Power variations in K3 / 3.19

[Ignacy]

After lengthy QSOs and after slight retuning, power from K3 drops to about 1-2W and the radio draws about 3A. It is still set to 110W and cranking the power down and back does not change anything. Same after QSY to another band. PA temp shows 35C. A few minutes later the power is back. This problem is new and may be peculiar to 3.19.

There is an old problem still present on 3.19. AFter turning the rig on, in SSB the peak power starts at 30-70W and in a minute of transmitting rises to about 95W (when set to 110W). Measurements with LP-100 calibrated in factory.  The initial power varies from time to time.

Any ideas?

Ignacy

[ab2tc]

I have this problem also, not only after power up, but after each band change. My favorite workaround is to change mode to data FSK, switch to dummy load, then press PTT  for a couple of seconds. Back to SSB and I have full talk power immediately.

Can't comment on your other problem as I am still on 3.14.

Knut - AB2TC

Ignacy wrote

<snip>

There is an old problem still present on 3.19. AFter turning the rig on, in SSB the peak power starts at 30-70W and in a minute of transmitting rises to about 95W (when set to 110W). Measurements with LP-100 calibrated in factory.  The initial power varies from time to time.

Any ideas?

Ignacy

[Vic Goncharsky]

I have noticed this problem after assembling K3 of mine. Asked Lyle about it in Dayton. He recommended a few things which did not help in my case, the rising SSB power syndrome is still there. Looks like a slow RC-chain somewhere in the power control circuitry. It's just my assumption, which can be a wrong one.73, Vic US5WE/K1WEK3 #2907 

--- On Thu, 7/9/09, ab2tc <[hidden email]> wrote:

From: ab2tc <[hidden email]>
Subject: Re: [Elecraft] [K3]  Power variations in K3 / 3.19
To: [hidden email]
Date: Thursday, July 9, 2009, 2:35 PM


I have this problem also, not only after power up, but after each band
change. My favorite workaround is to change mode to data FSK, switch to
dummy load, then press PTT  for a couple of seconds. Back to SSB and I have
full talk power immediately.

Can't comment on your other problem as I am still on 3.14.

Knut - AB2TC

Ignacy wrote:

>
> <snip>
>
> There is an old problem still present on 3.19. AFter turning the rig on,
> in SSB the peak power starts at 30-70W and in a minute of transmitting
> rises to about 95W (when set to 110W). Measurements with LP-100 calibrated
> in factory.  The initial power varies from time to time.
>
> Any ideas?
>
> Ignacy
>
>
>
>
>
>
>
>
>

-----
AB2TC - Knut
--
View this message in context: http://n2.nabble.com/Power-variations-in-K3---3.19-tp3231601p3231790.html
Sent from the [K3] mailing list archive at Nabble.com.
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[Greg VK3VT]

I suggest that you make sure that you have run the "Calibrate
Transmitter gain "  in the configuration section of the Elecraft K3
Utility.  That fixed an issue I had that was similar to yours.

Greg VK3VT

Subject:
Re: [Elecraft] [K3] Power variations in K3 / 3.19
From:
ab2tc <[hidden email]>
Date:
Thu, 9 Jul 2009 07:35:09 -0700 (PDT)

To:
[hidden email]


I have this problem also, not only after power up, but after each band
change. My favorite workaround is to change mode to data FSK, switch to
dummy load, then press PTT  for a couple of seconds. Back to SSB and I have
full talk power immediately.


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[AB3EN]

I also had issues with this issue and Wayne suggested that I look at my TXG VCE setting and move it to 1.0 ~2.0 db I have mine set to 2.0 and it seems to help.

73Dan AB3EN

Greg Williams-4 wrote

I suggest that you make sure that you have run the "Calibrate
Transmitter gain "  in the configuration section of the Elecraft K3
Utility.  That fixed an issue I had that was similar to yours.

Greg VK3VT

Subject:
Re: [Elecraft] [K3] Power variations in K3 / 3.19
From:
ab2tc <[e-mail]>
Date:
Thu, 9 Jul 2009 07:35:09 -0700 (PDT)

To:
[e-mail]


I have this problem also, not only after power up, but after each band
change. My favorite workaround is to change mode to data FSK, switch to
dummy load, then press PTT  for a couple of seconds. Back to SSB and I have
full talk power immediately.


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[Bjorn]

On 9 jul 2009, at 16.02, Ignacy wrote:

> There is an old problem still present on 3.19. AFter turning the rig  
> on, in
> SSB the peak power starts at 30-70W and in a minute of transmitting  
> rises to
> about 95W (when set to 110W). Measurements with LP-100 calibrated in
> factory.  The initial power varies from time to time.
>
> Any ideas?

