following is a situation that perhaps you have the theoretical background to
> explain…
> 
> I have a full-size monoband vertical for 40 meters.  Simple architectural
> aluminum tapering from 1 ¼” (?) in 6’ telescoping sections.  The radial
> field is designed to provide a 50 ohm match at the feed point…12 – 13’+
> radials.  It is fed directly…no matching device with RG-213 from the remote
> antenna switch about 50’ away at my tower.  The coax from the rig to the
> remote antenna switch is estimated to be ~ 50’ in length.  A lot of the time
> running K3EZ to sweep the band (typically 20 watts), it will indicate a
> 1.0:1 SWR from 7.0 MHz to 7.3 MHz in 20 kHz steps.  Occasional deviation
> from one K3EZ run to another might be due to variations in moisture content
> of the ground or less than perfect connection to the vertical…an uncommon
> situation.  The K3 shows the same readings.
> 
> Is this 1.0:1 SWR across the entire 40 meter band curious or remarkable?
> 
> Dick – KA5KKT
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Re: [Elecraft] [K3] SWR - Numerical Indication

[John Oppenheimer]

Hi Dick,

An EZNEC and SimSmith model of the on ground 1/4 wave vertical:
https://www.kn5l.net/images/SS-KA5KKT-vertical.png

SimSmith R1 represents ground loss, the value set to establish a 50 ohm
load at the transmitter, G in SimSmith.

According to the models, the 7 to 7.3 MHz SWR is a little below 1.3.

A flat measurement using the K3 SWR meter seams reasonable. My
suggestion is to use a Antenna Analyzer to measure the antenna and system.

John KN5L

On 12/2/18 12:16 AM, Dick Dickinson wrote:
> I have a full-size monoband vertical for 40 meters.  Simple architectural
> aluminum tapering from 1 ¼” (?) in 6’ telescoping sections.  The radial
> field is designed to provide a 50 ohm match at the feed point…12 – 13’+
> radials.  It is fed directly…no matching device with RG-213 from the remote
> antenna switch about 50’ away at my tower.  The coax from the rig to the
> remote antenna switch is estimated to be ~ 50’ in length.  A lot of the time
> running K3EZ to sweep the band (typically 20 watts), it will indicate a
> 1.0:1 SWR from 7.0 MHz to 7.3 MHz in 20 kHz steps.  Occasional deviation
> from one K3EZ run to another might be due to variations in moisture content
> of the ground or less than perfect connection to the vertical…an uncommon
> situation.  The K3 shows the same readings.
> 
> Is this 1.0:1 SWR across the entire 40 meter band curious or remarkable?
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Re: [Elecraft] [K3] SWR - Numerical Indication

[Dick Dickinson]

Thanks for the explanation,  John.

 

I’m not an electronically educated fellow, merely just seeking the
practical.  

 

A resolution to my post was provided in the suggestion that the apparent
1.1:1 SWR might be the result of common mode current.  Sure enough when I
installed a 1:1 current balun at the feed point of the antennas (2
perpendicular Inverted Vees with a switchable common feed point), the value
went from 1.1:1 to 1.0:1 and the bottom of the SWR curves which also
broadened out.

 

Still that doesn’t explain why the K3 was showing 1.1:1 while passing 1.0:1
information to K3EZ, or so it seems.  I don’t think that the K3EZ is
‘measuring SWR’ rather merely posting information it is getting from the
K3…no different measuring device or location.  Perhaps it is a sort of
‘rounding error.’  By the way, for those who haven’t come across it, K3EZ
has the great feature of being able to step the K3 across a frequency range,
momentarily key it, step again, etc. and plot in text an SWR chart…a handy
feature for working with an antenna installation.

 

Following is a situation that perhaps you have the theoretical background to
explain…

 

I have a full-size monoband vertical for 40 meters.  Simple architectural
aluminum tapering from 1 ¼” (?) in 6’ telescoping sections.  The radial
field is designed to provide a 50 ohm match at the feed point…12 – 13’+
radials.  It is fed directly…no matching device with RG-213 from the remote
antenna switch about 50’ away at my tower.  The coax from the rig to the
remote antenna switch is estimated to be ~ 50’ in length.  A lot of the time
running K3EZ to sweep the band (typically 20 watts), it will indicate a
1.0:1 SWR from 7.0 MHz to 7.3 MHz in 20 kHz steps.  Occasional deviation
from one K3EZ run to another might be due to variations in moisture content
of the ground or less than perfect connection to the vertical…an uncommon
situation.  The K3 shows the same readings.

 

Is this 1.0:1 SWR across the entire 40 meter band curious or remarkable?

 

 

Dick – KA5KKT

 

 


--

 

Hi Dick,

 

Some numbers: using the K3 Schematic, "K3S RF Board" Sheet 2, Section

B1. The power meter uses a series Schottky diode detector. The low

reasonable resolution is about 0.3 VDC, or 0.3 * .707 = 0.21 Vrms out of

the directional coupler.

 

The Power for 0.21 Vrms is:

0.21^2 / 50 = .88 mW

Assuming a 20 dB coupler 1:10 turns ratio, 0.88mW * 100 = 0.88W

reflected power.

 

Assuming forward power of 100 watts and 0.88 watt reflected power the

return loss is:

10 * log(100 / 0.88) = 20.6 dB

 

Using the calculator:

https://www.allaboutcircuits.com/tools/vswr-return-loss-calculator/

20.6 dB Return Loss computes to VSWR = 1.222

 

Therefore, the best lowest estimated K3 VSWR, assuming a 20 dB coupler,

is about 1.2.

 

Check my numbers.

 

John KN5L

 

 

On 7/27/18 9:58 AM, Dick Dickinson wrote:

> I've noticed that I'm not showing a reading of less than 1.1:1 SWR on my

> antennas per K3 SWR Numerical Readout.  K3EZ will record 1.0:1 SWR in band

> sweeps.

> 

> Can the K3(S) Numerical Display show 1.0:1 SWR?  If so, is there a likely

> reason why K3EZ will show 1.0:1 while my K3 will only go as far down as

> 1.1:1?

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Re: [Elecraft] [K3] SWR - Numerical Indication

[John Oppenheimer]

Hi Dick,

Some numbers: using the K3 Schematic, "K3S RF Board" Sheet 2, Section
B1. The power meter uses a series Schottky diode detector. The low
reasonable resolution is about 0.3 VDC, or 0.3 * .707 = 0.21 Vrms out of
the directional coupler.

The Power for 0.21 Vrms is:
0.21^2 / 50 = .88 mW
Assuming a 20 dB coupler 1:10 turns ratio, 0.88mW * 100 = 0.88W
reflected power.

Assuming forward power of 100 watts and 0.88 watt reflected power the
return loss is:
10 * log(100 / 0.88) = 20.6 dB

Using the calculator:
https://www.allaboutcircuits.com/tools/vswr-return-loss-calculator/
20.6 dB Return Loss computes to VSWR = 1.222

Therefore, the best lowest estimated K3 VSWR, assuming a 20 dB coupler,
is about 1.2.

Check my numbers.

John KN5L


On 7/27/18 9:58 AM, Dick Dickinson wrote:
> I've noticed that I'm not showing a reading of less than 1.1:1 SWR on my
> antennas per K3 SWR Numerical Readout.  K3EZ will record 1.0:1 SWR in band
> sweeps.
> 
> Can the K3(S) Numerical Display show 1.0:1 SWR?  If so, is there a likely
> reason why K3EZ will show 1.0:1 while my K3 will only go as far down as
> 1.1:1?
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Re: [Elecraft] [K3] SWR - Numerical Indication

[Dave Hachadorian]

This discussion reminds me of a lesson in engineering class (55 
years ago) about the difference between precision and accuracy. 
The professor used the example of bullet holes in a target.


If the holes were closely spaced, but far from the bulls-eye, the 
shooter was inaccurate but precise.


If the holes were widely spaced, but the average was near the 
bulls-eye the shooter was accurate but imprecise.


Closely spaced on the bulls-eye precise and accurate

Widely spaced, and the average not near the bulls-eye, imprecise 
and inaccurate.


Easy to remember.

Some other memorable nuggets from that class:
Evaporation is a cooling process.
High octane gasoline is slow-burning gasoline.
The electric company bills you for kilowatt-hours, so they are 
not a power company, they are an energy company.



Dave Hachadorian, K6LL
Yuma, AZ


-Original Message- 
From: Don Wilhelm

Sent: Friday, November 30, 2018 7:55 AM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] [K3] SWR - Numerical Indication

Petr and all,

Those digital instruments that show 2, 3, or 4 decimal places 
have given

us a false sense of accuracy.
For instance an instrument that is accurate to 5% and has a 4 
digit
display can show us (when measuring a 5 volt source) anywhere 
between
4.750 volts and 5.250 volts and still be within the 5% accuracy 
window

for the instrument.

Review the specs and calibration for whatever meter you are using 
and do
not expect those extra digits to be correct - in other words 
round the

numbers displayed.

Many wattmeters are only accurate to 20% of the reading - so if 
one
wattmeter at 100 watts shows 120 watts and another shows 80 
watts, the

actual power could be 100 watts.  Take that into consideration.

The Telepost LP-100 when calibrated to NIST standards is accurate 
to 5%
(it can be lower, but Larry will not guarantee it).  So any power 
it

displays between 95 and 105 watts can actually be 100 watts.

In other words, look at the specified accuracy of whatever meter 
you are
using and take that into consideration.  Those extra digits on 
your

meter may be meaningless.

73,
Don W3FPR

On 11/30/2018 9:29 AM, Petr, OK1RP/M0SIS wrote:

Hi Wes,

excellent!

Many thanks for this post which is nicely explaining what is 
going on about

the measurement in K3s.

In fact until now no one talked about the calibrations, 
uncertainties,
errors, accuracy, reading errors, uncertainties A, B and 
combined
uncertainties etc. In that case there is several error sources 
and factors
which need to be calculated in order to get some more precise 
values ...and
in all cases the uncertainties must be calculated together with 
measured
value if we would like to talk about scientific or 
sophisticated

measurement.

Thanks for nice explanation Wes to all.

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Re: [Elecraft] [K3] SWR - Numerical Indication

[Phil Kane]

On 11/30/2018 8:12 AM, Charlie T wrote:

> it was better when we only had slide-rules to calculate things.

And we had to have "situational awareness" of the order of magnitude of
the result.
"What is the relationship between a megaphone and a microphone?"  Answer
- 10^12

Back on topic - what is the "advertised accuracy" of the KAT100 SWR bridge?

73 de K2ASP - Phil Kane
Elecraft K2/100   s/n 5402

>From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon
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Re: [Elecraft] [K3] SWR - Numerical Indication

[Don Wilhelm]

All,

There is a big difference between accuracy and precision.
Precision can be accomplished by adding the extra digits, but the 
accuracy of the instrument will tell you how many of those extra digits 
are to be considered.


Most digital voltmeters, even the cheap or free ones from Harbor Freight 
and others are surprisingly accurate (5% or so is common), but typical 
voltage readings of 3 significant digits are reasonable but any digits 
more than that are extraneous unless the instrument is of lab quality.


73,
Don W3FPR

On 11/30/2018 11:12 AM, Charlie T wrote:

Yep,  ur right Don.  A freebie Harbor Freight digital voltmeter appears to
have a helluva lot better accuracy than reality.
Digital calculators on the other hand, ARE accurate.
This changes our mind-set, simply because we see all those digits past the
decimal point on a dVOM.

it was better when we only had slide-rules to calculate things.
Accuracy to more than three places was at best, a guess.
Besides, what good does it do to arrive at a required by-pass capacitor's
value of 0.0110987 µF ?

73, Charlie k3ICH




-Original Message-
From: elecraft-boun...@mailman.qth.net  On
Behalf Of Don Wilhelm
Sent: Friday, November 30, 2018 9:56 AM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] [K3] SWR - Numerical Indication

Petr and all,

Those digital instruments that show 2, 3, or 4 decimal places have given us
a false sense of accuracy.
For instance an instrument that is accurate to 5% and has a 4 digit display
can show us (when measuring a 5 volt source) anywhere between
4.750 volts and 5.250 volts and still be within the 5% accuracy window for
the instrument.

Review the specs and calibration for whatever meter you are using and do not
expect those extra digits to be correct - in other words round the numbers
displayed.

Many wattmeters are only accurate to 20% of the reading - so if one
wattmeter at 100 watts shows 120 watts and another shows 80 watts, the
actual power could be 100 watts.  Take that into consideration.

The Telepost LP-100 when calibrated to NIST standards is accurate to 5% (it
can be lower, but Larry will not guarantee it).  So any power it displays
between 95 and 105 watts can actually be 100 watts.

In other words, look at the specified accuracy of whatever meter you are
using and take that into consideration.  Those extra digits on your meter
may be meaningless.

73,
Don W3FPR


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Re: [Elecraft] [K3] SWR - Numerical Indication

[Charlie T]

Yep,  ur right Don.  A freebie Harbor Freight digital voltmeter appears to
have a helluva lot better accuracy than reality.
Digital calculators on the other hand, ARE accurate.
This changes our mind-set, simply because we see all those digits past the
decimal point on a dVOM.

it was better when we only had slide-rules to calculate things.
Accuracy to more than three places was at best, a guess.
Besides, what good does it do to arrive at a required by-pass capacitor's
value of 0.0110987 µF ?

73, Charlie k3ICH




-Original Message-
From: elecraft-boun...@mailman.qth.net  On
Behalf Of Don Wilhelm
Sent: Friday, November 30, 2018 9:56 AM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] [K3] SWR - Numerical Indication

Petr and all,

Those digital instruments that show 2, 3, or 4 decimal places have given us
a false sense of accuracy.
For instance an instrument that is accurate to 5% and has a 4 digit display
can show us (when measuring a 5 volt source) anywhere between
4.750 volts and 5.250 volts and still be within the 5% accuracy window for
the instrument.

Review the specs and calibration for whatever meter you are using and do not
expect those extra digits to be correct - in other words round the numbers
displayed.

Many wattmeters are only accurate to 20% of the reading - so if one
wattmeter at 100 watts shows 120 watts and another shows 80 watts, the
actual power could be 100 watts.  Take that into consideration.

