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K2 KPA/100 excessive power issue, SSB mode, some bands

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Ken Cannaday

K2 KPA/100 excessive power issue, SSB mode, some bands

I had an RF feedback problem on 40 meter SSB, which I brought under control,
mainly by winding a foot or two of mike cable through a ferrite core.

However, I had been having another problem on 40 meters SSB that had gone
unnoticed until the power supply (rated at 30 amp surge) tripped out on a
voice peak.
Power control seemed okay because the output as measured on the meter in my
MFJ tuner was the same as the power setting on the K2 in Tune, Tune +
Display (override 20 watt limit), and CW modes.

However, on SSB, the circumsatance was very different. If the setting was
for 100 watts, the meter in the tuner would often kick up to 100 watts or
more on voice peaks, whereas with my Icom transceivers, it generally will
not kick
any higher than half the power setting (i.e. 50 watts). (I really have no
good way of accurately measuring peak power on SSB and always assumed PEP
would be the same as the output in continuous carrier mode.) Turns out that
on 40
and 30 meters, and to a lesser extent on 80, while transmitting into a dummy
load, I apparently get two to four times the expected power on voice
peaks, judging by the meter in the tuner (and applying the times two
formula). This only occurs when the KPA/100 is active. It does not occur
with the basic K2 in QRP mode. Moreover, even with KPA/100 active, if I set
compression (SSBC) and audio (SSBA) to the lowest levels, the power reading
levels appear to be similar to the Icom - about 50% of nominal power on
voice peaks.

My KPA/100 is revision C and does not have the KPA100UPKT installed. Does
anyone have any suggestions for this problem? Would the KPA100UPKT likely
solve the problem? On the other hand, would there be any harm in setting
the
power levels and/or the SSBA and SSBC parameters so that output does not
exceed
100 watts, and continuing to operate with the KPA100 as is?

Any help would be greatly appreciated!

Ken, W4NZC

73!

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Don Wilhelm-4

Re: K2 KPA/100 excessive power issue, SSB mode, some bands

Ken,

That description sounds suspiciously like you are developing a parasitic
on 40 meters.
Yes, the first step in getting that under control is to install the
KPA100UPKT.
It was developed specifically to address a problem very similar to yours.

There is another possibility (since you mentioned the SSBA and SSBC
parameters) - that you are driving the mic input too hard. switch the
display to read ALC. You should have no more than 3 bars with maybe an
occasional 4th.
There should be no problem with an SSBC setting of 3:1 or even 4:1, but
the SSBA parameter will depend on your mic. If you are using the
Elecraft mics, set SSBA to 1.

73,
Don W3FPR

On 8/27/2010 11:42 AM, Ken Cannaday wrote:

> I had an RF feedback problem on 40 meter SSB, which I brought under control,
> mainly by winding a foot or two of mike cable through a ferrite core.
>
> However, I had been having another problem on 40 meters SSB that had gone
> unnoticed until the power supply (rated at 30 amp surge) tripped out on a
> voice peak.
> Power control seemed okay because the output as measured on the meter in my
> MFJ tuner was the same as the power setting on the K2 in Tune, Tune +
> Display (override 20 watt limit), and CW modes.
>
> However, on SSB, the circumsatance was very different. If the setting was
> for 100 watts, the meter in the tuner would often kick up to 100 watts or
> more on voice peaks, whereas with my Icom transceivers, it generally will
> not kick
> any higher than half the power setting (i.e. 50 watts). (I really have no
> good way of accurately measuring peak power on SSB and always assumed PEP
> would be the same as the output in continuous carrier mode.) Turns out that
> on 40
> and 30 meters, and to a lesser extent on 80, while transmitting into a dummy
> load, I apparently get two to four times the expected power on voice
> peaks, judging by the meter in the tuner (and applying the times two
> formula). This only occurs when the KPA/100 is active. It does not occur
> with the basic K2 in QRP mode. Moreover, even with KPA/100 active, if I set
> compression (SSBC) and audio (SSBA) to the lowest levels, the power reading
> levels appear to be similar to the Icom - about 50% of nominal power on
> voice peaks.
>
> My KPA/100 is revision C and does not have the KPA100UPKT installed. Does
> anyone have any suggestions for this problem? Would the KPA100UPKT likely
> solve the problem? On the other hand, would there be any harm in setting
> the
> power levels and/or the SSBA and SSBC parameters so that output does not
> exceed
> 100 watts, and continuing to operate with the KPA100 as is?
>
> Any help would be greatly appreciated!
>
> Ken, W4NZC
>
> 73!
>
> ______________________________________________________________
> 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
>

