Re: [Elecraft] KPA500 power output starts out low, then goes up

[Barthold Lichtenbelt via Elecraft]

Hi All,

Problem solved! The problem was in my K3S. A simple Transmitter Gain
calibration procedure fixed it. (This calibration you start in the K3 PC
utility). Now I am very curious to better understand why this calibration
fixed it. Also curious to know why a 6 week old K3S, built by the factory,
needed a calibration. Bad luck? Any config settings I could have done that
affect this behavior?

Many thanks to both Jack Brindle and Craig Smith from Elecraft who both
jumped on this to help me troubleshoot. Jack contacted me while he was on
vacation (!). Craig called me (!) to help me troubleshoot, just from reading
this discussion thread. The reason it took a while to fix is because I first
had to order a dummy load so I could perform the TX gain calibration
procedure. 

Jack, Craig, you guys rock!!

Barthold
AD0RM

-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of
Barthold Lichtenbelt via Elecraft
Sent: Wednesday, November 16, 2016 1:25 PM
To: 'iain macdonnell - N6ML'; 'Jack Brindle'
Cc: 'Elecraft Reflector'
Subject: Re: [Elecraft] KPA500 power output starts out low, then goes up

> I didn't see anything in this thread that suggested that the problem
wasn't observed on all bands. Maybe I missed it?

I see it on 20m, 40m, 80m, on two different antennas. Haven't tried any
other bands.

> Also haven't noticed anyone suggest using the K3's "TUNE" function,
instead of SSB modulation, as a test.

Excellent idea! It does NOT happen when I use the TUNE function. Not with
the KPA500 in standby nor in operation. Tried 20m and 40m.

> If it doesn't, it might be an issue of insufficient audio input for 
> SSB
modulation. (AFAIK) the K3 will automatically boost the audio input if it
detects that there's not enough (a feature that I'm not particularly fond
of).

I carefully tuned the Mic gain and Compression as per the manual. ALC goes
up to 5 or 6 bars, compression below 10 dB when I speak in my normal voice.
So that suggests input side is OK?

Barthold
AD0RM


-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of iain
macdonnell - N6ML
Sent: Wednesday, November 16, 2016 11:12 AM
To: Jack Brindle
Cc: Elecraft Reflector
Subject: Re: [Elecraft] KPA500 power output starts out low, then goes up

I didn't see anything in this thread that suggested that the problem wasn't
observed on all bands. Maybe I missed it?

Also haven't noticed anyone suggest using the K3's "TUNE" function, instead
of SSB modulation, as a test. If the output ramps up with the TUNE function,
it's an output problem. If it doesn't, it might be an issue of insufficient
audio input for SSB modulation. (AFAIK) the K3 will automatically boost the
audio input if it detects that there's not enough (a feature that I'm not
particularly fond of).

73,

~iain / N6ML



On Wed, Nov 16, 2016 at 9:56 AM, Jack Brindle  wrote:
> A TR switch failure would affect all bands. This one is a bit different.
It will be interesting to see the cause when we finish troubleshooting.
>
> Jack Brindle, W6FB
> Elecraft Engineering
>
> Sent from my iPhone
>
>> On Nov 16, 2016, at 12:04 PM, Arie Kleingeld PA3A  wrote:
>>
>> This might be a problem with the pin diode T/R switching in the KPA500.
>>
>>
>> 73,
>>
>> Arie
>>
>>
>>
>>
>> __
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Re: [Elecraft] KPA500 power output starts out low, then goes up

[Arie Kleingeld PA3A]

I had the KPA500 PIN diode problem in 2015, and it started on one band 
only. And it did not happen all the time. After a while it became worse 
and more bands were affected.
So based on my experience with my KPA500 #1497, I suggested the PIN 
diode problem as a possiblity.


I wonder what the serial number is of the KPA500 we are talking about, 
and whether it is produced before or after a change in the design(?). 
Anyway, when I presented this problem (how it presented itself on my 
KPA500) in the group and to elecraft support, I never got the right answer.
After basic faultfinding I found that the PIN diode circuit was causing 
the strange behaviour of the linear and then... presto... there was a 
elecraft-mod that I never heard of before.
It contained a few new switching components and some capactiors for one 
of the LP-filters.


After putting those in, problem was solved. My K3 line and me lived 
happy ever after :-).


73

Arie PA3A



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Re: [Elecraft] KPA500 power output starts out low, then goes up

[Barthold Lichtenbelt via Elecraft]

> I didn't see anything in this thread that suggested that the problem
wasn't observed on all bands. Maybe I missed it?