The Telepost LP-100 when calibrated to NIST standards is accurate to 5% (it
can be lower, but Larry will not guarantee it).  So any power it displays
between 95 and 105 watts can actually be 100 watts.

In other words, look at the specified accuracy of whatever meter you are
using and take that into consideration.  Those extra digits on your meter
may be meaningless.

73,
Don W3FPR


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Re: [Elecraft] [K3] SWR - Numerical Indication

[Petr Ourednik]

So soryy, my fault...
73 - Petr, OK1RP

> Sent from my iPad
> 
> > On Nov 30, 2018, at 6:29 AM, Petr, OK1RP/M0SIS  wrote:
> > 
> > Hi Wes,
> > 
> > excellent! 
> > 
> > Many thanks for this post which is nicely explaining what is going on about
> > the measurement in K3s. 
> > 
> > In fact until now no one talked about the calibrations, uncertainties,
> > errors, accuracy, reading errors, uncertainties A, B and combined
> > uncertainties etc. In that case there is several error sources and factors
> > which need to be calculated in order to get some more precise values ...and
> > in all cases the uncertainties must be calculated together with measured
> > value if we would like to talk about scientific or sophisticated
> > measurement.
> > 
> > Thanks for nice explanation Wes to all.
> > 
> > Best regards.


In reply to this post by Bob McGraw - K4TAX 

I would be surprised if two garden variety instruments, even placed at the same 
point, would agree. The directional bridges/couplers in most "(V)SWR" meters 
that hams routinely use externally or which are built into our radios are not 
precision instruments.  There are a number of error sources in reflection 
measurements; source match, diode non-linearity, coupler tracking errors and 
often the most significant, directivity error. 

In an ideal coupler, (i.e signal separation device) one port measures the 
forward (incident signal) and another measures the reverse (reflected) signal 
and there is no coupling between ports in the unwanted direction(s).  In other 
words there is no signal at the reverse port due to the forward signal.  In a 
real world coupler there is some leakage signal appearing at the reverse port 
due to the forward signal, absent any reflected signal.  The "goodness" of a 
directional coupler in this instance is called "directivity" and the error 
signal is directivity error. Directivity is usually specified in dB.  Really 
good couplers might have directivities in the 40 dB neighborhood.  Really 
really 
good directional bridges can be 50 dB, but so-so units might be 25-30 dB.  Not 
ready for prime time units are lower than this. 

Now I have no way of knowing what the directivities are of the couplers built 
into K3s, KPA500s, KAT500s, etc. but considering that they have to work over 
about 5 octaves, I'm going out on a limb and saying that 25 to 30 dB is a fair 
estimate.  If I'm wrong, I'm sure I'll hear about it.  For sake of discussion 
I'm going to use 26.5 dB.  What this means is that if I terminate the output 
spigot of one of these radios with a perfect 50+j0 load, I'm going to measure a 
leakage signal (directivity error) that is 26.5 dB below the incident value.  
I'll introduce the concept of return loss here. 

We hams usually speak in terms of SWR.  SWR = (1 + p) / (1 - p) where p is the 
reflection coefficient. Here the p = the voltage measured at the reflected port 
and the constant 1 represents the incident signal.  In reality both of these 
quantities are complex numbers, they have both magnitude and phase but SWR 
measurements are scalar, we throw away the phase (since it's difficult to 
measure) and just use the magnitude. (In fact the symbol "p", which is really 
the Greek letter rho, indicates the magnitude of the reflection coefficient in 
normal usage)  We can also express this ratio as return loss, which is -20 * 
log10(p).  So return loss, SWR and reflection coefficient are just different 
ways to express the same thing; the ratio of incident to reflected signal. 

Let's return to our example; the coupler with 26.5 dB directivity, which 
indicates a return loss (RL) of 26.5 dB even with a perfect termination.  Doing 
the math and converting RL = 26.5 dB to SWR we get 1.1:1.  Our perfect load 
measures 1.1:1 with our imperfect instrument.  And this assumes that there are 
no other errors, which there always are. But it gets worse. 

Let's say that the load we want to measure really is 1.1:1.  We now have two 
(apparent) reflections, 1) the real one and 2) the directivity error and they 
both have the same magnitude.  In our simple detector, they sum together.  Now 
I 
said earlier that we don't measure phase, only magnitude, but just because we 
don't, or can't measure the relative phases doesn't mean they aren't there. We 
will examine two cases to determine the limits of error.  Case 1) both 
reflections are in phase, they add up to p + p or 2p, RL = 20.5 and SWR 
~1.21:1.  Case 2) they are exactly out of phase, they sum to zero.  p = 0, RL 
is 
infinite and SWR = 1:1.  The possible RL error is then -6 to +infinity dB! 

In other words, an actual SWR of 1.1:1 can be measured anywhere between 1.0:1 
and 1.2:1.  Is it any wonder that we often read about concerns that one device 
measures one thing, while another located at the same, or close location 
measures something different.  Of course all of this is predicated on a 
directional coupler with 26.5 dB directivity and no other error sources.  It's 

Re: [Elecraft] [K3] SWR - Numerical Indication

[W2xj]

I wish I could find the original post that started this discussion. Very 
frustrating when there is no quoted material. 

Sent from my iPad

> On Nov 30, 2018, at 6:29 AM, Petr, OK1RP/M0SIS  wrote:
> 
> Hi Wes,
> 
> excellent! 
> 
> Many thanks for this post which is nicely explaining what is going on about
> the measurement in K3s. 
> 
> In fact until now no one talked about the calibrations, uncertainties,
> errors, accuracy, reading errors, uncertainties A, B and combined
> uncertainties etc. In that case there is several error sources and factors
> which need to be calculated in order to get some more precise values ...and
> in all cases the uncertainties must be calculated together with measured
> value if we would like to talk about scientific or sophisticated
> measurement.
> 
> Thanks for nice explanation Wes to all.
> 
> Best regards.
> 
> 
> 
> -
> 73 - Petr, OK1RP 
> "Apple & Elecraft freak" 
> B:http://ok1rp.blogspot.com
> G+:http://goo.gl/w3u2s9
> G+: http://goo.gl/gP99xq
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
> __
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> Message delivered to w...@w2xj.net
> 

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Re: [Elecraft] [K3] SWR - Numerical Indication

[Don Wilhelm]

Petr and all,

Those digital instruments that show 2, 3, or 4 decimal places have given 
us a false sense of accuracy.
For instance an instrument that is accurate to 5% and has a 4 digit 
display can show us (when measuring a 5 volt source) anywhere between 
4.750 volts and 5.250 volts and still be within the 5% accuracy window 
for the instrument.


Review the specs and calibration for whatever meter you are using and do 
not expect those extra digits to be correct - in other words round the 
numbers displayed.


Many wattmeters are only accurate to 20% of the reading - so if one 
wattmeter at 100 watts shows 120 watts and another shows 80 watts, the 
actual power could be 100 watts.  Take that into consideration.


The Telepost LP-100 when calibrated to NIST standards is accurate to 5% 
(it can be lower, but Larry will not guarantee it).  So any power it 
displays between 95 and 105 watts can actually be 100 watts.


In other words, look at the specified accuracy of whatever meter you are 
using and take that into consideration.  Those extra digits on your 
meter may be meaningless.


73,
Don W3FPR

On 11/30/2018 9:29 AM, Petr, OK1RP/M0SIS wrote:

Hi Wes,

excellent!

Many thanks for this post which is nicely explaining what is going on about
the measurement in K3s.

In fact until now no one talked about the calibrations, uncertainties,
errors, accuracy, reading errors, uncertainties A, B and combined
uncertainties etc. In that case there is several error sources and factors
which need to be calculated in order to get some more precise values ...and
in all cases the uncertainties must be calculated together with measured
value if we would like to talk about scientific or sophisticated
measurement.

Thanks for nice explanation Wes to all.

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Re: [Elecraft] [K3] SWR - Numerical Indication

[Petr, OK1RP/M0SIS]

Hi Wes,

excellent! 

Many thanks for this post which is nicely explaining what is going on about
the measurement in K3s. 

In fact until now no one talked about the calibrations, uncertainties,
errors, accuracy, reading errors, uncertainties A, B and combined
uncertainties etc. In that case there is several error sources and factors
which need to be calculated in order to get some more precise values ...and
in all cases the uncertainties must be calculated together with measured
value if we would like to talk about scientific or sophisticated
measurement.

Thanks for nice explanation Wes to all.

Best regards.



-
73 - Petr, OK1RP 
"Apple & Elecraft freak" 
B:http://ok1rp.blogspot.com
G+:http://goo.gl/w3u2s9
G+: http://goo.gl/gP99xq
--
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Re: [Elecraft] [K3] SWR - Numerical Indication

[Wes Stewart]

I would be surprised if two garden variety instruments, even placed at the same 
point, would agree. The directional bridges/couplers in most "(V)SWR" meters 
that hams routinely use externally or which are built into our radios are not 
precision instruments.  There are a number of error sources in reflection 
measurements; source match, diode non-linearity, coupler tracking errors and 
often the most significant, directivity error.


In an ideal coupler, (i.e signal separation device) one port measures the 
forward (incident signal) and another measures the reverse (reflected) signal 
and there is no coupling between ports in the unwanted direction(s).  In other 
words there is no signal at the reverse port due to the forward signal.  In a 
real world coupler there is some leakage signal appearing at the reverse port 
due to the forward signal, absent any reflected signal.  The "goodness" of a 
directional coupler in this instance is called "directivity" and the error 
signal is directivity error. Directivity is usually specified in dB.  Really 
good couplers might have directivities in the 40 dB neighborhood.  Really really 
good directional bridges can be 50 dB, but so-so units might be 25-30 dB.  Not 
ready for prime time units are lower than this.


Now I have no way of knowing what the directivities are of the couplers built 
into K3s, KPA500s, KAT500s, etc. but considering that they have to work over 
about 5 octaves, I'm going out on a limb and saying that 25 to 30 dB is a fair 
estimate.  If I'm wrong, I'm sure I'll hear about it.  For sake of discussion 
I'm going to use 26.5 dB.  What this means is that if I terminate the output 
spigot of one of these radios with a perfect 50+j0 load, I'm going to measure a 
leakage signal (directivity error) that is 26.5 dB below the incident value.  
I'll introduce the concept of return loss here.


We hams usually speak in terms of SWR.  SWR = (1 + p) / (1 - p) where p is the 
reflection coefficient. Here the p = the voltage measured at the reflected port 
and the constant 1 represents the incident signal.  In reality both of these 
quantities are complex numbers, they have both magnitude and phase but SWR 
measurements are scalar, we throw away the phase (since it's difficult to 
measure) and just use the magnitude. (In fact the symbol "p", which is really 
the Greek letter rho, indicates the magnitude of the reflection coefficient in 
normal usage)  We can also express this ratio as return loss, which is -20 * 
log10(p).  So return loss, SWR and reflection coefficient are just different 
ways to express the same thing; the ratio of incident to reflected signal.


Let's return to our example; the coupler with 26.5 dB directivity, which 
indicates a return loss (RL) of 26.5 dB even with a perfect termination.  Doing 
the math and converting RL = 26.5 dB to SWR we get 1.1:1.  Our perfect load 
measures 1.1:1 with our imperfect instrument.  And this assumes that there are 
no other errors, which there always are. But it gets worse.


Let's say that the load we want to measure really is 1.1:1.  We now have two 
(apparent) reflections, 1) the real one and 2) the directivity error and they 
both have the same magnitude.  In our simple detector, they sum together.  Now I 
said earlier that we don't measure phase, only magnitude, but just because we 
don't, or can't measure the relative phases doesn't mean they aren't there. We 
will examine two cases to determine the limits of error.  Case 1) both 
reflections are in phase, they add up to p + p or 2p, RL = 20.5 and SWR 
~1.21:1.  Case 2) they are exactly out of phase, they sum to zero.  p = 0, RL is 
infinite and SWR = 1:1.  The possible RL error is then -6 to +infinity dB!


In other words, an actual SWR of 1.1:1 can be measured anywhere between 1.0:1 
and 1.2:1.  Is it any wonder that we often read about concerns that one device 
measures one thing, while another located at the same, or close location 
measures something different.  Of course all of this is predicated on a 
directional coupler with 26.5 dB directivity and no other error sources.  It's 
entirely possible that the Elecraft couplers are better than this.  They are 
certainly no better than 40 dB since the internal reference resistors are 51 
instead of 50 ohm.  Plus the "Tandem Match" configuration is in itself not a 
great match to the transmitter output.(1)  Furthermore, the coupler, at least in 
a K3 is driven by a LPF, which isn't a great 50 ohm source. Plus the coupler 
output port isn't connected directly to the coax connector. and so on and so 
forth (2).  All of this creates "uncertainty."


In a metrology lab heroic efforts are made to reduce uncertainty but do we, or 
should we, really care in this situation?  In my opinion, no, but everyone is 
free to differ.


Wes  N7WS

(1)  See "An HF In-Line Return Loss And Power Meter" by Paul Kiciak, N2PK.  
http://n2pk.com/#TP3


(2)  See "Gauge the Accuracy of SNA Measurements" 

Re: [Elecraft] [K3] SWR - Numerical Indication

[Mel Farrer via Elecraft]

Dick, 
While Bob is correct, the bottom line is not SWR but the R and j numbers.  
There are numerous values that will give you a 1.1:1, but only 50+j0 will be 
the true match of 1.0:1.  So,unless you do not have the equipment to measure 
the polar values, be thankful you have 1.1:1.  
Mel, K6KBE

  From: Bob McGraw K4TAX 
 To: elecraft@mailman.qth.net 
 Sent: Friday, July 27, 2018 1:10 PM
 Subject: Re: [Elecraft] [K3] SWR - Numerical Indication
   
Yes, the K3S SWR display can show a 1.0:1 value.  But in my case,  it 
does not exactly agree with another instrument in the feed line system. 
     As to why you are showing two different values, as minute as they 
are I might add, you are measuring 2 different places in the feed line. 
   In my thinking, it is physically impossible to put two  SWR bridges 
in the same place electrically.

