Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-27 Thread Stan Gibbs

Joe,

Yes, I've been in touch with Lyle; he is trying to understand this issue and
resolve it, for which I am very grateful. Perhaps the solution will
illuminate why some observe this behavior and some do not.

Where else but Elecraft can one find such truly outstanding support?


-
73, Stan - KR7C
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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-27 Thread Gary
I must have missed something. I don't see any requirement for a sig gen in
the rf gain calibration procedure instead, I read it as being an automatic
procedure in the K3 utility that only requires a suitable load or
termination. Where is the procedure that involves a sig gen other than the
S-meter calibration that follows the rf gain calibration in the owner's
manual (pg. 51)?

I'm new to Elecraft, just built my K3 and P3 and am getting acquainted with
them.
73,
Gary
N6LRV

-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Don Wilhelm
Sent: Tuesday, October 26, 2010 8:26 AM
To: Stan Gibbs
Cc: elecraft@mailman.qth.net
Subject: Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

  Have you done as has been recommended several times during this 
thread? - use the latest K3 Utility and run the RF Gain Calibration.  
First do the set to defaults, and then run the calibration with a 
signal generator having a controlled output level.  Follow the 
instructions and be certain to tune the K3 exactly to the generators 
frequency (use CWT if necessary).

Several have commented that this step has corrected their problem.

73,
Don W3FPR


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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-27 Thread Vic K2VCO
There are two 'gain calibration' procedures. One is for TRANSMIT gain which 
requires a 
dummy load. The other is for receiver RF gain and it can be done with a signal 
source or 
by loading the factory defaults without a signal source.

It is on the Calibration page of the K3 Utility and is a button labeled 
'Calibrate RF Gain'.

On 10/27/2010 6:19 PM, Gary wrote:
 I must have missed something. I don't see any requirement for a sig gen in
 the rf gain calibration procedure instead, I read it as being an automatic
 procedure in the K3 utility that only requires a suitable load or
 termination. Where is the procedure that involves a sig gen other than the
 S-meter calibration that follows the rf gain calibration in the owner's
 manual (pg. 51)?

 I'm new to Elecraft, just built my K3 and P3 and am getting acquainted with
 them.
 73,
 Gary
 N6LRV

 -Original Message-
 From: elecraft-boun...@mailman.qth.net
 [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Don Wilhelm
 Sent: Tuesday, October 26, 2010 8:26 AM
 To: Stan Gibbs
 Cc: elecraft@mailman.qth.net
 Subject: Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

Have you done as has been recommended several times during this
 thread? - use the latest K3 Utility and run the RF Gain Calibration.
 First do the set to defaults, and then run the calibration with a
 signal generator having a controlled output level.  Follow the
 instructions and be certain to tune the K3 exactly to the generators
 frequency (use CWT if necessary).

 Several have commented that this step has corrected their problem.

 73,
 Don W3FPR

-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-26 Thread Mike
Stan, I dunno if it may be related, but I recently had a dead spot in the RF 
gain 
encoder. It was recommended that I do a recal (using 20M) with the XG2 and 
V1.3.10.15 
of the utility. An earlier version had a bug where the settings were not saved. 
Cured 
my problem.

GL  73,
Mike NF4L

 Actually, the main RX is the one giving me trouble, not the Sub; that was
 Mike's issue.  I was trying to duplicate his when I discovered mine. :-)
 The behavior of my main Rx is the same whether the Sub is enabled or not.

 I redid the RF gain calibration with my XG2 twice on 40 M and once on 20 M
 with no change in the behavior.  I would have to think that some circuit is
 not properly aligned or calibrated, but I'm not enough of a receiver expert
 enough to know which are the likely candidates.

 Thanks,

 -
 73, Stan - KR7C


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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-26 Thread Stan Gibbs


paulb wrote:
 
 Interesting to note non-linear RF gain control.
 Same thing here on the main RX.
 
Nice to know that I'm not the only one seeing this!  Thanks, Paul.

Here's some more data.  Perhaps someone can illuminate us on what it
indicates.

With my XG2 on 20m, and adjusting the main RF gain knob from full CW to full
CCW, the AFV display goes from 2329 to about 18 at the 10 o'clock position,
jumps to 1233, then declines to about 80.  The dbV display starts at +29.3
and declines to -12.4, jumps to +23.6, and then declines to -0.1 at full
CCW.

Remember that the SCN ADC results show us that the gain control is linear
in its output.

What could cause the IF gain to behave this way?  Anybody?