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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Bob Naumann W5OV

Re: K2 KPA/100 excessive power issue, SSB mode, some bands

In reply to this post by Ken Cannaday

Have you tried a different power supply?

I have seen many power supplies that are sensitive to 40m RF and trip out
as you describe.

Since you already know you have 40m RF in the shack, perhaps this is a
much simpler problem to resolve?

73,

W5OV

> I had an RF feedback problem on 40 meter SSB, which I brought under
> control,
> mainly by winding a foot or two of mike cable through a ferrite core.
>
> However, I had been having another problem on 40 meters SSB that had gone
> unnoticed until the power supply (rated at 30 amp surge) tripped out on a
> voice peak.
> Power control seemed okay because the output as measured on the meter in
> my
> MFJ tuner was the same as the power setting on the K2 in Tune, Tune +
> Display (override 20 watt limit), and CW modes.
>
> However, on SSB, the circumsatance was very different. If the setting was
> for 100 watts, the meter in the tuner would often kick up to 100 watts or
> more on voice peaks, whereas with my Icom transceivers, it generally will
> not kick
> any higher than half the power setting (i.e. 50 watts). (I really have no
> good way of accurately measuring peak power on SSB and always assumed PEP
> would be the same as the output in continuous carrier mode.) Turns out
> that
> on 40
> and 30 meters, and to a lesser extent on 80, while transmitting into a
> dummy
> load, I apparently get two to four times the expected power on voice
> peaks, judging by the meter in the tuner (and applying the times two
> formula). This only occurs when the KPA/100 is active. It does not occur
> with the basic K2 in QRP mode. Moreover, even with KPA/100 active, if I
> set
> compression (SSBC) and audio (SSBA) to the lowest levels, the power
> reading
> levels appear to be similar to the Icom - about 50% of nominal power on
> voice peaks.
>
> My KPA/100 is revision C and does not have the KPA100UPKT installed. Does
> anyone have any suggestions for this problem? Would the KPA100UPKT likely
> solve the problem? On the other hand, would there be any harm in setting
> the
> power levels and/or the SSBA and SSBC parameters so that output does not
> exceed
> 100 watts, and continuing to operate with the KPA100 as is?
>
> Any help would be greatly appreciated!
>
> Ken, W4NZC
>
> 73!
>
> ______________________________________________________________
> 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
>

Steve Kavanagh

Re: K2 KPA/100 excessive power issue, SSB mode, some bands

In reply to this post by Ken Cannaday

Ken:

The excessive power could also be due to a problem some of us have had where the KPA100 gain is high enough that the ALC circuits do not have enough range to control the power on some bands (typically 80m and/or 40m). Only SSB is affected, not CW.

See:

http://mailman.qth.net/pipermail/elecraft/2005-December/050672.html

for my symptoms, and

http://mailman.qth.net/pipermail/elecraft/2005-December/050967.html

for a short summary of the cure in my K2.

Try to see what happens on a dummy load...if you still have the problem that would rule out RF feedback. My transmitted signal was quite distorted on SSB...an on air signal quality report might help you determine the source of the problem, too.

73,
Steve VE3SMA

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Ken Cannaday

Re: K2 KPA/100 excessive power issue, SSB mode, some bands

In reply to this post by Don Wilhelm-4

Thanks much for the comments, all were very helpful and are much
appreciated. I did some further testing along the lines suggested with the
following results:

Settings: SSBA = 1; SSBC = 3 to 1; requested power QRP = 2, QRO = 20;
transmitting into a dummy load; microphone = Heil HC4 (but similar results
have generally been experienced with Icom electret hand mike, HM 36); all
bands tested in both TUNE and SSB modes .