In theory the SWR on a given line should be the same at all places, but 
maybe not since there is loss of some minute value in the line.      
Since you are measuring on antennas, common mode current, may be the 
contributing cause.  Difference in measurement calibration, may be a 
factor as well.

VSWR bridges are calibrated with some specific value of load. Ideally, 
it is 50 ohm non-reactive, but it could be 49 ohms or 51 ohms or some 
other value.   Just because a load says "50 ohms" on the label is no 
real indication that is actually fact.    To that end, I have 3 dummy 
loads which are "50 ohm" loads according to the label but none are not 
true 50 ohm loads.    I do have a Celwave load that says 50.5 ohms on 
the label and measures 50.5 ohms per my General Radio bridge.    The 
others are +/- something, but good enough to evaluate a ham transmitter 
or amplifier.

Frankly, a difference between 1.1:1 and 1.0:1 won't make any realistic 
difference in any form or fashion other than to appease the operator.

73

Bob, K4TAX



On 7/27/2018 9:58 AM, Dick Dickinson wrote:
> I've noticed that I'm not showing a reading of less than 1.1:1 SWR on my
> antennas per K3 SWR Numerical Readout.  K3EZ will record 1.0:1 SWR in band
> sweeps.
>
> Can the K3(S) Numerical Display show 1.0:1 SWR?  If so, is there a likely
> reason why K3EZ will show 1.0:1 while my K3 will only go as far down as
> 1.1:1?
>
>
> Dick -  KA5KKT
>
>
>
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Re: [Elecraft] [K3] SWR - Numerical Indication

[Bob McGraw K4TAX]

Yes, the K3S SWR display can show a 1.0:1 value.  But in my case,  it 
does not exactly agree with another instrument in the feed line system. 
    As to why you are showing two different values, as minute as they 
are I might add, you are measuring 2 different places in the feed line. 
  In my thinking, it is physically impossible to put two  SWR bridges 
in the same place electrically.


In theory the SWR on a given line should be the same at all places, but 
maybe not since there is loss of some minute value in the line.      
Since you are measuring on antennas, common mode current, may be the 
contributing cause.  Difference in measurement calibration, may be a 
factor as well.


VSWR bridges are calibrated with some specific value of load. Ideally, 
it is 50 ohm non-reactive, but it could be 49 ohms or 51 ohms or some 
other value.   Just because a load says "50 ohms" on the label is no 
real indication that is actually fact.    To that end, I have 3 dummy 
loads which are "50 ohm" loads according to the label but none are not 
true 50 ohm loads.    I do have a Celwave load that says 50.5 ohms on 
the label and measures 50.5 ohms per my General Radio bridge.    The 
others are +/- something, but good enough to evaluate a ham transmitter 
or amplifier.


Frankly, a difference between 1.1:1 and 1.0:1 won't make any realistic 
difference in any form or fashion other than to appease the operator.


73

Bob, K4TAX



On 7/27/2018 9:58 AM, Dick Dickinson wrote:

I've noticed that I'm not showing a reading of less than 1.1:1 SWR on my
antennas per K3 SWR Numerical Readout.  K3EZ will record 1.0:1 SWR in band
sweeps.

Can the K3(S) Numerical Display show 1.0:1 SWR?  If so, is there a likely
reason why K3EZ will show 1.0:1 while my K3 will only go as far down as
1.1:1?


Dick -  KA5KKT



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Re: [Elecraft] [K3] SWR - Numerical Indication

[ab2tc]

Hi again,

Oops I accidentally sent the message without the context quote.

Get a good dummy load and you will get the indication "1.0 - 1". I have both
the K3 (souped up to near K3S) and the K3S and they both do it. You are not
confusing this with with 1.1, are you? 

AB2TC - Knut 


Dick Dickinson wrote
> I've noticed that I'm not showing a reading of less than 1.1:1 SWR on my
> antennas per K3 SWR Numerical Readout.  K3EZ will record 1.0:1 SWR in band
> sweeps.
> 
> Can the K3(S) Numerical Display show 1.0:1 SWR?  If so, is there a likely
> reason why K3EZ will show 1.0:1 while my K3 will only go as far down as
> 1.1:1?
> 
> 
> Dick -  KA5KKT
> 
> 





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Re: [Elecraft] [K3] SWR - Numerical Indication

[ab2tc]

Hi,

Get a good dummy load and you will get the indication "1.0 - 1". I have both
the K3 (souped up to near K3S) and the K3S and they both do it. You are not
confusing this with with 1.1, are you?

AB2TC - Knut





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[Elecraft] [K3] SWR - Numerical Indication

[Dick Dickinson]

I've noticed that I'm not showing a reading of less than 1.1:1 SWR on my
antennas per K3 SWR Numerical Readout.  K3EZ will record 1.0:1 SWR in band
sweeps.

Can the K3(S) Numerical Display show 1.0:1 SWR?  If so, is there a likely
reason why K3EZ will show 1.0:1 while my K3 will only go as far down as
1.1:1?


Dick -  KA5KKT



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Re: [Elecraft] K3 SWR/Tuner Utility

[Jim McDonald]

My computer is running the pre-anniversary edition of Windows 10 Professional.

 

I just started K3_EZ V2.0.0.8, and it works fine.  I forget features of that 
version seemed to have bugs, but I also have an older edition installed as 
well.  It may have a problem saving TX/RX EQ settings, but I'm not sure.

 

I always liked the program, which was developed by N2BC.  It hasn’t been 
updated for a long time.

 

For those not familiar with it, here’s a summary of the features from the help 
file:

 

Overview:  K3EZ is designed to provide the following basic functions:

*A simple frequency ‘Stacking’ function with most of the K3 front panel 
buttons available to ‘click and change’

*An easy to use frequency memory database

*An easy to use graphic display and Set and Get of RX and TX Equalizers 
with a saved setting database

*Basic K3 information (COM port, Firmware levels, installed options, 
filters, etc.)

*A formatted and functionally organized display of the majority of the K3 
CONFIG settings

*An easy to use K3 Command Utility, formats K3 responses in ASCII or HEX

*SWR Scan function to sample and graph SWR

With the exception of the K3 RX and TX equalizers, the program DOES NOT change 
K3 CONFIG settings.  It does provide easy to use access to the settings, but 
YOU make the changes!

 

73, Jim N7US

 

 

-Original Message-



 

Has anyone gotten K3 EZ to run under Windows 10?  It worked fine for me under 
Windows 7 but no luck on Windows 10.  Thanks.

 

NWØM  Mitch

 

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Re: [Elecraft] K3 SWR/Tuner Utility

[NW0M]

Has anyone gotten K3 EZ to run under Windows 10?  It worked fine for me under
Windows 7 but no luck on Windows 10.  Thanks.

NWØM  Mitch



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[Elecraft] K3 SWR/Tuner Utility

[Doug Ellmore]

Thanks to Barry K3NDM, I found a nice K3 utility to scan swr of a band and
then do a KAT3 setup (tuner setup) so you can have instant tuned stacks on
each band.

http://www.na6m.com/EZ-K3/K3_EZ_V2008.zip

The first time I used it to tune my Inverted L for 160m, it yielded the
following results.

SWR:|

4.0
+


|

3.8
+


|

3.6
+


|

3.4
+


|

3.2
+


|

3.0
+


|

2.8
+


|

2.6
+


|

2.4
+


|

2.2
+


|

2.0
+


|

1.8
+


|

1.6
+


|

1.4 +
*

|   *   *
*
1.2 +   *   *   *   *   *   *   *   *
*   *
|   *   *
*   *
1.0 +   *
*   *

|---|---+---+---+---+---|---+---+---+---+---|---+---+---+---+---|---+---+---+---+---|
MHz:   1.801.851.90
1.952.00

10/12/2016 9:04:25 PM NOTES:

Frequency SWR
- ---
00180 1.4
00181 1.3
00182 1.3
00183 1.2
00184 1.2
00185 1.1
00186 1.2
00187 1.2
00188 1.2
00189 1.2
00190 1.3
00191 1.2
00192 1.2
00193 1.1
00194 1.1
00195 1.2
00196 1.0
00197 1.0
00198 1.2
00199 1.1
00200 1.0





-- 
Doug NA1DX
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[Elecraft] K3 SWR Panel Reading 1.2 - 1.

[Bob Myers]

K3 SWR Panel Reading is 1.2 - 1.

I’ve recently completed K3 S/N 8156. It’s a basic K3, 10-watt unit with the 
only option being a 250 Hz CW filter. (Of course it has the 2.7 kHz filter 
installed.) No other options. 

The K3 Panel SWR indicates 1.2 - 1 during transmit when the actual SWR is 
probably 1.0 - 1.  The 1.2 - 1 shows with a 50-ohm dummy load connected 
directly to the antenna jack of the K3 or with an antenna using a Johnson 
Matchbox adjusted to 1 - 1 using an LP-100 digital wattmeter. The dummy load 
when attached directly to a different modern transceiver at the antenna jack 
shows 1.0 - 1.

If I mistune the Johnson Matchbox, the K3 SWR indication does go up but no 
matter how I tune the Matchbox, the K3 never shows below 1.2 - 1. The Matchbox 
attached to the other modern transceiver shows 1 - 1.

I don’t see an adjustment for the K3 SWR minimum setting in a menu. And I do 
not see anything mentioned in the K3 Operating Manual or the KE7X Extended 
Manual.

Any suggestions?

Thanks,

Bob W1XT
Sun City West, AZ
K1, KX1 K2 1434, K2 5843, K3 and other units.

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[Elecraft] [K3] SWR meter unstable

[Eduardo González]

Hello friends.
I have a small issue with SWR meter.
If SWR  1.5 aprox reading of SWR meter show erratic spikes over 3
while i'm talking or doing a tone. Spikes aren't proportional respect
to voice intensity. I have tested using dummy load and tuned antennas,
including dummy load with another impedance (100 ohm for example) so i
can get SWR  1.5 readings. This problem is old, started few months
after purchase the equipment. Would be a RF loop back issue?. Has
anyone had the same problem? Setup is K3/100 with ATU. Problem is
present with or without ATU enabled

Edu YY4GMJ
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[Elecraft] K3 SWR S meter not functioning

[Gary Smith]

I am working the Stew Perry test and noticed my indicator for SWR  S 
meter stopped not working and that is the same on all bands. If I 
adjust the RF control I can see the level indicated but there is no 
sign of Rf life. I turned off the radio  back on but this persists. 
Is there something I may have bumped to have stopped the display from 
indicating any values?

Thanks

Gary
KA1J


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Re: [Elecraft] K3 SWR S meter not functioning

[Chuck Shefflette - AA3CS]

Sounds like you may have turned off the AGC - assuming you are hearing signals 
but just seeing no meter movement.

73, Chuck AA3CS

Sent from my iPad

On Dec 30, 2012, at 7:11, Gary Smith g...@ka1j.com wrote:

 I am working the Stew Perry test and noticed my indicator for SWR  S 
 meter stopped not working and that is the same on all bands. If I 
 adjust the RF control I can see the level indicated but there is no 
 sign of Rf life. I turned off the radio  back on but this persists. 
 Is there something I may have bumped to have stopped the display from 
 indicating any values?
 
 Thanks
 
 Gary
 KA1J
 
 
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Re: [Elecraft] K3 SWR

[briana]

Jay,

The K3 protects itself against too high SWR's by cutting back power.
An SWR of 1.8:1 is quite acceptable.

As to why the SWR is 1.8 , there could be many reasons.
1) Antenna too long or too short.  Run an SWR curve vs frequency to see 
which.
2) Antenna height.  Depending upon height the impedance of the antenna 
can be very low at low heights and as much as ~100 ohms at some heights.

From the antenna handbook for a half wave dipole for 20 M:
Height in wavelengths Feedpoint Impedance
.1 (~7 feet)   20 ohms  (SWR =2.5)
.17(~11 feet)  50 (SWR = 1)
.34 (~22 feet)98 (SWR =2)
beyond this point the impedance decreases and oscillates about a value 
of 72 ohms (SWR =1.44)
3) With any feedpoint impedance other than 50 ohms, the SWR seen at the 
shack end of the coax is highly dependent on coax length.


If you bought the coax new, the last thing to consider is the coax 
itself - provided it hasn't been abused or is very old.


It is common practice to trim the length of the antenna at a given 
height to attempt to adjust the SWR favorably.


73 de Brian/K3KO

On 12/9/2012 2:16 AM, Jay Krishna wrote:

Just completed assembling my new K3/100; I am completely new to this rig, and 
just getting used to it. In initial transmitter power calibration into a dummy 
load, I saw an SWR of ~1:1. However, into my 20M mono-band dipole, I see it is 
~1.8:1. I am wondering if anybody can help answer these questions:

1. Is it safe to operate the K3 with an SWR as high as 1.8:1 (just eager to 
test the new K3 on the air)?
2. Do I need to check if there is a problem with my dipole antenna (wet coax, 
etc.)?

Thanks,

Jay (KD6AMA)
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-
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2012.0.2221 / Virus Database: 2634/5446 - Release Date: 12/08/12


   


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Re: [Elecraft] K3 SWR

[Vic K2VCO]

It is perfectly safe.

The K3 cuts back power when it sees the equivalent reflected power of a 2:1 SWR at 100 
watts. So it will operate normally at a 1.8:1 SWR. If the LOWEST SWR is 1.8:1, then it 
probably exceeds 2:1 somewhere in the band, where you will not be able to get a full 100 
watts.


I suggest you check the SWR at various points (an antenna analyzer is helpful, but you can 
just transmit at different frequencies and record the results). Once you find the point of 
lowest SWR, you can determine how much to lengthen or shorten the antenna to move this 
point to the center of the band or your favorite spot.


As another writer said, it is unlikely that you will get a 1:1 SWR from a coax-fed dipole 
under most circumstances. The K3 will be happy as long as it is under 2:1 (and you can 
still operate with reduced power if it is over 2:1).