-
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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-26 Thread Don Wilhelm
  Have you done as has been recommended several times during this 
thread? - use the latest K3 Utility and run the RF Gain Calibration.  
First do the set to defaults, and then run the calibration with a 
signal generator having a controlled output level.  Follow the 
instructions and be certain to tune the K3 exactly to the generators 
frequency (use CWT if necessary).

Several have commented that this step has corrected their problem.

73,
Don W3FPR

On 10/26/2010 11:16 AM, Stan Gibbs wrote:

 paulb wrote:
 Interesting to note non-linear RF gain control.
 Same thing here on the main RX.

 Nice to know that I'm not the only one seeing this!  Thanks, Paul.

 Here's some more data.  Perhaps someone can illuminate us on what it
 indicates.

 With my XG2 on 20m, and adjusting the main RF gain knob from full CW to full
 CCW, the AFV display goes from 2329 to about 18 at the 10 o'clock position,
 jumps to 1233, then declines to about 80.  The dbV display starts at +29.3
 and declines to -12.4, jumps to +23.6, and then declines to -0.1 at full
 CCW.

 Remember that the SCN ADC results show us that the gain control is linear
 in its output.

 What could cause the IF gain to behave this way?  Anybody?


 -
 73, Stan - KR7C
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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-26 Thread Stan Gibbs


Don Wilhelm-4 wrote:
 
   Have you done as has been recommended several times during this 
 thread? - use the latest K3 Utility and run the RF Gain Calibration.  
 First do the set to defaults, and then run the calibration with a 
 signal generator having a controlled output level.  Follow the 
 instructions and be certain to tune the K3 exactly to the generators 
 frequency (use CWT if necessary).
 
Yes, I've repeated the calibration with my XG2 on 40 and 20 several times. 
Just to be sure there wasn't something up with the do the defaults first,
I followed your suggestion and repeated the calibration on 20m, first with
factory defaults, then with my XG2. I'm using the 1.3.10.15 K3 Utility
version.

The non-linearity is still present as before.


-
73, Stan - KR7C
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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-26 Thread hb9brj

After reading all comments, I performed an RF calibration using a -73dBm
source and the K3 Utility 1.3.10.15. First run with factory defaults, second
run using my signal source. A picture tells more than a lot of numbers:
http://home.datacomm.ch/hb9brj/RFgain.jpg

X axis = RF gain position angle in degrees: 0 = 3 o'clock, 90 = 12 o'clock,
180 = 9 o'clock
Y_left = CONFIG:SW TEST SCN ADC readout of RF gain pot
Y_right = DISP AFV in dBV

Contrary to my earlier statement my K3's main RX does show an RF gain
non-linearity.

Markus
1505
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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-26 Thread Stan Gibbs

Very nicely done, Markus!  Exactly what I observe.


-
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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-26 Thread Joe Subich, W4TV


  Contrary to my earlier statement my K3's main RX does show an RF gain
  non-linearity.

I certainly don't see any non-linearity here in either the K3 or KRX3.
Using your angle references (RG/RG$ are the RF Gain values reported
by the CAT protocol):

 --- MAIN --    KRX3 --
 RG;  ADC   dBVRG$;   ADC   dBV
   CW250  239  0   250239  0
0228  210  - 0.5   231213  - 0.1
   45182  164  - 4.2   181169  - 4.2
   90130  114  -16 132124  -17
  135 90   77  -34  91 86  -35
  180 47   46  -51  50 49  -51
  CCW  0   02  -85   0 02  -85

The compression at the top end is expected since the -73 dBm signal
is well above the AGC threshold until the RF/IF gain is reduced to
about the 12:00 (90 degree) position.

K3 s/n 1450 firmware 4.14, DSP 2.60.  Both receivers are calibrated
using the XG-2 on 20 meters with K3 Utility 1.1.10.15.

73,

... Joe, W4TV


On 10/26/2010 3:23 PM, hb9brj wrote:

 After reading all comments, I performed an RF calibration using a -73dBm
 source and the K3 Utility 1.3.10.15. First run with factory defaults, second
 run using my signal source. A picture tells more than a lot of numbers:
 http://home.datacomm.ch/hb9brj/RFgain.jpg

 X axis = RF gain position angle in degrees: 0 = 3 o'clock, 90 = 12 o'clock,
 180 = 9 o'clock
 Y_left = CONFIG:SW TEST SCN ADC readout of RF gain pot
 Y_right = DISP AFV in dBV

 Contrary to my earlier statement my K3's main RX does show an RF gain
 non-linearity.