Generally in QRP on TUNE mode, I saw anywhere from 2.8 to 2.3 watts after
the ALC had time to settle in (the ALC seems to start over with any change
in band or certain other settings). In particular, I saw 2.8 watts on 160,
2.3 on 10 meters, with the other bands somewhere in between. In SSB, I
generally saw peaks at one or two bars, with an occasional third bar, for
ALC; and two bars with an occasional third bar for RF. The exceptions were:
80 meters, where there was a very brief initial surge up to 4 or 5 bars
before settling in at 1 to 3 bars for ALC, and 2 to 3 bars for RF; 40
meters, where again there was the initial surge in reading before settling
at 3 to 4 bars for both ALC and RF; 30 meters where the results were similar
to 40 meters except that RF eventually settled to only 2 to 3 bars.

Then switching to QRO, on Tune mode, I saw 19, 20, or 21 watts on all bands
except on 80 meters where the ALC never seemed to settle in and kept
bouncing around between 18 and 22 watts, with 19 being the most stabile
eventual reading. In SSB, I generally saw peaks at 1 (10 and 12 meters), 1
to 2, or 2 to 3 (160) bars for ALC and 2 to 3 bars for RF. On 80 meters,
however, there was again an initial surge, lasting a little longer and
settling in a little slower to an eventual 2 to 3 bars for ALC and a solid 3
bars of RF; on 40 the initial surge was more extreme with the ALC kicking up
as high as 6 bars before settling in at 3 to 4 bars, 2 to 3 bars for RF.
The most extreme results were on 30 meters where I saw readings as high as 5
to 6 bars for ALC and 7 to 10 bars for RF. After a much longer period of
speaking into the microphone, eventually readings settled respectively to 3
to 4 bars with a rare 5th bar and 2 to 3 bars with an occasional 4th bar.

I should add that I can generally get a bit higher readings by screaming
into the microphone, but the results summarized above were obtained by
speaking just a bit louder than normal, as if I am excited on the verge of
working a new, rare DX entity.

Generally a higher RF reading was supported by a higher ALC reading. Does
this indicate that any excess in power output is not likely to be an ALC
problem rather than a KPA/100 problem? How necessary do you think it is to
install the KPA100UPKT given these results? Any observations or suggestions
would be appreciated.

73

Ken

----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Ken Cannaday" <[hidden email]>
Cc: <[hidden email]>
Sent: Friday, August 27, 2010 12:00 PM
Subject: Re: [Elecraft] K2 KPA/100 excessive power issue, SSB mode, some
bands