On 12/8/2012 11:16 PM, Jay Krishna wrote:

Just completed assembling my new K3/100; I am completely new to this rig, and 
just getting used to it. In initial transmitter power calibration into a dummy 
load, I saw an SWR of ~1:1. However, into my 20M mono-band dipole, I see it is 
~1.8:1. I am wondering if anybody can help answer these questions:
  
1. Is it safe to operate the K3 with an SWR as high as 1.8:1 (just eager to test the new K3 on the air)?

2. Do I need to check if there is a problem with my dipole antenna (wet coax, 
etc.)?
  
Thanks,
  
Jay (KD6AMA) 		 	   		

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--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/

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[Elecraft] K3 SWR

[Jay Krishna]

Just completed assembling my new K3/100; I am completely new to this rig, and 
just getting used to it. In initial transmitter power calibration into a dummy 
load, I saw an SWR of ~1:1. However, into my 20M mono-band dipole, I see it is 
~1.8:1. I am wondering if anybody can help answer these questions:
 
1. Is it safe to operate the K3 with an SWR as high as 1.8:1 (just eager to 
test the new K3 on the air)?
2. Do I need to check if there is a problem with my dipole antenna (wet coax, 
etc.)?
 
Thanks,
 
Jay (KD6AMA)  
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[Elecraft] (K3) SWR Consistent - low or high power

[Tom Boucher]

My theory in these cases is that it's nothing to do with bad antenna 
connections, but more due to the rig putting out a higher harmonic content at 
higher power levels. The SWR meter sees a bad SWR at the harmonic frequency so 
the reading is slightly worse.

73
Tom G3OLB

N3OI wrote:
*One observation:* I use low power to set SWR with my TenTec manual tuner.
My FT-920's SWR meter would usually shift a bit when I increased power to
100w and I would then quickly tweak it back down.  With the K3's SWR meter
(no ATU installed), after setting the tuner at 10w or so, the reading stays
the same when power is increased to 100w. 

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Re: [Elecraft] (K3) SWR Consistent - low or high power

[Brian Alsop]

Some of this effect hqs to do with the reflected power diode.
Depening upon the sense circuity, the reflected power diode may not see 
enough voltaqe to be fully conducting.  Thus it reads less current in 
the reflected position and hence lower SWR that at higher powers.

Also the type of diode used is important.  I believe the K3 use Schotky 
diodes which conduct at lower voltages than say silicon diodes. 
Germanium diodes are even better but fragile and harder to get these days.

73 DE Brian/K3KO




Tom Boucher wrote:
 My theory in these cases is that it's nothing to do with bad antenna 
 connections, but more due to the rig putting out a higher harmonic content at 
 higher power levels. The SWR meter sees a bad SWR at the harmonic frequency 
 so the reading is slightly worse.
 
 73
 Tom G3OLB
 
 N3OI wrote:
 *One observation:* I use low power to set SWR with my TenTec manual tuner.
 My FT-920's SWR meter would usually shift a bit when I increased power to
 100w and I would then quickly tweak it back down.  With the K3's SWR meter
 (no ATU installed), after setting the tuner at 10w or so, the reading stays
 the same when power is increased to 100w. 
 
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Re: [Elecraft] (K3) SWR Consistent - low or high power

[Vic K2VCO]

There are several causes for varying SWR readings with power level:

1) Poor diode linearity -- diodes are less sensitive at low levels, and 
reflected power 
may be very low at QRP levels. This effect shows as a low indicated SWR at low 
power 
levels, which then becomes more accurate past a given power level.

2) Harmonics -- as described below by G3OLB.

3) Parasitic oscillations -- a misadjusted amplifier can oscillate a few 
hundred kHz from 
the operating frequency, where the antenna is not resonant (or a tuner is not 
tuned). VHF 
parastics are also possible. Any significant off-frequency output can cause a 
high SWR 
reading. Needless to say, this is very serious and must be corrected.

4) Common-mode current -- antenna currents on the outside of a coax feedline, 
caused by 
feeding a dipole (etc.) without a balun, or by coax running parallel to antenna 
wires even 
with a balun, can upset SWR readings. This effect changes with the feedline 
length as well 
as the power. SWR indicators may vary in their susceptibility to this effect.

On 10/10/2012 2:20 AM, Tom Boucher wrote:
 My theory in these cases is that it's nothing to do with bad antenna 
 connections, but
 more due to the rig putting out a higher harmonic content at higher power 
 levels. The
 SWR meter sees a bad SWR at the harmonic frequency so the reading is slightly 
 worse.

 73 Tom G3OLB

 N3OI wrote: *One observation:* I use low power to set SWR with my TenTec 
 manual
 tuner. My FT-920's SWR meter would usually shift a bit when I increased power 
 to 100w
 and I would then quickly tweak it back down.  With the K3's SWR meter (no ATU
 installed), after setting the tuner at 10w or so, the reading stays the same 
 when power
 is increased to 100w.


-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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Re: [Elecraft] (K3) SWR Consistent - low or high power

[Randy Farmer]

It's pretty unlikely you'd see harmonic content on any kind of broadband 
power sensor like a SWR meter. Even if the transmitter was really bad 
and had harmonic levels only 40 dB down, this would mean for 100 Watts 
output you would be getting 10 mW in harmonic energy, which wouldn't 
wiggle anybody's meter very much. And if the total harmonic power at 40 
dB down was just equal to the reflected power from your antenna 
mismatch, this would mean the antenna would have a VSWR of 1.07. My 
money's on diode nonlinearities at low power levels.

73...
Randy, W8FN

On 10/10/2012 04:20, Tom Boucher wrote:
 My theory in these cases is that it's nothing to do with bad antenna 
 connections, but more due to the rig putting out a higher harmonic content at 
 higher power levels. The SWR meter sees a bad SWR at the harmonic frequency 
 so the reading is slightly worse.

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Re: [Elecraft] (K3) SWR Consistent - low or high power

[Don Wilhelm]

Randy,

What you say is true only if working into a load that is not frequency 
selective - like a dummy load.
If working into an antenna, that will be frequency selective and any 
harmonics will increase the SWR indication.

73,
Don W3FPR

On 10/10/2012 8:17 PM, Randy Farmer wrote:
 It's pretty unlikely you'd see harmonic content on any kind of broadband
 power sensor like a SWR meter. Even if the transmitter was really bad
 and had harmonic levels only 40 dB down, this would mean for 100 Watts
 output you would be getting 10 mW in harmonic energy, which wouldn't
 wiggle anybody's meter very much. And if the total harmonic power at 40
 dB down was just equal to the reflected power from your antenna
 mismatch, this would mean the antenna would have a VSWR of 1.07. My
 money's on diode nonlinearities at low power levels.



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Re: [Elecraft] (K3) SWR Consistent - low or high power

[riese-k3djc]

WOW  

Bob K3DJC


On Wed, 10 Oct 2012 20:32:58 -0400 Don Wilhelm w3...@embarqmail.com
writes:
 Randy,
 
 What you say is true only if working into a load that is not 
 frequency 
 selective - like a dummy load.
 If working into an antenna, that will be frequency selective and any 
 
 harmonics will increase the SWR indication.
 
 73,
 Don W3FPR
 
 On 10/10/2012 8:17 PM, Randy Farmer wrote:
  It's pretty unlikely you'd see harmonic content on any kind of 
 broadband
  power sensor like a SWR meter. Even if the transmitter was really 
 bad
  and had harmonic levels only 40 dB down, this would mean for 100 
 Watts
  output you would be getting 10 mW in harmonic energy, which 
 wouldn't
  wiggle anybody's meter very much. And if the total harmonic power 
 at 40
  dB down was just equal to the reflected power from your antenna
  mismatch, this would mean the antenna would have a VSWR of 1.07. 
 My
  money's on diode nonlinearities at low power levels.
 
 
 
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Re: [Elecraft] (K3) SWR Consistent - low or high power

[Randy Farmer]

My example assumes a worst case of 0 dB return loss at all harmonic 
frequencies (i.e., the harmonic energy is all reflected). Any radiation 
or other loss mechanism at the harmonic frequencies will just decrease 
their reflected power and lessen their contribution to the total 
broadband reflected power seen by the meter. The real situation is even 
more complicated, as the directivity of the wattmeter coupler as a 
function of frequency must also be taken into account to determine the 
actual indicated VSWR.

Also, I should have said in the original post ... your antenna would 
have a VSWR of 1.07 AT THE FUNDAMENTAL FREQUENCY.

73...
Randy, W8FN

On 10/10/2012 19:32, Don Wilhelm wrote:
 Randy,

 What you say is true only if working into a load that is not frequency 
 selective - like a dummy load.
 If working into an antenna, that will be frequency selective and any 
 harmonics will increase the SWR indication.

 73,
 Don W3FPR

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[Elecraft] K3 SWR Consistent - Low or High Power

[N4OI - Ken]

Well, my K3/100 and P3 are now a whole week old!  Had a great time assembling
and now having a blast getting to know them -- the P3 and the CW autospot
and APF features are favorites so far.  

*One observation:* I use low power to set SWR with my TenTec manual tuner.
My FT-920's SWR meter would usually shift a bit when I increased power to
100w and I would then quickly tweak it back down.  With the K3's SWR meter
(no ATU installed), after setting the tuner at 10w or so, the reading stays
the same when power is increased to 100w. 

I assume there is a difference in the K3's SWR sensing circuit that makes it
more consistent regardless of power out, but just wanted to see if this
observation makes sense.Thanks in advance!

73 ES GOD BLESS U ES URS DE KEN N4OI 



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[Elecraft] K3: SWR meter readings on 10m...

[VK7JB]

Hello All,

I've just noticed that the SWR meter on my K3 is reading higher than
expected on 10m.

I have 2 different 50 ohm dummy loads. Both have 1.1:1 as measured by my
external LP-100A meter and  my MFJ 259b AA.  

If I connect either dummy load directly into the ANT1 connector of the K3
(no connector lead at all or a very short lead between the DL and the K3
ANT1) and read SWR on 10m, it is measured by the K3 as 1.5:1.   On 15m, SWR
reads 1.4:1 but on 20m and lower bands, the SWR displayed by the K3 accords
with the LP-100A external meter (1.1:1).

Is this frequency-related phenomenon common to all K3's, or just mine?  Is
any adjustment possible or am I sweating over nothing.  Perhaps this SWR
difference is within spec @ 28MHz??


73,

John
VK7JB

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Re: [Elecraft] K3: SWR meter readings on 10m..mystery solved...

[VK7JB]

I've solved my mystery.

I read in the archives that the KAT3 ATU is not completely out of circuit in
bypass mode.  If I understand correctly, small values of L and C are used
to remove it functionally, but there is stray reactance that might
contribute to the higher indicated SWR on some bands.

So then I wondered if the KAT3 might need to be tuned at least once into a
50 ohm load for the bypass state to be correctly determined.  Made sense
in my imagination, and thinking on it,  I realised I'd never tuned the ATU
into a 50 ohm load before.

So I did that - tuned the KAT3 to the dummy load on the bands where it
previously indicated higher than expected in ATU bypass mode.  I let it do
its stuff and find a match for the dummy load, then bypassed the ATU.  

Now, in ATU Bypass mode, the K3 reads 1.0:1 SWR into the same dummy load
that it previously showed as 1.5:1.   Issue gone.

73,
John
VK7JB



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Re: [Elecraft] K3: SWR meter readings on 10m..mystery solved...

[Dave Perry]

John,

I noticed the same high SWR in bypass mode on 10M the other day.  I have the 
KPA500 and thus was wondering why the K3 was seeing up to a 1.7 to 1 SWR 
into the KPA500.  So I got home from work today and tried your solution.  I 
turned on the ATU and tuned into a 50 ohm dummy load.  When I went back to 
normal operation in Bypass mode, the SWR into the amp was back to 1.1 to 1. 
Thanks for the tip.

Dave, N4QS

- Original Message - 
From: VK7JB zen...@netspace.net.au
To: elecraft@mailman.qth.net
Sent: Monday, June 27, 2011 7:39 AM
Subject: Re: [Elecraft] K3: SWR meter readings on 10m..mystery solved...


 I've solved my mystery.

 I read in the archives that the KAT3 ATU is not completely out of circuit 
 in
 bypass mode.  If I understand correctly, small values of L and C are 
 used
 to remove it functionally, but there is stray reactance that might
 contribute to the higher indicated SWR on some bands.

 So then I wondered if the KAT3 might need to be tuned at least once into a
 50 ohm load for the bypass state to be correctly determined.  Made sense
 in my imagination, and thinking on it,  I realised I'd never tuned the ATU
 into a 50 ohm load before.

 So I did that - tuned the KAT3 to the dummy load on the bands where it
 previously indicated higher than expected in ATU bypass mode.  I let it do
 its stuff and find a match for the dummy load, then bypassed the ATU.

 Now, in ATU Bypass mode, the K3 reads 1.0:1 SWR into the same dummy load
 that it previously showed as 1.5:1.   Issue gone.

 73,
 John
 VK7JB



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[Elecraft] K3 SWR Readout Accuracy Question

[Edward R. Cole]

Stan,

It sounds like you assume the 48-inch jumper is OK.  That it first 
think I would swap out to determine if it is affecting your 
readings.  Bad cables sneak up and bite me in the rear way too 
often (because I assume they are good).  Or If you can connect the K2 
thru the same 48-inch cable used with the K3, that will be a better comparison.

If you have a dummy load, directly connect it to the K3 and read the 
SWR.  If you have two dummy loads connect them to the K3 with a 
coaxial tee.  This will present a 25-ohm load  (VSWR=2:1).

If the K3 SWR reads significantly different using the dummy loads 
then you have a problem in the K3.

That being said I never depend on internal SWR meters.  When I want 
to know exactly then its either the Bird43 power meter or directional 
couplers and calculate VSWR from forward and reflected readings.

73, Ed - KL7UW

--

Message: 2
Date: Thu, 31 Mar 2011 12:19:44 -0400 (EDT)
From: stan levandowski sjl...@optonline.net
Subject: [Elecraft] K3 SWR Readout Accuracy Question
To: elecraft@mailman.qth.net
Message-ID:
 4097185.180346.1301588384528.javamail.sjl...@mstr20.srv.hcvlny.cv.net

Content-Type: text/plain; charset=UTF-8; format=flowed; delsp=no

On my newly assembled kit K3/10 without the internal ATU, I've noticed
that the SWR readouts are higher than those on my K2 which agrees with
my analog inline meter.  Into a 50 ohm dummy load all three readings are
1.0:1, but on an actual antenna the readings differ.