I see it on 20m, 40m, 80m, on two different antennas. Haven't tried any
other bands.

> Also haven't noticed anyone suggest using the K3's "TUNE" function,
instead of SSB modulation, as a test.

Excellent idea! It does NOT happen when I use the TUNE function. Not with
the KPA500 in standby nor in operation. Tried 20m and 40m.

> If it doesn't, it might be an issue of insufficient audio input for SSB
modulation. (AFAIK) the K3 will automatically boost the audio input if it
detects that there's not enough (a feature that I'm not particularly fond
of).

I carefully tuned the Mic gain and Compression as per the manual. ALC goes
up to 5 or 6 bars, compression below 10 dB when I speak in my normal voice.
So that suggests input side is OK?

Barthold
AD0RM


-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of iain
macdonnell - N6ML
Sent: Wednesday, November 16, 2016 11:12 AM
To: Jack Brindle
Cc: Elecraft Reflector
Subject: Re: [Elecraft] KPA500 power output starts out low, then goes up

I didn't see anything in this thread that suggested that the problem wasn't
observed on all bands. Maybe I missed it?

Also haven't noticed anyone suggest using the K3's "TUNE" function, instead
of SSB modulation, as a test. If the output ramps up with the TUNE function,
it's an output problem. If it doesn't, it might be an issue of insufficient
audio input for SSB modulation. (AFAIK) the K3 will automatically boost the
audio input if it detects that there's not enough (a feature that I'm not
particularly fond of).

73,

~iain / N6ML



On Wed, Nov 16, 2016 at 9:56 AM, Jack Brindle  wrote:
> A TR switch failure would affect all bands. This one is a bit different.
It will be interesting to see the cause when we finish troubleshooting.
>
> Jack Brindle, W6FB
> Elecraft Engineering
>
> Sent from my iPhone
>
>> On Nov 16, 2016, at 12:04 PM, Arie Kleingeld PA3A  wrote:
>>
>> This might be a problem with the pin diode T/R switching in the KPA500.
>>
>>
>> 73,
>>
>> Arie
>>
>>
>>
>>
>> __
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Re: [Elecraft] KPA500 power output starts out low, then goes up

[iain macdonnell - N6ML]

I didn't see anything in this thread that suggested that the problem
wasn't observed on all bands. Maybe I missed it?

Also haven't noticed anyone suggest using the K3's "TUNE" function,
instead of SSB modulation, as a test. If the output ramps up with the
TUNE function, it's an output problem. If it doesn't, it might be an
issue of insufficient audio input for SSB modulation. (AFAIK) the K3
will automatically boost the audio input if it detects that there's
not enough (a feature that I'm not particularly fond of).

73,

~iain / N6ML



On Wed, Nov 16, 2016 at 9:56 AM, Jack Brindle  wrote:
> A TR switch failure would affect all bands. This one is a bit different. It 
> will be interesting to see the cause when we finish troubleshooting.
>
> Jack Brindle, W6FB
> Elecraft Engineering
>
> Sent from my iPhone
>
>> On Nov 16, 2016, at 12:04 PM, Arie Kleingeld PA3A  wrote:
>>
>> This might be a problem with the pin diode T/R switching in the KPA500.
>>
>>
>> 73,
>>
>> Arie
>>
>>
>>
>>
>> __
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Re: [Elecraft] KPA500 power output starts out low, then goes up

[Jack Brindle]

A TR switch failure would affect all bands. This one is a bit different. It 
will be interesting to see the cause when we finish troubleshooting.

Jack Brindle, W6FB
Elecraft Engineering

Sent from my iPhone

> On Nov 16, 2016, at 12:04 PM, Arie Kleingeld PA3A  wrote:
> 
> This might be a problem with the pin diode T/R switching in the KPA500.
> 
> 
> 73,
> 
> Arie
> 
> 
> 
> 
> __
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Re: [Elecraft] KPA500 power output starts out low, then goes up

[Arie Kleingeld PA3A]

This might be a problem with the pin diode T/R switching in the KPA500.


73,

Arie




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Re: [Elecraft] KPA500 power output starts out low, then goes up

[Jack Brindle]

Several things I would suggest:

1) Turn off external ALC in the K3. We recommend NOT using it with the KPA500 
(or any other amp for that matter).

2) Run the test with the K3 connected to a power meter then a dummy load to see 
if the problem persists. If so,
you probably need to recalibrate the K3. If it does not, then we need to look 
further at the K3-KPA connection.