> Ken,
>
> That description sounds suspiciously like you are developing a parasitic
> on 40 meters.
> Yes, the first step in getting that under control is to install the
> KPA100UPKT.
> It was developed specifically to address a problem very similar to yours.
>
> There is another possibility (since you mentioned the SSBA and SSBC
> parameters) - that you are driving the mic input too hard. switch the
> display to read ALC. You should have no more than 3 bars with maybe an
> occasional 4th.
> There should be no problem with an SSBC setting of 3:1 or even 4:1, but
> the SSBA parameter will depend on your mic. If you are using the Elecraft
> mics, set SSBA to 1.
>
> 73,
> Don W3FPR
>
> On 8/27/2010 11:42 AM, Ken Cannaday wrote:
>> I had an RF feedback problem on 40 meter SSB, which I brought under
>> control,
>> mainly by winding a foot or two of mike cable through a ferrite core.
>>
>> However, I had been having another problem on 40 meters SSB that had gone
>> unnoticed until the power supply (rated at 30 amp surge) tripped out on a
>> voice peak.
>> Power control seemed okay because the output as measured on the meter in
>> my
>> MFJ tuner was the same as the power setting on the K2 in Tune, Tune +
>> Display (override 20 watt limit), and CW modes.
>>
>> However, on SSB, the circumsatance was very different. If the setting
>> was
>> for 100 watts, the meter in the tuner would often kick up to 100 watts or
>> more on voice peaks, whereas with my Icom transceivers, it generally will
>> not kick
>> any higher than half the power setting (i.e. 50 watts). (I really have
>> no
>> good way of accurately measuring peak power on SSB and always assumed PEP
>> would be the same as the output in continuous carrier mode.) Turns out
>> that
>> on 40
>> and 30 meters, and to a lesser extent on 80, while transmitting into a
>> dummy
>> load, I apparently get two to four times the expected power on voice
>> peaks, judging by the meter in the tuner (and applying the times two
>> formula). This only occurs when the KPA/100 is active. It does not
>> occur
>> with the basic K2 in QRP mode. Moreover, even with KPA/100 active, if I
>> set
>> compression (SSBC) and audio (SSBA) to the lowest levels, the power
>> reading
>> levels appear to be similar to the Icom - about 50% of nominal power on
>> voice peaks.
>>
>> My KPA/100 is revision C and does not have the KPA100UPKT installed.
>> Does
>> anyone have any suggestions for this problem? Would the KPA100UPKT
>> likely
>> solve the problem? On the other hand, would there be any harm in setting
>> the
>> power levels and/or the SSBA and SSBC parameters so that output does not
>> exceed
>> 100 watts, and continuing to operate with the KPA100 as is?
>>
>> Any help would be greatly appreciated!
>>
>> Ken, W4NZC
>>
>> 73!
>>
>> ______________________________________________________________
>> 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
>>

Don Wilhelm-4

Re: K2 KPA/100 excessive power issue, SSB mode, some bands

Ken,

This is behavior that is typical after the KI6WX SSB RF Gain mod has
been installed.
Whether or not you have installed that mod, try the following changes to
the KSB2 board:
1 - Change R9 to 15k
2 - Cut the trace (on the top of the board) between P1 pin 6 and the
base of Q1 and insert a 1k resistor between those two points. You will
have to orient the resistor vertically, or use an SMD resistor.

That should calm the ALC overshoot when operating into a dummy load.

The question still remains about the original problem which was an
overshoot problem on 40 meters. If that persists when operating into an
antenna, the KPA100UPKT is the solution.

73,
Don W3FPR

On 8/31/2010 6:54 AM, Ken Cannaday wrote:

> Thanks much for the comments, all were very helpful and are much
> appreciated. I did some further testing along the lines suggested with the
> following results:
>
> Settings: SSBA = 1; SSBC = 3 to 1; requested power QRP = 2, QRO = 20;
> transmitting into a dummy load; microphone = Heil HC4 (but similar results
> have generally been experienced with Icom electret hand mike, HM 36); all
> bands tested in both TUNE and SSB modes .
>
> Generally in QRP on TUNE mode, I saw anywhere from 2.8 to 2.3 watts after
> the ALC had time to settle in (the ALC seems to start over with any change
> in band or certain other settings). In particular, I saw 2.8 watts on 160,
> 2.3 on 10 meters, with the other bands somewhere in between. In SSB, I
> generally saw peaks at one or two bars, with an occasional third bar, for
> ALC; and two bars with an occasional third bar for RF. The exceptions were:
> 80 meters, where there was a very brief initial surge up to 4 or 5 bars
> before settling in at 1 to 3 bars for ALC, and 2 to 3 bars for RF; 40
> meters, where again there was the initial surge in reading before settling
> at 3 to 4 bars for both ALC and RF; 30 meters where the results were similar
> to 40 meters except that RF eventually settled to only 2 to 3 bars.
>
> Then switching to QRO, on Tune mode, I saw 19, 20, or 21 watts on all bands
> except on 80 meters where the ALC never seemed to settle in and kept
> bouncing around between 18 and 22 watts, with 19 being the most stabile
> eventual reading. In SSB, I generally saw peaks at 1 (10 and 12 meters), 1
> to 2, or 2 to 3 (160) bars for ALC and 2 to 3 bars for RF. On 80 meters,
> however, there was again an initial surge, lasting a little longer and
> settling in a little slower to an eventual 2 to 3 bars for ALC and a solid 3
> bars of RF; on 40 the initial surge was more extreme with the ALC kicking up
> as high as 6 bars before settling in at 3 to 4 bars, 2 to 3 bars for RF.
> The most extreme results were on 30 meters where I saw readings as high as 5
> to 6 bars for ALC and 7 to 10 bars for RF. After a much longer period of
> speaking into the microphone, eventually readings settled respectively to 3
> to 4 bars with a rare 5th bar and 2 to 3 bars with an occasional 4th bar.
>
> I should add that I can generally get a bit higher readings by screaming
> into the microphone, but the results summarized above were obtained by
> speaking just a bit louder than normal, as if I am excited on the verge of
> working a new, rare DX entity.
>
> Generally a higher RF reading was supported by a higher ALC reading. Does
> this indicate that any excess in power output is not likely to be an ALC
> problem rather than a KPA/100 problem? How necessary do you think it is to
> install the KPA100UPKT given these results? Any observations or suggestions
> would be appreciated.
>
> 73
>
> Ken
>