 Markus
 1505
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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-26 Thread Stan Gibbs

Joe,

I get essentially the same numbers as you show IFF I use the factory default
calibration values.  If I use my XG2, I get the Markus curve.  Maybe my XG2
is defective?  There is some unidentified cause for this behavior, since it
is both repeatable and reproducible, and I sure would like to understand it.


-
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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-26 Thread Joe Subich, W4TV

Stan,

  If I use my XG2, I get the Markus curve.

My values are using the XG2 for calibration.

  There is some unidentified cause for this behavior, since it
  is both repeatable and reproducible, and I sure would like to
  understand it.

Lyle is apparently trying to duplicate and then find the cause
for the behavior.  It is neither repeatable nor reproducible for
me (in two K3s - 622 and 1450 and two KRX3s) and I've tried most
of the recent public beta FW/DSP releases as well.

73,

... Joe, W4TV


On 10/26/2010 10:27 PM, Stan Gibbs wrote:

 Joe,

 I get essentially the same numbers as you show IFF I use the factory default
 calibration values.  If I use my XG2, I get the Markus curve.  Maybe my XG2
 is defective?  There is some unidentified cause for this behavior, since it
 is both repeatable and reproducible, and I sure would like to understand it.


 -
 73, Stan - KR7C
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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-25 Thread Stan Gibbs


Stan Gibbs wrote:
 
 Thanks, Mike, I'll do the same measurement and see what it tells me. 
 Erratic behavior seems most likely due to a bad pot, but, as Sherlock
 would say, theorizing without data is a capital mistake.
 
Sherlock was right; it wasn't the pot.  The behavior of the voltage on its
wiper is exactly what you would expect: a smooth transition from 0V to 4.7V
for the full travel of the knob from CCW to CW.

So, the question remains, what could cause the very non-linear behavior that
I observe with the audio and S meter?

This result also renews my curiosity about whether others have observed any
non-linearity around the 10 o'clock position of the RF gain when listening
to a test signal like an XG1?

-
73, Stan - KR7C
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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-25 Thread ab2tc

Hi,

Have you tried to redo the calibration on the erratic subreceiver? It's now
been a long time since I did this, but I had to do mine three times before
it came out right. The 2 first times I had a dead zone like you do. It's
very important to make sure the frequency is spot on as the instructions
call for a very narrow bandwidth to be used.

AB2TC - Knut



Stan Gibbs wrote:
 
 
 Stan Gibbs wrote:
 
 Thanks, Mike, I'll do the same measurement and see what it tells me. 
 Erratic behavior seems most likely due to a bad pot, but, as Sherlock
 would say, theorizing without data is a capital mistake.
 
 Sherlock was right; it wasn't the pot.  The behavior of the voltage on its
 wiper is exactly what you would expect: a smooth transition from 0V to
 4.7V for the full travel of the knob from CCW to CW.
 
 So, the question remains, what could cause the very non-linear behavior
 that I observe with the audio and S meter?
 
 This result also renews my curiosity about whether others have observed
 any non-linearity around the 10 o'clock position of the RF gain when
 listening to a test signal like an XG1?
 

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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-25 Thread Stan Gibbs


ab2tc wrote:
 
 Have you tried to redo the calibration on the erratic subreceiver? It's
 now been a long time since I did this, but I had to do mine three times
 before it came out right.
 
Hi Knut,

Actually, the main RX is the one giving me trouble, not the Sub; that was
Mike's issue.  I was trying to duplicate his when I discovered mine. :-) 
The behavior of my main Rx is the same whether the Sub is enabled or not.

I redid the RF gain calibration with my XG2 twice on 40 M and once on 20 M
with no change in the behavior.  I would have to think that some circuit is
not properly aligned or calibrated, but I'm not enough of a receiver expert
enough to know which are the likely candidates.

Thanks,

-
73, Stan - KR7C
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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-25 Thread Stan Gibbs

In the process of investigating this further, I tripped over a very nice
diagnostic tool: the Config menu's SW TEST entry. This option can be set
to SCN ADC to allow monitoring of the 4 potentiometer inputs to the PIC
processor ADCs. This allows one to verify the range and linearity of the
pots very easily.

As expected, the ADC outputs produce a linear count ranging from 002 to 240
for the full travel of the pots (all 4 of them exhibit the same results). 
Those counts correspond to input voltages (from the pots) of 0.039V and
4.71V, respectively, which are essentially what I measured with my
voltmeter.

This method is MUCH easier, however, and eliminates any question as to what
the ADC is actually seeing on its inputs.