This problem has been around for some time with my K3. What happens  
for me is that when I set the power to specific level and push TUNE  
the radio stabilizes at that preset level. Then when keying and begin  
talking the power level is a lot lower that verified with TUNE. After  
a few seconds the power peaks are in the vicinity of the preset level,  
but sometimes peaks are reaching above the preset level which makes me  
reluctant to mess with TXG VCE. Another observation is that this  
problem is only with the PA in line, taking power below 12 watts seems  
to eliminate the issue.

Earlier the problem was reversed as power overshot the set level in  
SSB, now I am less worried but seeing the issue solved would provide  
some comfort when using the amp.

I am also using a factory calibrated LP-100A to verify my measurements.


73 de Björn,
SM0MDG
SE0X

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[wayne burdick]

I'll be reviewing power-settling behavior  when I get a chance. Thanks  
for the report.

73,
Wayne, N6KR

Sent from my iPhone

On Jul 18, 2009, at 8:38 AM, Björn Mohr <[hidden email]> wrote:

> On 9 jul 2009, at 16.02, Ignacy wrote:
>
>> There is an old problem still present on 3.19. AFter turning the  
>> rig on, in
>> SSB the peak power starts at 30-70W and in a minute of transmitting  
>> rises to
>> about 95W (when set to 110W). Measurements with LP-100 calibrated in
>> factory.  The initial power varies from time to time.
>>
>> Any ideas?
>
> This problem has been around for some time with my K3. What happens  
> for me is that when I set the power to specific level and push TUNE  
> the radio stabilizes at that preset level. Then when keying and  
> begin talking the power level is a lot lower that verified with  
> TUNE. After a few seconds the power peaks are in the vicinity of the  
> preset level, but sometimes peaks are reaching above the preset  
> level which makes me reluctant to mess with TXG VCE. Another  
> observation is that this problem is only with the PA in line, taking  
> power below 12 watts seems to eliminate the issue.
>
> Earlier the problem was reversed as power overshot the set level in  
> SSB, now I am less worried but seeing the issue solved would provide  
> some comfort when using the amp.
>
> I am also using a factory calibrated LP-100A to verify my  
> measurements.
>
>
> 73 de Björn,
> SM0MDG
> SE0X

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[K2QI]

Björn's description of the KPA3 behavior sounds incredibly similar to issues
I've been experiencing when only operating in sideband.  My problem however
isn't so much of an initial low power transmit, but what appears to be the
complete opposite.  Some of you may recall the post I submitted to the
reflector several days ago about strange RF activity and my K3.  In a
nutshell, my SWR alarm on my wattmeter will trip upon initial keydown when
operating in sideband and the linear is on.  It functions fine on the other
hand if I key down with a continuous carrier.. even up to 1200W.  The
exciter drive level doesn't seem to make too much of a difference UNLESS I
turn the power output to 12W or less.  The moment I switch back to 13W or
higher and the KPA3 is in line, the problems begin.  Looking at my wattmeter
in peak mode shows an initial burst of power when keying down.  After a few
seconds, the power drops back to a normal level.  I have a theory that
there's some sort of RF burst in sideband mode upon initial keydown; perhaps
the KPA3 oscillates for just a few seconds and transmits off-frequency until
it stabilizes.  This is just a theory though.

I'm still playing with my RF grounding and isolation to fully hope in
eliminating all other possibilities before pointing the finger at the K3.

73 de James K2QI


2009/7/18 Björn Mohr [hidden email]

>
> This problem has been around for some time with my K3. What happens
> for me is that when I set the power to specific level and push TUNE
> the radio stabilizes at that preset level. Then when keying and begin
> talking the power level is a lot lower that verified with TUNE. After
> a few seconds the power peaks are in the vicinity of the preset level,
> but sometimes peaks are reaching above the preset level which makes me
> reluctant to mess with TXG VCE. Another observation is that this
> problem is only with the PA in line, taking power below 12 watts seems
> to eliminate the issue.
>
> Earlier the problem was reversed as power overshot the set level in
> SSB, now I am less worried but seeing the issue solved would provide
> some comfort when using the amp.
>
> I am also using a factory calibrated LP-100A to verify my measurements.
>
>
> 73 de Björn,
> SM0MDG
> SE0X
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>

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[myles landstein]

sorry your still having trouble

Can't say for sure   but could very well be  some  funky grounding.

check  it into a dummy load  to at least  eliminate  the antenna  System

If you can  also  try to   vary the length of the coax going from the  
rig to  amp (sometimes helps)

using a speech compressor?

measure  your  grounds  and  any external power supplies used  for  
ac  leaking  over  , maybe a long shot easy to check w/vom



goodluck
N2EHG

On Jul 18, 2009, at 11:28 AM, K2QI wrote:

> Björn's description of the KPA3 behavior sounds incredibly similar  
> to issues
> I've been experiencing when only operating in sideband.  My problem  
> however
> isn't so much of an initial low power transmit, but what appears to  
> be the
> complete opposite.  Some of you may recall the post I submitted to the
> reflector several days ago about strange RF activity and my K3.  In a
> nutshell, my SWR alarm on my wattmeter will trip upon initial  
> keydown when
> operating in sideband and the linear is on.  It functions fine on  
> the other
> hand if I key down with a continuous carrier.. even up to 1200W.  The
> exciter drive level doesn't seem to make too much of a difference  
> UNLESS I
> turn the power output to 12W or less.  The moment I switch back to  
> 13W or
> higher and the KPA3 is in line, the problems begin.  Looking at my  
> wattmeter
> in peak mode shows an initial burst of power when keying down.  
> After a few
> seconds, the power drops back to a normal level.  I have a theory that
> there's some sort of RF burst in sideband mode upon initial keydown;  
> perhaps
> the KPA3 oscillates for just a few seconds and transmits off-
> frequency until
> it stabilizes.  This is just a theory though.
>
> I'm still playing with my RF grounding and isolation to fully hope in
> eliminating all other possibilities before pointing the finger at  
> the K3.
>
> 73 de James K2QI
>
>
> 2009/7/18 Björn Mohr [hidden email]
>
>>
>> This problem has been around for some time with my K3. What happens
>> for me is that when I set the power to specific level and push TUNE
>> the radio stabilizes at that preset level. Then when keying and begin
>> talking the power level is a lot lower that verified with TUNE. After
>> a few seconds the power peaks are in the vicinity of the preset  
>> level,
>> but sometimes peaks are reaching above the preset level which makes  
>> me
>> reluctant to mess with TXG VCE. Another observation is that this
>> problem is only with the PA in line, taking power below 12 watts  
>> seems
>> to eliminate the issue.
>>
>> Earlier the problem was reversed as power overshot the set level in
>> SSB, now I am less worried but seeing the issue solved would provide
>> some comfort when using the amp.
>>
>> I am also using a factory calibrated LP-100A to verify my  
>> measurements.
>>
>>
>> 73 de Björn,
>> SM0MDG
>> SE0X
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
> ______________________________________________________________
> Elecraft mailing list
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> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

Myles Landstein
[hidden email]
please note my   new email address
dti will soon be eliminated , gmail is my new home  update your dir

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[K2QI]

Wayne,

Could it be possible that the KPA3 upon initial key-down in sideband could
be oscillating for a second or two out of frequency?  If that's the case,
this could explain Bjorn's low-power out issue along with my SWR
alarm-tripping problem.  I've noticed that when my meter is set to peak
mode, when I key the microphone without talking, I'll see a burst of power
along with an increase in SWR for 1 or 2 seconds before it settles.  This
only occurs in sideband and not in any other constant carrier mode.

73 de James K2QI


-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Wayne Burdick
Sent: Saturday, July 18, 2009 9:59 AM
To: Björn Mohr
Cc: [hidden email]; Ignacy
Subject: Re: [Elecraft] [K3] Power variations in K3 / 3.19

I'll be reviewing power-settling behavior  when I get a chance. Thanks  
for the report.

73,
Wayne, N6KR


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[Guy, K2AV]

Roughly speaking, if one is talking about the impedance looking into a
typical grounded grid linear amp, the driving impedance begins to vary
considerably as the driving signal negative peak voltage lessens approaching
the tube's grid cutoff voltage plus cathode bias, and a larger and larger
percentage of the drive cycle is in the tube conduction range.  This is more
obvious on SSB if the amp has a higher cathode bias value for CW.

The input network for the amp is generally tuned to match power and
conduction cycles when driving the amp to full output.

73, Guy
2009/7/18 K2QI <[hidden email]>

> Björn's description of the KPA3 behavior sounds incredibly similar to
> issues
> I've been experiencing when only operating in sideband.  My problem however
> isn't so much of an initial low power transmit, but what appears to be the
> complete opposite.  Some of you may recall the post I submitted to the
> reflector several days ago about strange RF activity and my K3.  In a
> nutshell, my SWR alarm on my wattmeter will trip upon initial keydown when
> operating in sideband and the linear is on.  It functions fine on the other
> hand if I key down with a continuous carrier.. even up to 1200W.  The
> exciter drive level doesn't seem to make too much of a difference UNLESS I
> turn the power output to 12W or less.  The moment I switch back to 13W or
> higher and the KPA3 is in line, the problems begin.  Looking at my
> wattmeter
> in peak mode shows an initial burst of power when keying down.  After a few
> seconds, the power drops back to a normal level.  I have a theory that
> there's some sort of RF burst in sideband mode upon initial keydown;
> perhaps
> the KPA3 oscillates for just a few seconds and transmits off-frequency
> until
> it stabilizes.  This is just a theory though.
>
> I'm still playing with my RF grounding and isolation to fully hope in
> eliminating all other possibilities before pointing the finger at the K3.
>
> 73 de James K2QI
>
>

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