3) Connect the output of the KPA500 to a high-power dummy load and test. Even 
though the RigExpert may indicate
a good match, that is at very low power. At high power things can change, arcs 
may occur and other bad things may
happen. Make sure the setup works just fine into a dummy load, THEN connect to 
the antenna.

4) The KPA500 can show you voltage and current for the PA transistors. Make 
note of each as you key up the K3 to
see what is happening. They should go to fairly stable conditions fairly 
rapidly if the transmitter does the same. If
it is taking its time, then look to the transmitter for the cause.

Note that the KPA is either full on or off. It does not (nor can it) vary its 
output power in any other way. If there were 
a problem in the 15m LPF you could see a problem, but it would be persistent, 
not recovering as you indicate. So far
I am not seeing anything that indicates the problem is in the KPA. Please run 
the above suggestions. I am very
interested in the results.

73,

Jack Brindle, W6FB
Elecraft Engineering

(sent a second time trying to get the email list to accept the email...)

> On Nov 14, 2016, at 11:01 PM, Barthold Lichtenbelt via Elecraft 
>  wrote:
> 
> Thanks all for all the suggestions!
> 
> Fred Cady privately suggested making sure my ALC and Mic gain are set 
> correctly. I tuned that some more, and it is a lot better, but still doesn't 
> immediately go to full power output. 
> 
> I will test without KPA500 next.
> 
> I have two antennas, so I can test with that too, to rule out antenna 
> problems. 
> 
> As to answer your questions:
> 
>> Does the SWR also change?
> 
> Nope. Just power output. SWR graphs of my antenna are just fine (using a 
> Rigexpert AA-600 antenna analyzer).
> 
>> Have you measured the output of the K3 with a separate watt meter?
> 
> I don't have one, but both the P3TXMON and the KPA power Leds show the effect.
> 
>> How are the three boxes connected? Are you using the AuxIO cable that comes 
>> with the KPA and KAT? 
> 
> Yes, using the 15pin cables from K3S to KPA500 and KAT500. No separate key 
> line.  The P3 is connected with the RJ45 to dual serial connector cable.
> 
>> And lastly, might you have ALC enabled in the K3 menu? Anything you can tell 
>> me about the setup will be helpful.
> 
> Yes, TX ALC is ON (I never messed with that, had to look it up in the manual 
> how to get it to show up even in the config).
> 
> ALC Threshold for the KPA500 is set to 210.
> 
> The K3S has these options: Second receiver, internal tuner (Set to bypass), 
> frequency lock option, 4x 8 pole filters, DVR.
> 
> Again, thanks for the help and suggestions. Quite a friendly bunch of people 
> here!
> 
> Barthold
> AD0RM

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Re: [Elecraft] KPA500 power output starts out low, then goes up

[Barthold Lichtenbelt via Elecraft]

Thanks all for all the suggestions!

Fred Cady privately suggested making sure my ALC and Mic gain are set 
correctly. I tuned that some more, and it is a lot better, but still doesn't 
immediately go to full power output. 

I will test without KPA500 next.

I have two antennas, so I can test with that too, to rule out antenna problems. 

As to answer your questions:

> Does the SWR also change?

Nope. Just power output. SWR graphs of my antenna are just fine (using a 
Rigexpert AA-600 antenna analyzer).

> Have you measured the output of the K3 with a separate watt meter?

I don't have one, but both the P3TXMON and the KPA power Leds show the effect.

> How are the three boxes connected? Are you using the AuxIO cable that comes 
> with the KPA and KAT? 

Yes, using the 15pin cables from K3S to KPA500 and KAT500. No separate key 
line.  The P3 is connected with the RJ45 to dual serial connector cable.

> And lastly, might you have ALC enabled in the K3 menu? Anything you can tell 
> me about the setup will be helpful.

Yes, TX ALC is ON (I never messed with that, had to look it up in the manual 
how to get it to show up even in the config).

ALC Threshold for the KPA500 is set to 210.

The K3S has these options: Second receiver, internal tuner (Set to bypass), 
frequency lock option, 4x 8 pole filters, DVR.

Again, thanks for the help and suggestions. Quite a friendly bunch of people 
here!

Barthold
AD0RM

-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of ab2tc
Sent: Monday, November 14, 2016 6:22 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] KPA500 power output starts out low, then goes up

Hi,

How about following Vic, 4X6GP's advice and test the K3 without the KPA500 in 
circuit? Your symptoms are exactly as if the K3 TX calibration is badly out of 
wack as he suggests. The fact that a band change makes it worse is a dead 
give-away. A band change makes the K3's ALC algorithm reset itself to defaults 
and these defaults are set by the TX gain calibration. Your situation seems a 
bit extreme, though, with only 20% initial power so there may be other 
problems. But please test this out without the KPA500 in circuit. And surely 
eliminate antenna problems by testing into a dummy load.