For example, where my K2 and  the analog meter read 1.4:1, the K3 says
1.9:1.  this variance increases as the SWR increases and decreases as
the actual SWR decreases, hence the agreement among all three measures
on 1:1 when operating into a dummy load.

All readings taken at 5 watts, same antenna, same  SG-237 autocoupler,
same cable routings, and the internal ATU in the K2 bypassed.  The only
variable is the actual 48coax jumper going from the K3 to the patch
panel.

I just finished the K3 yesterday so I am just a K3 beginner. However I
could find nothing in the manual about SWR calibration.

Any pointers would be appreciated.  Other than this, everything appears
to be working great and the K3 DSP is fabulous.

Stan WB2LQF
K3 #5244



73, Ed - KL7UW, WD2XSH/45
==
BP40IQ   500 KHz - 10-GHz   www.kl7uw.com
EME: 144-1.4kw, 432-100w, 1296-testing*, 3400-winter?
DUBUS Magazine USA Rep dubus...@hotmail.com
==
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Re: [Elecraft] K3 SWR Readout Accuracy Question

[Ron D'Eau Claire]

Even if your cable is good, a change in length will have an effect on the
SWR between two meters (internal to the K3 and your external meter). The
effect will be greater with increasing frequency and increasing SWR. 

Also, the accuracy of typical SWR bridges is best only at 1:1, and decreases
as the SWR rises. Their function is to show a matched condition (1:1) with
reasonable accuracy. 

If you want to see how closely the measurements agree, connect your bridge
to the K3 with a minimum length connector  - directly mount it onto the K3
with an adapter and avoid all cables is best. 

Ron AC7AC

-Original Message-

On my newly assembled kit K3/10 without the internal ATU, I've noticed
that the SWR readouts are higher than those on my K2 which agrees with
my analog inline meter.  Into a 50 ohm dummy load all three readings are
1.0:1, but on an actual antenna the readings differ.

For example, where my K2 and  the analog meter read 1.4:1, the K3 says
1.9:1.  this variance increases as the SWR increases and decreases as
the actual SWR decreases, hence the agreement among all three measures
on 1:1 when operating into a dummy load.

All readings taken at 5 watts, same antenna, same  SG-237 autocoupler,
same cable routings, and the internal ATU in the K2 bypassed.  The only
variable is the actual 48coax jumper going from the K3 to the patch
panel.

I just finished the K3 yesterday so I am just a K3 beginner. However I
could find nothing in the manual about SWR calibration.

Any pointers would be appreciated.  Other than this, everything appears
to be working great and the K3 DSP is fabulous.

Stan WB2LQF
K3 #5244



73, Ed - KL7UW, WD2XSH/45

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[Elecraft] K3 SWR Readout Accuracy Question

[stan levandowski]

On my newly assembled kit K3/10 without the internal ATU, I've noticed 
that the SWR readouts are higher than those on my K2 which agrees with 
my analog inline meter.  Into a 50 ohm dummy load all three readings are 
1.0:1, but on an actual antenna the readings differ.

For example, where my K2 and  the analog meter read 1.4:1, the K3 says 
1.9:1.  this variance increases as the SWR increases and decreases as 
the actual SWR decreases, hence the agreement among all three measures 
on 1:1 when operating into a dummy load.

All readings taken at 5 watts, same antenna, same  SG-237 autocoupler, 
same cable routings, and the internal ATU in the K2 bypassed.  The only 
variable is the actual 48coax jumper going from the K3 to the patch 
panel.

I just finished the K3 yesterday so I am just a K3 beginner. However I 
could find nothing in the manual about SWR calibration.

Any pointers would be appreciated.  Other than this, everything appears 
to be working great and the K3 DSP is fabulous.

Stan WB2LQF
K3 #5244

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Re: [Elecraft] K3- SWR accuracy

[Jorge Diez - CX6VM]

Hi Bill,

I recently purchased a powerMaster from arraysolutions and have the same
problems.

Readings are different in the Powermaster and in the K3, .3 to .7 in
diference.

You have some coax loops going from SWR and AMP, so maybe some diference
there?.  Anyway is not reading the same...

73,
Jorge
CX6VM/CW5W
K3 #4077

-Mensaje original-
De: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] En nombre de Bill Conkling
Enviado el: Lunes, 06 de Septiembre de 2010 01:25 a.m.
Para: Elecraft@mailman.qth.net
Asunto: [Elecraft] K3- SWR accuracy

Gang, 

 

I have recently built my K3 and have had it on the air about 3 weeks.  I
started small, with 10 watts, added the PA3 and DVR.  My next purchase will
be the ATU module.  In the meantime, I am using an LDG-200Pro Auto-Tuner.
It works great, but I have noticed that especially on 40 meters, I can have
the tuner go through a 'tune' cycle, and it will show 1.0:1 SWR, but my K3
shows 1.3 ro 1.7 up to 1.8 to 1 SWR.

 

I recorded a short call response with the DVR and when I play it back, the
radio shows SWR of more than 1:1 but the tuner indicates full power and low
SWR.  Which do I believe?  Most other bands are normal, with tuner/radio
agreement.   But not always, and especially on 40.

 

I tried to manually tune the tuner to 1:1 and usually only took a couple of
clicks, but no matter what I did, I could not get it to hold those settings;
ie, when I went back to the frequency I 'manually' tuned, and tried to
memorize, it tuned again, often only a Memory Tune, but went back to it's
settings of 1.3:1.

 

Any ideas?

 

...bc  K3  #4536  (nr4c)

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Re: [Elecraft] K3- SWR accuracy

[Bill Conkling]

Gang, 

My antenna is a loop (approx 300 foot, non resonant, nearly horizontal at
average 35 feet)  with 450 ohm ladder line to the window feed thru.  Inside
the window is a 9 length of ladder line, and a balun.  Now six feet of
RG-8X to the LDG and 18 of coax to the K3.

Using the same 18 jumper to the Dummy Load, I get 1:1 all across the bands
on the K3 SWR readout.

...bc

-Original Message-
From: Steve Ellington [mailto:n...@carolina.rr.com] 
Sent: Monday, September 06, 2010 9:18 AM
To: Bill Conkling
Subject: Re: [Elecraft] K3- SWR accuracy

Bill
You probably have some common mode currents on the shield of the coax 
causing the meters to read nutty. I'm curious what kind of feedline and 
antenna you are using and how long is the coax between the K3 and your LDG?
I use an MFJ-998 which is 100 feet from the K3. The meters never read the 
same because of all this coax. The K3's meter is really accurate however. I 
also have the K3 internal tuner and it is really good. Matches almost 
anything.
Steve

- Original Message - 
From: Bill Conkling n...@widomaker.com
To: Elecraft@mailman.qth.net
Sent: Monday, September 06, 2010 12:25 AM
Subject: [Elecraft] K3- SWR accuracy


 Gang,



 I have recently built my K3 and have had it on the air about 3 weeks.  I
 started small, with 10 watts, added the PA3 and DVR.  My next purchase 
 will
 be the ATU module.  In the meantime, I am using an LDG-200Pro Auto-Tuner.
 It works great, but I have noticed that especially on 40 meters, I can 
 have
 the tuner go through a 'tune' cycle, and it will show 1.0:1 SWR, but my K3
 shows 1.3 ro 1.7 up to 1.8 to 1 SWR.



 I recorded a short call response with the DVR and when I play it back, the
 radio shows SWR of more than 1:1 but the tuner indicates full power and 
 low
 SWR.  Which do I believe?  Most other bands are normal, with tuner/radio
 agreement.   But not always, and especially on 40.



 I tried to manually tune the tuner to 1:1 and usually only took a couple 
 of
 clicks, but no matter what I did, I could not get it to hold those 
 settings;
 ie, when I went back to the frequency I 'manually' tuned, and tried to
 memorize, it tuned again, often only a Memory Tune, but went back to it's
 settings of 1.3:1.



 Any ideas?



 ...bc  K3  #4536  (nr4c)

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[Elecraft] K3 SWR reading fault with PA

[John Petters]

Hi Folks,
A problem occured last night.
I have the K3 with the 100 watt PA.
SWR with the QRP amp, i.e. below 12 watts is perfect according to the K3 
meter.
When I increase power the  SWR goes high and so does the current. I 
tried this on dummy load and the same problem exists.
One clue - there was a thunderstorm fairly close by. It was a rumble in 
the distance although the static crashes were loud. Does this indicate I 
may have popped the SWR diodes?
Suggestions appreciated.
73

-- 
John Petters
Amateur Radio Station G3YPZ 
www.traditional-jazz.com

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[Elecraft] K3 SWR reading at low power

[Ramiro Aceves]

Hi all,

Is it normal that my K3 do not show SWR reading on TUNE below 2 W power?

Thanks in advance.

Ramiro, EA4NZ, ex EA1ABZ
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Re: [Elecraft] K3 SWR reading at low power

[Geoffrey Downs]

On TUNE my K3 only shows SWR above 1.9w. Looks like it's normal, Ramiro.

73 to all

Geoff
G3UCK

- Original Message - 
From: Ramiro Aceves ea1...@gmail.com
To: Elecraft@mailman.qth.net
Sent: Thursday, May 06, 2010 8:53 AM
Subject: [Elecraft] K3 SWR reading at low power


 Hi all,
 
 Is it normal that my K3 do not show SWR reading on TUNE below 2 W power?
 
 Thanks in advance.
 
 Ramiro, EA4NZ, ex EA1ABZ
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Re: [Elecraft] K3 - SWR on Tx Gain Calibration

[Geoffrey Downs]

Thanks for the links Bob. I thought I remembered something like that. 
Thanks also to others who have commented.

Maybe the ATU needs to look at a 50 ohm load at some point in its youth in 
order to learn what residual values to leave in circuit when in bypass. I 
use 10m only very rarely so it's likely that I have never shown the ATU a 50 
ohm load on that band. OTOH could it be a malfunction somewhere that is 
being compensated for by ATU residual  values in bypass? I'm not noticing 
any other oddities though.

By the way, Istavenhagen, the relay does click when I change to and from 
bypass. Even on 6m, Bill (W5WVO).

73 to all

Geoff
G3UCK

- Original Message - 
From: Bob Cunnings bob.cunni...@gmail.com


 When in doubt, search the archives!

 http://www.mail-archive.com/elecraft@mailman.qth.net/msg69011.html

 http://www.mail-archive.com/elecraft@mailman.qth.net/msg84916.html


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Re: [Elecraft] K3 - SWR on Tx Gain Calibration

[lstavenhagen]

Well now that I understand what bypass actually is, it makes more sense to me
too. It sounds kind of like the manual method of bypassing the ATU in the
K2, but just automatic. Neato!

73,
LS
W5QD

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Re: [Elecraft] K3 - SWR on Tx Gain Calibration

[Bill VanAlstyne W5WVO]

Interesting, Geoff. Could it be that, since my 6m antenna array is resonant 
and shows 1:1 SWR both on the K3 and on an external power meter, and both 
BEFORE and AFTER I recently installed the KAT3 tuner, maybe the KAT3 doesn't 
actually see any difference in matching requirements between AUTO and BYPASS 
and so therefore doesn't need to switch anything? Nothing to complain about, 
everything works great here on 6m, but it's curious that I don't hear 
anything switching. I'll bet it has to do with the fact that my antenna load 
is flat. Thanks to the MFJ-259B for that. :-)

Bill W5WVO

--
From: Geoffrey Downs geoff...@downs.globalnet.co.uk
Sent: Thursday, May 06, 2010 6:15 AM
To: Bob Cunnings bob.cunni...@gmail.com; elecraft@mailman.qth.net
Subject: Re: [Elecraft] K3 - SWR on Tx Gain Calibration

 By the way, Istavenhagen, the relay does click when I change to and from
 bypass. Even on 6m, Bill (W5WVO).
 


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[Elecraft] K3 swr readings on 10m

[elecraft]

Interestingly while over in england for the weekend installing My wifes K3 I 
had a similar experience 

I was interfacing the new DEMI 70MHz transverter which needed 5W drive at 
10m 

So i set up the transverter to use the antenna 1 connector. When producing 
5W the K3 thought the SWR was 4.5 to 1. Inserting an swr meter between K3 
and xverter showed that the swr was 1.1:1 

as an experiment I engaged the atu, which not surprisingly convinced the k3 
the swr was 1:1. The swr meter still showed 1.1:1 

I then put the ATU into bypass mode and this time it showed swr of 1.1:1 
rather than 4.5:1, which didnt make sense 

Dave 

G4FRE
 
 Message: 10
 Date: Wed, 5 May 2010 14:31:29 +0100
 From: Geoffrey Downs geoff...@downs.globalnet.co.uk
 Subject: [Elecraft]  K3 - SWR on Tx Gain Calibration
 To: elecraft@mailman.qth.net
 Message-ID: aaf7700462664dbf8edbdfb1b6173...@geoff
 Content-Type: text/plain; format=flowed; charset=iso-8859-1;
   reply-type=original 
 
 For some time I've been puzzled that, when doing a TX gain calibration 
 either manually or with the utility, the SWR displayed was 1.0:1 on all 
 bands except for 10m where it was 1.5:1. Yesterday my K3 (Ser. No. 266) had 
 a meeting with a K3 (slightly earlier Ser. No.) belonging to David G4DMP 
 (the owners met too!) and we found that his K3 was the same. 
 
 Now here's the interesting thing. During tx gain calibration a 50 ohm dummy 
 load is used and the ATU is in bypass mode. As an experiment David put his 
 K3's ATU in circuit on 10m and pressed ATU Tune - result (unsurprisingly) 
 1.0:1. He then put the ATU back into bypass mode and held Tune as one would 
 do in a tx gain calibration. Hey presto - 1.0:1! My K3 behaved in exactly 
 the same way and now always displays 1.0:1 on 10m into the dummy load with 
 the ATU in bypass mode. 
 
 Presumably this is something to do with the ATU not being out of circuit 
 when in bypass mode. 
 