-
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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-25 Thread paulb


Hello folks

Interesting to note non-linear RF gain control.
Same thing here on the main RX.
Scn Adc check is spot on.
Approx 10o'clock position jumps to % 100.
Sub RX is ok.

cheers

Paul b
zl1ajy
3058

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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-24 Thread Guy Olinger K2AV
With no antenna attached do you see 0-3 volt range on the U3 side of
R22 on the subRX board as you vary the RF gain from min to max?  This
would be the far end of the gain process.

73, Guy

On Sun, Oct 24, 2010 at 7:48 PM, Mike Scott m...@paxsen.com wrote:
 Further to the issue that my K3 RF gain on the sub Rx won't cause the RF
 gain to go very low (I can still hear band noise and signals on the sub Rx
 at minimum gain).



 With the help of Guy I found the RF gain pots on the front panel schematic
 and understand how they might work.

 The high end of each 10K RF pot is at +5 volts, the low end is ground. The
 wiper is a voltage divider which goes to a PIC on the MCU board for decoding
 through an A-D converter on the PIC. The decoded pot voltage is then used
 later to compute RF (really IF) gain after some translation magic happens in
 the PIC and later after all the magic an analog IF gain level is created in
 a DAC to bias the RF IF amp stage. At least this is my understanding with a
 lot missing in between. It looks to me that there are HAGC1 and HAGC2 test
 points on the two RF boards. The HAGC is the hardware AGC which is derived
 from either the RF gain position Pots or H/W AGC circuitry. If I could find
 these test points and measure the 0 to 3 volts expected (0 = max gain and 3V
 = minimum gain) in the respective IF amplifiers I might learn that the sub
 RX never goes to 3V at minimum RF gain pot setting. The 0-3 volts is biasing
 a J309 IF amplifier.



 Because it might have been possible that the ground end of the Sub Rx RF pot
 was not at ground potential it was possible that the voltage signal on the
 wiper was not correct and never going to zero. This might be caused by a
 poor solder connection for example or just a faulty pot.



 The RF gain pots are accessible by removing the front bottom cover plate.
 Each of the RF-gain pot connections can be seen by inspecting the location.
 With a volt meter and tiny hook probes I measured the wiper voltage on the
 main and sub RF-gain pots at three gain settings: full on (CW), full off
 (CCW) and 12 o'clock.



 Pot         full on                   full off                  12 o'clock

 Main      4.682V                 .002V                    2.36V

 Sub         4.682V                 .002V     `              2.40V



 It looks to me like both RF-gain pots are doing exactly the right thing.



 So, now I am down to one MCU PIC A/D port is not working properly, a bad
 solder connection between the wiper arm and the PIC or Wayne is not decoding
 the two pots the same way in my serial 506 K3 or the main and sub Rx are
 treating the decoded RF gain positions differently or some other gain
 calculation is going on to modify the gain requested by the RF gain pots. I
 don't know how the variable RF gain setting is accomplished once the PIC
 decodes the pot position. Since there is no real current draw through the
 Pot I don't believe a bad solder joint is causing a partial voltage to
 arrive at the MCU PIC, it should either work or not.



 To the person who has weird main receiver RF gain action the test I did
 could help you determine if it is the Pot. As you are looking at the pot
 with the bottom front cover off put a volt meter on the middle of the three
 pot connections, the ones on the mic connector side of the pot, the other
 side of the meter to a convenient ground. You should be working with the
 most accessible or bottom-most pot. With K3 power on move the main Rx RF
 gain and check to see that voltage moves from ~5v to 0v smoothly as you turn
 the pot counter clockwise. I used mini hook grabbers to hook up the meter
 before turning power on and verified that pot resistance to ground moved
 properly when gain was moved. I didn't want to have a slip up and short
 something, this verifies I was connected to the wiper arm of the pot. You
 can't really test the full range of the pot in circuit with power off with
 an ohm meter as the high side shows something like 900 ohms resistance to
 ground with power off.



 AE6WA

 Mike Scott

 Tarzana, CA



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Re: [Elecraft] K3 Rf gain tracking (main vs. sub)

2010-10-24 Thread Stan Gibbs


Mike Scott-7 wrote:
 
 To the person who has weird main receiver RF gain action the test I did
 could help you determine if it is the Pot. 
 

Thanks, Mike, I'll do the same measurement and see what it tells me. 
Erratic behavior seems most likely due to a bad pot, but, as Sherlock would
say, theorizing without data is a capital mistake.


-
73, Stan - KR7C
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