AB2TC - Knut

 


Bill Conkling wrote
> That hasn’t helped my KPA500.  I notice it particularly after a band 
> change.
> 
> …bill nr4c
> 
> 
>> On Nov 13, 2016, at 10:58 PM, Vic Rosenthal 4X6GP <

> k2vco.vic@

> > wrote:
>> 
>> Hi Barthold,
>> 
>> Maybe the K3S output is ramping up slowly. Do you notice this with 
>> the
>> KPA500 off? Running the TX Gain Calibration in the K3 Utility might 
>> help in that case.
>> 
>> 73,
>> Vic, 4X6GP
>> Rehovot, Israel
>> Formerly K2VCO
>> http://www.qsl.net/k2vco/
>> 
>> On 14 Nov 2016 00:51, Barthold Lichtenbelt via Elecraft wrote:
>>> Hi All,
>>> 
>>> 
>>> 
>>> Maybe you can help with something that is baffling me. My KPA500 
>>> doesn't go to full output until I have spoken my callsign (when 
>>> trying to get through a
>>> pileup) a few times. It starts off with 100 or so watts, and after a 
>>> few iterations rises to the full 500W output. I see this both on the 
>>> KPA500 LED bar, as well as on the P3 PEP output monitored by 
>>> P3TXMON.  My full setup is
>>> K3S+KPA500+KAT500+P3+P3TXMON. All devices run the latest released
>>> firmware.
>>> 
>>> 
>>> 
>>> Any thoughts much appreciated!
>>> 
>>> 
>>> 
>>> Barthold
>>> 
>>> AD0RM
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>> email list: http://www.qsl.net/donate.html Message delivered to

> nr4c@

> 
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Re: [Elecraft] KPA500 power output starts out low, then goes up

[Bill Conkling]

just did that.  no help.

…bill
> On Nov 14, 2016, at 8:22 PM, ab2tc  wrote:
> 
> Hi,
> 
> How about following Vic, 4X6GP's advice and test the K3 without the KPA500
> in circuit? Your symptoms are exactly as if the K3 TX calibration is badly
> out of wack as he suggests. The fact that a band change makes it worse is a
> dead give-away. A band change makes the K3's ALC algorithm reset itself to
> defaults and these defaults are set by the TX gain calibration. Your
> situation seems a bit extreme, though, with only 20% initial power so there
> may be other problems. But please test this out without the KPA500 in
> circuit. And surely eliminate antenna problems by testing into a dummy load.
> 
> AB2TC - Knut
> 
> 
> 
> 
> Bill Conkling wrote
>> That hasn’t helped my KPA500.  I notice it particularly after a band
>> change.
>> 
>> …bill nr4c
>> 
>> 
>>> On Nov 13, 2016, at 10:58 PM, Vic Rosenthal 4X6GP <
> 
>> k2vco.vic@
> 
>> > wrote:
>>> 
>>> Hi Barthold,
>>> 
>>> Maybe the K3S output is ramping up slowly. Do you notice this with the
>>> KPA500 off? Running the TX Gain Calibration in the K3 Utility might help
>>> in that case.
>>> 
>>> 73,
>>> Vic, 4X6GP
>>> Rehovot, Israel
>>> Formerly K2VCO
>>> http://www.qsl.net/k2vco/
>>> 
>>> On 14 Nov 2016 00:51, Barthold Lichtenbelt via Elecraft wrote:
 Hi All,
 
 
 
 Maybe you can help with something that is baffling me. My KPA500 doesn't
 go
 to full output until I have spoken my callsign (when trying to get
 through a
 pileup) a few times. It starts off with 100 or so watts, and after a few
 iterations rises to the full 500W output. I see this both on the KPA500
 LED
 bar, as well as on the P3 PEP output monitored by P3TXMON.  My full
 setup is
 K3S+KPA500+KAT500+P3+P3TXMON. All devices run the latest released
 firmware.
 
 
 
 Any thoughts much appreciated!
 