 73 to all
 Geoff
 G3UCK  
 
  
 
 -- 
 
 Message: 11
 Date: Wed, 5 May 2010 08:39:34 -0700 (PDT)
 From: lstavenhagen lstavenha...@hotmail.com
 Subject: Re: [Elecraft] K3 - SWR on Tx Gain Calibration
 To: elecraft@mailman.qth.net
 Message-ID: 1273073974914-5009531.p...@n2.nabble.com
 Content-Type: text/plain; charset=us-ascii 
 
 
 For what it's worth, I definitely can't replicate this on my K3. The ATU is
 definitely is bypassed when I select bypass on 10M (in both ANT sockets). 
 Do you hear the relay clicking when you switch back and forth between bypass
 and inline? 
 
 73,
 LS
 W5QD
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 Sent from the Elecraft mailing list archive at Nabble.com. 
 
 
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Re: [Elecraft] K3 SWR reading at low power

[Ramiro Aceves]

Geoffrey Downs escribió:
 On TUNE my K3 only shows SWR above 1.9w. Looks like it's normal, Ramiro.

Thanks very much Geoffrey, I will  sleep well tonight.


 
 73 to all
 
 Geoff
 G3UCK

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[Elecraft] K3 - SWR on Tx Gain Calibration

[Geoffrey Downs]

For some time I've been puzzled that, when doing a TX gain calibration 
either manually or with the utility, the SWR displayed was 1.0:1 on all 
bands except for 10m where it was 1.5:1. Yesterday my K3 (Ser. No. 266) had 
a meeting with a K3 (slightly earlier Ser. No.) belonging to David G4DMP 
(the owners met too!) and we found that his K3 was the same.

Now here's the interesting thing. During tx gain calibration a 50 ohm dummy 
load is used and the ATU is in bypass mode. As an experiment David put his 
K3's ATU in circuit on 10m and pressed ATU Tune - result (unsurprisingly) 
1.0:1. He then put the ATU back into bypass mode and held Tune as one would 
do in a tx gain calibration. Hey presto - 1.0:1! My K3 behaved in exactly 
the same way and now always displays 1.0:1 on 10m into the dummy load with 
the ATU in bypass mode.

Presumably this is something to do with the ATU not being out of circuit 
when in bypass mode.

73 to all
Geoff
G3UCK 

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Re: [Elecraft] K3 - SWR on Tx Gain Calibration

[lstavenhagen]

For what it's worth, I definitely can't replicate this on my K3. The ATU is
definitely is bypassed when I select bypass on 10M (in both ANT sockets). 
Do you hear the relay clicking when you switch back and forth between bypass
and inline?

73,
LS
W5QD
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View this message in context: 
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Re: [Elecraft] K3 - SWR on Tx Gain Calibration

[Mike]

lstavenhagen wrote:
 For what it's worth, I definitely can't replicate this on my K3. The ATU is
 definitely is bypassed when I select bypass on 10M (in both ANT sockets). 
 Do you hear the relay clicking when you switch back and forth between bypass
 and inline?

 73,
 LS
 W5QD
   
I had a question about bypassing the ATU a while back. If I remember 
correctly (put the IF in caps), I was told it is not completely out of 
the circuit when it's bypassed.
Don? Lyle? Wayne?

73, Mike NF4L

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Re: [Elecraft] K3 - SWR on Tx Gain Calibration

[Bill VanAlstyne W5WVO]

FWIW, my K3 does not audibly activate any relays when switching between AUTO 
and BYPASS modes on 6 meters -- but on every other band, it does, you can 
hear it. And the ATU does engage and match on 6 meters when not bypassed. 
Curious.

Bill W5WVO


--
From: lstavenhagen lstavenha...@hotmail.com
Sent: Wednesday, May 05, 2010 9:39 AM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] K3 - SWR on Tx Gain Calibration


 For what it's worth, I definitely can't replicate this on my K3. The ATU 
 is
 definitely is bypassed when I select bypass on 10M (in both ANT sockets).
 Do you hear the relay clicking when you switch back and forth between 
 bypass
 and inline?

 73,
 LS
 W5QD
 -- 
 View this message in context: 
 http://elecraft.365791.n2.nabble.com/K3-SWR-on-Tx-Gain-Calibration-tp5008783p5009531.html
 Sent from the Elecraft mailing list archive at Nabble.com.
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Re: [Elecraft] K3 - SWR on Tx Gain Calibration

[Bob Cunnings]

When in doubt, search the archives!

http://www.mail-archive.com/elecraft@mailman.qth.net/msg69011.html

http://www.mail-archive.com/elecraft@mailman.qth.net/msg84916.html

Bob NW8L


On Wed, May 5, 2010 at 11:07 AM, Mike n...@nf4l.com wrote:
 lstavenhagen wrote:
 For what it's worth, I definitely can't replicate this on my K3. The ATU is
 definitely is bypassed when I select bypass on 10M (in both ANT sockets).
 Do you hear the relay clicking when you switch back and forth between bypass
 and inline?

 73,
 LS
 W5QD

 I had a question about bypassing the ATU a while back. If I remember
 correctly (put the IF in caps), I was told it is not completely out of
 the circuit when it's bypassed.
 Don? Lyle? Wayne?

 73, Mike NF4L

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Re: [Elecraft] K3 SWR error

[Radio Amateur N5GE]

On Sun, 14 Mar 2010 10:19:28 -0800 (PST), NZ0T n...@cox.net wrote:

How much inaccuracy are you experiencing?

How did you determine that the K3 is inaccurate?  How did you
determine that the W2 is very accurate?


I have K3-100 kit 1502 with the internal tuner and FW 3.76.  I know there
have been many posts about the meter SWR error but I really haven't seen a
resolution posted.  Before I bought my W2 I used a cheap SWR/Power meter and
I thought the error was in it.  Now that I have the W2 (which appears to be
very accurate) I see that the K3 SWR indication can be very different than
my W2, Ten Tec tuner, analyzer and my other HF rigs with or without the
internal tuner in line.  My concern is that if the K3 reads SWR incorrectly
that the power may not fold back and there may be a risk of damage to the
finals.  Is there any procedure to correct the error?  I understand that
stray capacitance can cause differences but I would really like to have a
more accurate measurement by the rig.

Tom, N5GE

K3 #806 with SUB RX, PR6, 
KRC2 and K144XV
K3 #1055 with PR6 and XV432
W1, 2 W2's and other small kits

http://www.n5ge.com
http://www.swotrc.net

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Re: [Elecraft] K3 SWR error

[NZ0T]

It depends on band but sometimes I see 2.5 on the W2 (verified by my 
analyzer and SWR meters in my Ten Tec tuner and a TS-940S) but 1.5 or so on 
the K3.  For the most part the K3 shows a lower SWR than any of the rest of 
my meters.  And, for the most part my W2 agrees cloely with my analyzer, 
940, tuner and W2.  An example - on 80 meters:
K3  1.4
Analyzer  1.9
Tuner  1.9
940 2.1
W2 2.1

Maybe I'm making a big deal out of nothing but the 80 meter results are 
pretty typical for each band with the K3 lower that the others that are all 
fairly close to each other.

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Re: [Elecraft] K3 SWR error

[Guy Olinger K2AV]

You probably have extra cable to the K3 from the W2, going through an
amp, etc.

What happens to the difference in SWR if you take the cable from the
OUTPUT of the W2, and connect it directly to the back of the K3?

73, Guy.

On Mon, Mar 15, 2010 at 1:35 PM, NZ0T n...@cox.net wrote:

 It depends on band but sometimes I see 2.5 on the W2 (verified by my
 analyzer and SWR meters in my Ten Tec tuner and a TS-940S) but 1.5 or so on
 the K3.  For the most part the K3 shows a lower SWR than any of the rest of
 my meters.  And, for the most part my W2 agrees cloely with my analyzer,
 940, tuner and W2.  An example - on 80 meters:
 K3  1.4
 Analyzer  1.9
 Tuner      1.9
 940         2.1
 W2         2.1

 Maybe I'm making a big deal out of nothing but the 80 meter results are
 pretty typical for each band with the K3 lower that the others that are all
 fairly close to each other.

 --
 View this message in context: 
 http://n2.nabble.com/K3-SWR-error-tp4732831p4738535.html
 Sent from the [K3] mailing list archive at Nabble.com.
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Re: [Elecraft] K3 SWR error

[Bill K9YEQ]

I allow some deviation knowing that at different places along the cable, the
swr will be different.  This includes equipment like amplifiers.  If the
deviation isn't more than 1.2, then I am happy, otherwise I readjust.  You
could calibrate the W2 but then I think it changes the actual.  Looking for
pure 1.0:1 isn't always real.  

Bill
K9YEQ

-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Guy Olinger K2AV
Sent: Monday, March 15, 2010 1:47 PM
To: NZ0T
Cc: elecraft@mailman.qth.net
Subject: Re: [Elecraft] K3 SWR error

You probably have extra cable to the K3 from the W2, going through an
amp, etc.

What happens to the difference in SWR if you take the cable from the
OUTPUT of the W2, and connect it directly to the back of the K3?

73, Guy.

On Mon, Mar 15, 2010 at 1:35 PM, NZ0T n...@cox.net wrote:

 It depends on band but sometimes I see 2.5 on the W2 (verified by my
 analyzer and SWR meters in my Ten Tec tuner and a TS-940S) but 1.5 or so
on
 the K3.  For the most part the K3 shows a lower SWR than any of the rest
of
 my meters.  And, for the most part my W2 agrees cloely with my analyzer,
 940, tuner and W2.  An example - on 80 meters:
 K3  1.4
 Analyzer  1.9
 Tuner      1.9
 940         2.1
 W2         2.1

 Maybe I'm making a big deal out of nothing but the 80 meter results are
 pretty typical for each band with the K3 lower that the others that are
all
 fairly close to each other.

 --
 View this message in context:
http://n2.nabble.com/K3-SWR-error-tp4732831p4738535.html
 Sent from the [K3] mailing list archive at Nabble.com.
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[Elecraft] K3 SWR error

[NZ0T]

I have K3-100 kit 1502 with the internal tuner and FW 3.76.  I know there
have been many posts about the meter SWR error but I really haven't seen a
resolution posted.  Before I bought my W2 I used a cheap SWR/Power meter and
I thought the error was in it.  Now that I have the W2 (which appears to be
very accurate) I see that the K3 SWR indication can be very different than
my W2, Ten Tec tuner, analyzer and my other HF rigs with or without the
internal tuner in line.  My concern is that if the K3 reads SWR incorrectly
that the power may not fold back and there may be a risk of damage to the
finals.  Is there any procedure to correct the error?  I understand that
stray capacitance can cause differences but I would really like to have a
more accurate measurement by the rig.
-- 
View this message in context: 
http://n2.nabble.com/K3-SWR-error-tp4732831p4732831.html
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[Elecraft] K3 SWR Accuracy - reprise

[Stewart]

Hi Jack,
Thank you for the time and effort you spent on making and reporting measurements
on the K3 SWR accuracy. You have saved me from the chore of further 
investigations.

It is interesting to note the close degree of correlation between the 
measurements that you made
using calibrated high accuracy components, and mine made with more run of the 
mill items.

In addition your results show just what a small effect some of the parasitic 
effects like the length
of coax used and the LP-100 coupler being in circuit have on overall 
measurement accuracy.

It maybe that Wayne can make changes to the firmware to compensate for the KAT3 
strays.

I would have thought that as the KAT3 is a factory produced item the variation 
in strays between
individual units would be minimal, and therefore a high SWR measurement 
repeatability
could be achieved.

73
Stewart G3RXQ

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Re: [Elecraft] K3 SWR Accuracy - reprise

[N8LP]

Will the revision be generic to the extent that it will also improve the
readings for radios without the KAT3? My variations are not as great as
Jack's, I suspect due to not having the KAT3, but my readings are
consistently lower than Jack's, ie. 1.6 on most bands with a 2.0 load. Not a
big deal, but as long as you're in there tweaking the code, can you verify
that it works with non-KAT3 radios as well?

73,
Larry N8LP




wayne burdick wrote:
 
 Great data, Jack. We've been testing this, too, and we know why the  
 K3's readings differ.
 
 A firmware change will be made to improve the accuracy in general. But  
 part of the difference on the higher bands is due to strays in the  
 KAT3 module. These strays can be tuned out by the KAT3 itself, thus  
 presenting the correct load to the K3 internally. But an external  
 instrument is on the other side of the KAT3 and thus sees a slightly  
 different match.
 
 We'll post additional details soon. Meanwhile, no one need worry about  
 this apparent discrepancy. The ATU is cancelling its own strays, and  
 the SWR bridge is correctly reporting the load presented to the  
 transceiver internally, which is the important thing when matching the  
 rig to its load.
 
 73,
 Wayne
 N6KR
 
 
 
 http://www.elecraft.com
 
 On Nov 8, 2009, at 7:18 PM, Edward Dickinson, III
 softb...@windstream.net 
   wrote:
 
  _

 From: Jack Smith [mailto:jack.sm...@cliftonlaboratories.com]
 Sent: Sunday, November 08, 2009 10:00 PM
 To: Edward Dickinson, III
 Subject: Re: [Elecraft] K3 SWR Accuracy - reprise

 Dick:

 http://www.cliftonlaboratories.com/swr_accuracy.htm

 I posted a message to the Elecraft reflector about the page being  
 available
 but it has not shown up after an hour and a half.

 Jack K8ZOA


 Edward Dickinson, III wrote:

 Hi Jack.



 I extend invitation to apply your expertise regarding the matter being

 addressed in above referenced discussion.





 Best regards,



 Dick - KA5KKT









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Re: [Elecraft] K3 SWR Accuracy - reprise

[Bob Cunnings]

Speaking of the KAT3, Jack's report doesn't state whether or not his
K3 contains the KAT3 module or not, and what state it's in.

Bob NW8L

On Sun, Nov 8, 2009 at 9:07 PM, Wayne Burdick n...@elecraft.com wrote:
 Great data, Jack. We've been testing this, too, and we know why the
 K3's readings differ.

 A firmware change will be made to improve the accuracy in general. But
 part of the difference on the higher bands is due to strays in the
 KAT3 module. These strays can be tuned out by the KAT3 itself, thus
 presenting the correct load to the K3 internally. But an external
 instrument is on the other side of the KAT3 and thus sees a slightly
 different match.