 
 
 Barthold
 
 AD0RM
>>> __
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>>> 
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> 
>> nr4c@
> 
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> 
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Re: [Elecraft] KPA500 power output starts out low, then goes up

[ab2tc]

Hi,

How about following Vic, 4X6GP's advice and test the K3 without the KPA500
in circuit? Your symptoms are exactly as if the K3 TX calibration is badly
out of wack as he suggests. The fact that a band change makes it worse is a
dead give-away. A band change makes the K3's ALC algorithm reset itself to
defaults and these defaults are set by the TX gain calibration. Your
situation seems a bit extreme, though, with only 20% initial power so there
may be other problems. But please test this out without the KPA500 in
circuit. And surely eliminate antenna problems by testing into a dummy load.

AB2TC - Knut

 


Bill Conkling wrote
> That hasn’t helped my KPA500.  I notice it particularly after a band
> change.
> 
> …bill nr4c
> 
> 
>> On Nov 13, 2016, at 10:58 PM, Vic Rosenthal 4X6GP <

> k2vco.vic@

> > wrote:
>> 
>> Hi Barthold,
>> 
>> Maybe the K3S output is ramping up slowly. Do you notice this with the
>> KPA500 off? Running the TX Gain Calibration in the K3 Utility might help
>> in that case.
>> 
>> 73,
>> Vic, 4X6GP
>> Rehovot, Israel
>> Formerly K2VCO
>> http://www.qsl.net/k2vco/
>> 
>> On 14 Nov 2016 00:51, Barthold Lichtenbelt via Elecraft wrote:
>>> Hi All,
>>> 
>>> 
>>> 
>>> Maybe you can help with something that is baffling me. My KPA500 doesn't
>>> go
>>> to full output until I have spoken my callsign (when trying to get
>>> through a
>>> pileup) a few times. It starts off with 100 or so watts, and after a few
>>> iterations rises to the full 500W output. I see this both on the KPA500
>>> LED
>>> bar, as well as on the P3 PEP output monitored by P3TXMON.  My full
>>> setup is
>>> K3S+KPA500+KAT500+P3+P3TXMON. All devices run the latest released
>>> firmware.
>>> 
>>> 
>>> 
>>> Any thoughts much appreciated!
>>> 
>>> 
>>> 
>>> Barthold
>>> 
>>> AD0RM
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Re: [Elecraft] KPA500 power output starts out low, then goes up

[Bill Conkling]

That hasn’t helped my KPA500.  I notice it particularly after a band change.

…bill nr4c


> On Nov 13, 2016, at 10:58 PM, Vic Rosenthal 4X6GP  wrote:
> 
> Hi Barthold,
> 
> Maybe the K3S output is ramping up slowly. Do you notice this with the KPA500 
> off? Running the TX Gain Calibration in the K3 Utility might help in that 
> case.
> 
> 73,
> Vic, 4X6GP
> Rehovot, Israel
> Formerly K2VCO
> http://www.qsl.net/k2vco/
> 
> On 14 Nov 2016 00:51, Barthold Lichtenbelt via Elecraft wrote:
>> Hi All,
>> 
>> 
>> 
>> Maybe you can help with something that is baffling me. My KPA500 doesn't go
>> to full output until I have spoken my callsign (when trying to get through a
>> pileup) a few times. It starts off with 100 or so watts, and after a few
>> iterations rises to the full 500W output. I see this both on the KPA500 LED
>> bar, as well as on the P3 PEP output monitored by P3TXMON.  My full setup is
>> K3S+KPA500+KAT500+P3+P3TXMON. All devices run the latest released firmware.
>> 
>> 
>> 
>> Any thoughts much appreciated!
>> 
>> 
>> 
>> Barthold
>> 
>> AD0RM
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Re: [Elecraft] KPA500 power output starts out low, then goes up

[Vic Rosenthal 4X6GP]

Hi Barthold,

Maybe the K3S output is ramping up slowly. Do you notice this with the 
KPA500 off? Running the TX Gain Calibration in the K3 Utility might help 
in that case.


73,
Vic, 4X6GP
Rehovot, Israel
Formerly K2VCO
http://www.qsl.net/k2vco/

On 14 Nov 2016 00:51, Barthold Lichtenbelt via Elecraft wrote:

Hi All,



Maybe you can help with something that is baffling me. My KPA500 doesn't go
to full output until I have spoken my callsign (when trying to get through a
pileup) a few times. It starts off with 100 or so watts, and after a few
iterations rises to the full 500W output. I see this both on the KPA500 LED
bar, as well as on the P3 PEP output monitored by P3TXMON.  My full setup is
K3S+KPA500+KAT500+P3+P3TXMON. All devices run the latest released firmware.



Any thoughts much appreciated!



Barthold

AD0RM

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