 We'll post additional details soon. Meanwhile, no one need worry about
 this apparent discrepancy. The ATU is cancelling its own strays, and
 the SWR bridge is correctly reporting the load presented to the
 transceiver internally, which is the important thing when matching the
 rig to its load.

 73,
 Wayne
 N6KR


 
 http://www.elecraft.com

 On Nov 8, 2009, at 7:18 PM, Edward Dickinson, III softb...@windstream.net
   wrote:

  _

 From: Jack Smith [mailto:jack.sm...@cliftonlaboratories.com]
 Sent: Sunday, November 08, 2009 10:00 PM
 To: Edward Dickinson, III
 Subject: Re: [Elecraft] K3 SWR Accuracy - reprise

 Dick:

 http://www.cliftonlaboratories.com/swr_accuracy.htm

 I posted a message to the Elecraft reflector about the page being
 available
 but it has not shown up after an hour and a half.

 Jack K8ZOA


 Edward Dickinson, III wrote:

 Hi Jack.



 I extend invitation to apply your expertise regarding the matter being

 addressed in above referenced discussion.





 Best regards,



 Dick - KA5KKT









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Re: [Elecraft] K3 SWR Accuracy - reprise

[Paul Christensen]

 consistently lower than Jack's, ie. 1.6 on most bands with a 2.0 load. Not 
 a
 big deal, but as long as you're in there tweaking the code, can you verify
 that it works with non-KAT3 radios as well?

I'm curious -- are those who see a smaller indicated VSWR reading on the K3 
meter with a 25-ohm load seeing the same discrepancy with a 100-ohm load? 
This may partially explain why some owners are seeing varying results under 
a 2:1 VSWR since that ratio can be comprised of those two resistance loads 
or an infinite set of resistive + reactive conditions -- any of which can 
form a load impedance of 25 or 100 ohms.

Paul, W9AC

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Re: [Elecraft] K3 SWR Accuracy - reprise

[N8LP]

He does have the KAT3, and it was in bypass for the tests.

Larry N8LP




Bob Cunnings wrote:
 
 Speaking of the KAT3, Jack's report doesn't state whether or not his
 K3 contains the KAT3 module or not, and what state it's in.
 
 Bob NW8L
 
 On Sun, Nov 8, 2009 at 9:07 PM, Wayne Burdick n...@elecraft.com wrote:
 Great data, Jack. We've been testing this, too, and we know why the
 K3's readings differ.

 A firmware change will be made to improve the accuracy in general. But
 part of the difference on the higher bands is due to strays in the
 KAT3 module. These strays can be tuned out by the KAT3 itself, thus
 presenting the correct load to the K3 internally. But an external
 instrument is on the other side of the KAT3 and thus sees a slightly
 different match.

 We'll post additional details soon. Meanwhile, no one need worry about
 this apparent discrepancy. The ATU is cancelling its own strays, and
 the SWR bridge is correctly reporting the load presented to the
 transceiver internally, which is the important thing when matching the
 rig to its load.

 73,
 Wayne
 N6KR


 
 http://www.elecraft.com

 On Nov 8, 2009, at 7:18 PM, Edward Dickinson, III
 softb...@windstream.net
   wrote:

  _

 From: Jack Smith [mailto:jack.sm...@cliftonlaboratories.com]
 Sent: Sunday, November 08, 2009 10:00 PM
 To: Edward Dickinson, III
 Subject: Re: [Elecraft] K3 SWR Accuracy - reprise

 Dick:

 http://www.cliftonlaboratories.com/swr_accuracy.htm

 I posted a message to the Elecraft reflector about the page being
 available
 but it has not shown up after an hour and a half.

 Jack K8ZOA


 Edward Dickinson, III wrote:

 Hi Jack.



 I extend invitation to apply your expertise regarding the matter being

 addressed in above referenced discussion.





 Best regards,



 Dick - KA5KKT









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Re: [Elecraft] K3 SWR Accuracy - reprise

[N8LP]

That's a good question, Paul. I have a medium power, 150 ohm load laying
around that I made up a couple years ago for testing purposes. I just
checked it with my VNA and it has an SWR of 2.92, pure resistive. I did a
quick test with the K3 at 25W, and it measured between 2.4 and 2.7 depending
on band. That's about the same percentage error as the 25 ohm load, but it's
impossible to know if the error is in the same direction. I would think that
you could calculate the direction using the tuned L-network values of a
KAT3, but I don't have one installed. 

Larry N8LP



P.B. Christensen wrote:
 
 consistently lower than Jack's, ie. 1.6 on most bands with a 2.0 load.
 Not 
 a
 big deal, but as long as you're in there tweaking the code, can you
 verify
 that it works with non-KAT3 radios as well?
 
 I'm curious -- are those who see a smaller indicated VSWR reading on the
 K3 
 meter with a 25-ohm load seeing the same discrepancy with a 100-ohm load? 
 This may partially explain why some owners are seeing varying results
 under 
 a 2:1 VSWR since that ratio can be comprised of those two resistance loads 
 or an infinite set of resistive + reactive conditions -- any of which can 
 form a load impedance of 25 or 100 ohms.
 
 Paul, W9AC
 
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[Elecraft] K3 SWR Accuracy: Final explanation

[Wayne Burdick]

There are two sources of the reported SWR inaccuracies:

- An SWR calculation scalar that I'll be adjusting in firmware; this  
is what's causing a 2:1 SWR to read closer to 1.8:1 on some K3s.

- The KAT3 itself, and to a much lesser degree, the KANT3, which is  
present if the ATU is not installed. Both modules have inherent stray  
reactance, part of which is due to the 8.2 MHz first-IF trap. These  
strays slightly alter the impedance seen by the K3's SWR bridge.

Even when the scalar correction is applied, there will still be a  
small frequency-dependent variation in SWR reading between the K3's  
bridge and an external instrument. This has no impact on K3 operation.

73,
Wayne
N6KR


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Re: [Elecraft] K3 SWR Accuracy - reprise

[Jack Smith]

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Re: [Elecraft] K3 SWR Accuracy: Final explanation

[Jack Smith]

Wayne:

There's also an SWR versus output power issue, or is that part of the 
first correction factor? The SWR error increases significantly at lower 
power. I have not had a chance to plot the data because it was not part 
of the original question, but there is a clear power related error seen 
in the raw data, which I assume is tied to the detector diode linearity 
at low voltages.

Jack K8ZOA


Wayne Burdick wrote:
 There are two sources of the reported SWR inaccuracies:

 - An SWR calculation scalar that I'll be adjusting in firmware; this  
 is what's causing a 2:1 SWR to read closer to 1.8:1 on some K3s.

 - The KAT3 itself, and to a much lesser degree, the KANT3, which is  
 present if the ATU is not installed. Both modules have inherent stray  
 reactance, part of which is due to the 8.2 MHz first-IF trap. These  
 strays slightly alter the impedance seen by the K3's SWR bridge.

 Even when the scalar correction is applied, there will still be a  
 small frequency-dependent variation in SWR reading between the K3's  
 bridge and an external instrument. This has no impact on K3 operation.

 73,
 Wayne
 N6KR


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Re: [Elecraft] K3 SWR Accuracy - reprise

[Jack Smith]

I'm running tests today with the 25 ohm load connected to  the K3/LP-100 
with varying lengths of RG-142B/U coaxial cable, in 24 inch increments 
out to 120 or 144 inches. The result should be a constant SWR, 
neglecting the padding effect of coaxial cable loss, but with the 
impedance varying along the constant  SWR circle if we think in Smith 
chart terms.

I will also measure the R+jX of the load under the same conditions, with 
both the LP-100 and a VNA.

I may have the data analyzed this evening, but more likely tomorrow.

Also added a note confirming that my K3 has the KAT3  tuner, set to 
BYPASS for the tests.

Jack


N8LP wrote:
 That's a good question, Paul. I have a medium power, 150 ohm load laying
 around that I made up a couple years ago for testing purposes. I just
 checked it with my VNA and it has an SWR of 2.92, pure resistive. I did a
 quick test with the K3 at 25W, and it measured between 2.4 and 2.7 depending
 on band. That's about the same percentage error as the 25 ohm load, but it's
 impossible to know if the error is in the same direction. I would think that
 you could calculate the direction using the tuned L-network values of a
 KAT3, but I don't have one installed. 

 Larry N8LP



 P.B. Christensen wrote:
   
 consistently lower than Jack's, ie. 1.6 on most bands with a 2.0 load.
 Not 
 a
 big deal, but as long as you're in there tweaking the code, can you
 verify
 that it works with non-KAT3 radios as well?
   
 I'm curious -- are those who see a smaller indicated VSWR reading on the
 K3 
 meter with a 25-ohm load seeing the same discrepancy with a 100-ohm load? 
 This may partially explain why some owners are seeing varying results
 under 
 a 2:1 VSWR since that ratio can be comprised of those two resistance loads 
 or an infinite set of resistive + reactive conditions -- any of which can 
 form a load impedance of 25 or 100 ohms.

 Paul, W9AC

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Re: [Elecraft] K3 SWR Accuracy: Final explanation

[Wayne Burdick]

There's no way to avoid some increase in SWR reading error at low  
power, since the bridge transformers have a low coupling ratio to  
avoid heating at full power. We're already using very low-drop diodes  
and pre-biasing them.

That said, I am going to look at a correction based on power level if  
possible.

tnx
Wayne
N6KR

On Nov 9, 2009, at 9:06 AM, Jack Smith wrote:

 Wayne:

 There's also an SWR versus output power issue, or is that part of  
 the first correction factor? The SWR error increases significantly  
 at lower power. I have not had a chance to plot the data because it  
 was not part of the original question, but there is a clear power  
 related error seen in the raw data, which I assume is tied to the  
 detector diode linearity at low voltages.

 Jack K8ZOA


 Wayne Burdick wrote:
 There are two sources of the reported SWR inaccuracies:

 - An SWR calculation scalar that I'll be adjusting in firmware;  
 this  is what's causing a 2:1 SWR to read closer to 1.8:1 on some  
 K3s.

 - The KAT3 itself, and to a much lesser degree, the KANT3, which  
 is  present if the ATU is not installed. Both modules have inherent  
 stray  reactance, part of which is due to the 8.2 MHz first-IF  
 trap. These  strays slightly alter the impedance seen by the K3's  
 SWR bridge.

 Even when the scalar correction is applied, there will still be a   
 small frequency-dependent variation in SWR reading between the  
 K3's  bridge and an external instrument. This has no impact on K3  
 operation.

 73,
 Wayne
 N6KR


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Re: [Elecraft] K3 SWR Accuracy: Final explanation

[Duncan Carter]

Does part of the K3 spec mention that it's supposed to be a precision 
swr indicator?  If so, I missed that.  I thought that I was merely 
getting an outstanding transceiver, especially for cw, at a relatively 
low cost.

This year, I became active on ham radio after a multi-decade hiatus.  
Before I left, the normal assumption about swr meters with diodes was 
that they had reduced accuracy at low power levels because of diode 
non-linearities.  Has this changed while I was away?

73, Dunc, W5DC

Wayne Burdick wrote:
 There's no way to avoid some increase in SWR reading error at low  
 power, since the bridge transformers have a low coupling ratio to  
 avoid heating at full power. We're already using very low-drop diodes  
 and pre-biasing them.

 That said, I am going to look at a correction based on power level if  
 possible.

 tnx
 Wayne
 N6KR

 On Nov 9, 2009, at 9:06 AM, Jack Smith wrote:

   
 Wayne:

 There's also an SWR versus output power issue, or is that part of  
 the first correction factor? The SWR error increases significantly  
 at lower power. I have not had a chance to plot the data because it  
 was not part of the original question, but there is a clear power  
 related error seen in the raw data, which I assume is tied to the  
 detector diode linearity at low voltages.

 Jack K8ZOA


 Wayne Burdick wrote:
 
 There are two sources of the reported SWR inaccuracies:

 - An SWR calculation scalar that I'll be adjusting in firmware;  
 this  is what's causing a 2:1 SWR to read closer to 1.8:1 on some  
 K3s.

 - The KAT3 itself, and to a much lesser degree, the KANT3, which  
 is  present if the ATU is not installed. Both modules have inherent  
 stray  reactance, part of which is due to the 8.2 MHz first-IF  
 trap. These  strays slightly alter the impedance seen by the K3's  
 SWR bridge.

 Even when the scalar correction is applied, there will still be a   
 small frequency-dependent variation in SWR reading between the  
 K3's  bridge and an external instrument. This has no impact on K3  
 operation.

 73,
 Wayne
 N6KR


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[Elecraft] [K3] SWR

[Al Lorona]

...Does part of the K3 spec mention that it's supposed to be a precision 
swr indicator?...  

73, Dunc, W5DC


I am shocked and dismayed that the SWR indicator in the K3 does not, after all, 
rival an external, laboratory-grade instrument. This is a 
tremendously disturbing disappointment for me.

In this state of dejection and disillusionment, and hoping to assuage my 
sorrow, I set out to verify some of the other controls on the K3 that I had 
assumed would be absolutely accurate.

To my horror, I must now report -- with extreme reluctance-- that the CW speed 
control under-reports the CW speed by 2 WPM! How can this be? Wayne, I demand 
an immediate explanation. 

That was bad enough, but that's not all. To add seeming insult to injury, I 
have now found that when my CW pitch is set to 600 Hz the actual measured pitch 
is closer to 608 Hz. Instead of a D, it's more like an E-flat. Certainly, none 
of us is going to stand for that.

If these two conditions are not corrected in the next release I'm going back to 
my Kensucom MarkTwoDoublePlusGee.

I really thought that the K3 was a perfect rig in a perfect world, but I am 
utterly crushed to find that it is a merely great one in an imperfect world. 
Darn.

W6LX said that.
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Re: [Elecraft] [K3] SWR

[Duncan Carter]

Al,
Here's another complaint.  It seems the Elecraft refelector is stripping 
the .dripping with (welldeserved) sarcasm tag from your post just like 
it did the same to my last post. On the other hand, my audio spectrum 
analyzer reports the cw pitch as 600 Hz; I use it routinely because I 
like it better than Elecraft's CWT. 

I do still have my FT-101E in reserve if the K3 faults become too much 
to tolerate.

73, Dunc, W5DC

Al Lorona wrote:
 
 ...Does part of the K3 spec mention that it's supposed to be a precision 
 swr indicator?...  

 73, Dunc, W5DC
 

 I am shocked and dismayed that the SWR indicator in the K3 does not, after 
 all, rival an external, laboratory-grade instrument. This is a tremendously 
 disturbing disappointment for me.

 In this state of dejection and disillusionment, and hoping to assuage my 
 sorrow, I set out to verify some of the other controls on the K3 that I had 
 assumed would be absolutely accurate.

 To my horror, I must now report -- with extreme reluctance-- that the CW 
 speed control under-reports the CW speed by 2 WPM! How can this be? Wayne, I 
 demand an immediate explanation. 

 That was bad enough, but that's not all. To add seeming insult to injury, I 
 have now found that when my CW pitch is set to 600 Hz the actual measured 
 pitch is closer to 608 Hz. Instead of a D, it's more like an E-flat. 
 Certainly, none of us is going to stand for that.

 If these two conditions are not corrected in the next release I'm going back 
 to my Kensucom MarkTwoDoublePlusGee.

 I really thought that the K3 was a perfect rig in a perfect world, but I am 
 utterly crushed to find that it is a merely great one in an imperfect world. 
 Darn.

 W6LX said that.
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Re: [Elecraft] [K3] SWR

[Don Wilhelm]

Duncan,

AND, *my* K3 gets dust on the plastic covering the LCD display.  I 
really don't know why this has not been corrected by adding a sprayer 
and wipers to keep it clean.  After all, every auto in the US has such a 
device, it should not be difficult to add on the K3 as well to assure a 
clean display.  If the K3 is to be perfect, it should keep itself 
perfectly clean too.

73,
Don W3FPR

Duncan Carter wrote:
 Al,
 Here's another complaint.  It seems the Elecraft refelector is stripping 
 the .dripping with (welldeserved) sarcasm tag from your post just like 
 it did the same to my last post. On the other hand, my audio spectrum 
 analyzer reports the cw pitch as 600 Hz; I use it routinely because I 
 like it better than Elecraft's CWT. 

 I do still have my FT-101E in reserve if the K3 faults become too much 
 to tolerate.

 73, Dunc, W5DC

 Al Lorona wrote:
   
 
 ...Does part of the K3 spec mention that it's supposed to be a precision 
 swr indicator?...  

 73, Dunc, W5DC
 

 I am shocked and dismayed that the SWR indicator in the K3 does not, after 
 all, rival an external, laboratory-grade instrument. This is a tremendously 
 disturbing disappointment for me.

 

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Re: [Elecraft] K3 SWR Accuracy - reprise

[Wayne Burdick]

Great data, Jack. We've been testing this, too, and we know why the  
K3's readings differ.

A firmware change will be made to improve the accuracy in general. But  
part of the difference on the higher bands is due to strays in the  
KAT3 module. These strays can be tuned out by the KAT3 itself, thus  
presenting the correct load to the K3 internally. But an external  
instrument is on the other side of the KAT3 and thus sees a slightly  
different match.

We'll post additional details soon. Meanwhile, no one need worry about  
this apparent discrepancy. The ATU is cancelling its own strays, and  
the SWR bridge is correctly reporting the load presented to the  
transceiver internally, which is the important thing when matching the  
rig to its load.

73,
Wayne
N6KR



http://www.elecraft.com

On Nov 8, 2009, at 7:18 PM, Edward Dickinson, III softb...@windstream.net 
  wrote:

  _

 From: Jack Smith [mailto:jack.sm...@cliftonlaboratories.com]
 Sent: Sunday, November 08, 2009 10:00 PM
 To: Edward Dickinson, III
 Subject: Re: [Elecraft] K3 SWR Accuracy - reprise

 Dick:

 http://www.cliftonlaboratories.com/swr_accuracy.htm

 I posted a message to the Elecraft reflector about the page being  
 available
 but it has not shown up after an hour and a half.

 Jack K8ZOA


 Edward Dickinson, III wrote:

 Hi Jack.



 I extend invitation to apply your expertise regarding the matter being

 addressed in above referenced discussion.





 Best regards,



 Dick - KA5KKT









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Re: [Elecraft] K3 SWR Accuracy - reprise

[Dave G4AON]

Wayne (and Jack) I and at least one other user, have noted the K3 with
ATU sometimes appears to leave a residual C or L in circuit on 10m when
in bypass giving lower than expected power into a 50 Ohm load and may
give incorrect TX power calibration as a result. Using the ATU to give a
good SWR fixed the problem. The residual issue isn't always there, the
typical false SWR is 1.5:1 or 1.6:1.

73 Dave, G4AON
K3/100 #80
--
We'll post additional details soon. Meanwhile, no one need worry about
this apparent discrepancy. The ATU is cancelling its own strays, and
the SWR bridge is correctly reporting the load presented to the
transceiver internally, which is the important thing when matching the
rig to its load.

73,
Wayne
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[Elecraft] K3 SWR Accuracy - reprise

[Stewart]

Hi,
Now traffic on the new K3 Macro functions has somewhat died down, 
I would like to raise again the issue of the K3's SWR measurement 
accuracy.

I did some tests using dummy loads and a LP-100 meter as follows.

The dummy load is a precision 100W one which I measured with a VNA
and has a VSWR of 1.03 from 1 to 30 Mhz. To simulate a 2:1 VSWR
I used another dummy load (not quite as good) in parallel.

The K3 output was from ANT1 using the internal ATU. The ATU was
automatically tuned to 1:1 on all bands.
The results I got for 2:1 VSWR are as follows:-

   LP-100   K3
160 1.991.8
80   1.991.8
60   1.991.8
40   1.951.8
30   1.971.6
20   1.971.4
17   1.971.3
15   1.961.2
12   1.961.5
10   1.961.4  

As can be seen my K3 SWR indication consistently under reads.
However, it really gets bad on 20,17  15.

 From previous replies I understand that this under reading would  
be compensated for in the firmware, sometime in the future . 

Is this still on the list of problems to be addressed ?

73
Stewart G3RXQ
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Re: [Elecraft] K3 SWR Accuracy - reprise

[Robert Naumann]

Just curious how you know that the LP100 is accurate?

-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Stewart
Sent: Wednesday, November 04, 2009 2:45 AM
To: Elecraft Reflector
Subject: [Elecraft] K3 SWR Accuracy - reprise

Hi,
Now traffic on the new K3 Macro functions has somewhat died down, 
I would like to raise again the issue of the K3's SWR measurement 
accuracy.

I did some tests using dummy loads and a LP-100 meter as follows.

The dummy load is a precision 100W one which I measured with a VNA
and has a VSWR of 1.03 from 1 to 30 Mhz. To simulate a 2:1 VSWR
I used another dummy load (not quite as good) in parallel.

The K3 output was from ANT1 using the internal ATU. The ATU was
automatically tuned to 1:1 on all bands.
The results I got for 2:1 VSWR are as follows:-

   LP-100   K3
160 1.991.8
80   1.991.8
60   1.991.8
40   1.951.8
30   1.971.6
20   1.971.4
17   1.971.3
15   1.961.2
12   1.961.5
10   1.961.4  

As can be seen my K3 SWR indication consistently under reads.
However, it really gets bad on 20,17  15.

 From previous replies I understand that this under reading would  
be compensated for in the firmware, sometime in the future . 

Is this still on the list of problems to be addressed ?

73
Stewart G3RXQ

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Re: [Elecraft] K3 SWR Accuracy - reprise

[Robert Naumann]

After reading your table and comments again, I'm also curious why you are
using the antenna tuner in these measurements?

Shouldn't the internal ATU be OFF in order to evaluate the SWR meter?

With the tuner on, the K3's SWR meter is showing the results of the tuner
doing it's job - no? I would hope that the K3 SWR meter would read different
in this case.


-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Stewart
Sent: Wednesday, November 04, 2009 2:45 AM
To: Elecraft Reflector
Subject: [Elecraft] K3 SWR Accuracy - reprise

Hi,
Now traffic on the new K3 Macro functions has somewhat died down, 
I would like to raise again the issue of the K3's SWR measurement 
accuracy.

I did some tests using dummy loads and a LP-100 meter as follows.

The dummy load is a precision 100W one which I measured with a VNA
and has a VSWR of 1.03 from 1 to 30 Mhz. To simulate a 2:1 VSWR
I used another dummy load (not quite as good) in parallel.

The K3 output was from ANT1 using the internal ATU. The ATU was
automatically tuned to 1:1 on all bands.
The results I got for 2:1 VSWR are as follows:-

   LP-100   K3
160 1.991.8
80   1.991.8
60   1.991.8
40   1.951.8
30   1.971.6
20   1.971.4
17   1.971.3
15   1.961.2
12   1.961.5
10   1.961.4  

As can be seen my K3 SWR indication consistently under reads.
However, it really gets bad on 20,17  15.

 From previous replies I understand that this under reading would  
be compensated for in the firmware, sometime in the future . 

Is this still on the list of problems to be addressed ?

73
Stewart G3RXQ
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Re: [Elecraft] K3 SWR Accuracy - reprise

[Stewart]

Of course Robert, the ATU was OFF. My typing error.
Any measurements made with it ON would be meaningless.

73
Stewart G3RXQ 
On Wed, 4 Nov 2009 07:14:43 -0600, Robert Naumann wrote:
 After reading your table and comments again, I'm also curious 
why you are
 using the antenna tuner in these measurements?

 Shouldn't the internal ATU be OFF in order to evaluate the SWR 
meter?

 With the tuner on, the K3's SWR meter is showing the results of 
the tuner
 doing it's job - no? I would hope that the K3 SWR meter would 
read different
 in this case.


 -Original Message-
 From: elecraft-boun...@mailman.qth.net
 [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Stewart
 Sent: Wednesday, November 04, 2009 2:45 AM
 To: Elecraft Reflector
 Subject: [Elecraft] K3 SWR Accuracy - reprise

 Hi,
 Now traffic on the new K3 Macro functions has somewhat died 
down,
 I would like to raise again the issue of the K3's SWR 
measurement
 accuracy.

 I did some tests using dummy loads and a LP-100 meter as 
follows.

 The dummy load is a precision 100W one which I measured with a 
VNA
 and has a VSWR of 1.03 from 1 to 30 Mhz. To simulate a 2:1 VSWR
 I used another dummy load (not quite as good) in parallel.

 The K3 output was from ANT1 using the internal ATU. The ATU was
 automatically tuned to 1:1 on all bands.
 The results I got for 2:1 VSWR are as follows:-

   LP-100   K3
 160 1.991.8
 80   1.991.8
 60   1.991.8
 40   1.951.8
 30   1.971.6
 20   1.971.4
 17   1.971.3
 15   1.961.2
 12   1.961.5
 10   1.961.4

 As can be seen my K3 SWR indication consistently under reads.
 However, it really gets bad on 20,17  15.

 From previous replies I understand that this under reading would
 be compensated for in the firmware, sometime in the future .

 Is this still on the list of problems to be addressed ?

 73
 Stewart G3RXQ
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 Elecraft mailing list
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 Post: mailto:Elecraft@mailman.qth.net

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Re: [Elecraft] K3 SWR Accuracy - reprise

[Wes Stewart]

I suggest a reading of Larry's original paper on the design of the LP-100 to 
understand the heroic efforts needed to make these measurements with any 
accuracy.

see: http://www.telepostinc.com/Files/phipps-1.pdf

It should come as no surprise that the K3's built-in directional coupler lacks 
the directivity of the ones in Larry's LP-100, and directivity is extremely 
important in this application.

For an example left to the reader to work out, measure a load with 20 dB return 
loss using a coupler with 20 dB directivity and see what the uncertainty is.

Wes Stewart  N7WS

--- On Wed, 11/4/09, Stewart stew...@baker.nildram.co.uk wrote:

From: Stewart stew...@baker.nildram.co.uk
Subject: [Elecraft] K3 SWR Accuracy - reprise
To: Elecraft Reflector elecraft@mailman.qth.net
Date: Wednesday, November 4, 2009, 1:44 AM

Hi,
Now traffic on the new K3 Macro functions has somewhat died down, 
I would like to raise again the issue of the K3's SWR measurement 
accuracy.

I did some tests using dummy loads and a LP-100 meter as follows.

The dummy load is a precision 100W one which I measured with a VNA
and has a VSWR of 1.03 from 1 to 30 Mhz. To simulate a 2:1 VSWR
I used another dummy load (not quite as good) in parallel.

The K3 output was from ANT1 using the internal ATU. The ATU was
automatically tuned to 1:1 on all bands.
The results I got for 2:1 VSWR are as follows:-

               LP-100           K3
160         1.99                1.8
80           1.99                1.8
60           1.99                1.8
40           1.95                1.8
30           1.97                1.6
20           1.97                1.4
17           1.97                1.3
15           1.96                1.2
12           1.96                1.5
10           1.96                1.4  

As can be seen my K3 SWR indication consistently under reads.
However, it really gets bad on 20,17  15.

 From previous replies I understand that this under reading would  
be compensated for in the firmware, sometime in the future . 

Is this still on the list of problems to be addressed ?

73
Stewart G3RXQ
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Re: [Elecraft] K3 SWR Accuracy - reprise

[Don Wilhelm]

Wes and all,

It is not unreasonable to expect some frequency dependency in the 
detection diodes as well.
The tuner will function properly in any case - it tunes for the lowest 
SWR no matter what the exact value of that SWR may be. 

Now, if the SWR = 1.0 point was not correct, that would say there may be 
a problem with the tuning.
Those wanting a more accurate SWR indication of the antenna side may 
want to consider the new Elecraft W2 as well.

73,
Don W3FPR


Wes Stewart wrote:
 I suggest a reading of Larry's original paper on the design of the LP-100 to 
 understand the heroic efforts needed to make these measurements with any 
 accuracy.

 see: http://www.telepostinc.com/Files/phipps-1.pdf

 It should come as no surprise that the K3's built-in directional coupler 
 lacks the directivity of the ones in Larry's LP-100, and directivity is 
 extremely important in this application.

 For an example left to the reader to work out, measure a load with 20 dB 
 return loss using a coupler with 20 dB directivity and see what the 
 uncertainty is.

 Wes Stewart  N7WS

   

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