Ken Cannaday

Re: K2 KPA/100 excessive power issue, SSB mode, some bands

I will give it a try, thanks again for all the help! Ken

----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Ken Cannaday" <[hidden email]>
Cc: <[hidden email]>
Sent: Tuesday, August 31, 2010 9:11 AM
Subject: Re: [Elecraft] K2 KPA/100 excessive power issue, SSB mode, some
bands

> Ken,
>
> This is behavior that is typical after the KI6WX SSB RF Gain mod has been
> installed.
> Whether or not you have installed that mod, try the following changes to
> the KSB2 board:
> 1 - Change R9 to 15k
> 2 - Cut the trace (on the top of the board) between P1 pin 6 and the base
> of Q1 and insert a 1k resistor between those two points. You will have to
> orient the resistor vertically, or use an SMD resistor.
>
> That should calm the ALC overshoot when operating into a dummy load.
>
> The question still remains about the original problem which was an
> overshoot problem on 40 meters. If that persists when operating into an
> antenna, the KPA100UPKT is the solution.
>
> 73,
> Don W3FPR
>
>
> On 8/31/2010 6:54 AM, Ken Cannaday wrote:
>> Thanks much for the comments, all were very helpful and are much
>> appreciated. I did some further testing along the lines suggested with
>> the
>> following results:
>>
>> Settings: SSBA = 1; SSBC = 3 to 1; requested power QRP = 2, QRO = 20;
>> transmitting into a dummy load; microphone = Heil HC4 (but similar
>> results
>> have generally been experienced with Icom electret hand mike, HM 36); all
>> bands tested in both TUNE and SSB modes .
>>
>> Generally in QRP on TUNE mode, I saw anywhere from 2.8 to 2.3 watts after
>> the ALC had time to settle in (the ALC seems to start over with any
>> change
>> in band or certain other settings). In particular, I saw 2.8 watts on
>> 160,
>> 2.3 on 10 meters, with the other bands somewhere in between. In SSB, I
>> generally saw peaks at one or two bars, with an occasional third bar, for
>> ALC; and two bars with an occasional third bar for RF. The exceptions
>> were:
>> 80 meters, where there was a very brief initial surge up to 4 or 5 bars
>> before settling in at 1 to 3 bars for ALC, and 2 to 3 bars for RF; 40
>> meters, where again there was the initial surge in reading before
>> settling
>> at 3 to 4 bars for both ALC and RF; 30 meters where the results were
>> similar
>> to 40 meters except that RF eventually settled to only 2 to 3 bars.
>>
>> Then switching to QRO, on Tune mode, I saw 19, 20, or 21 watts on all
>> bands
>> except on 80 meters where the ALC never seemed to settle in and kept
>> bouncing around between 18 and 22 watts, with 19 being the most stabile
>> eventual reading. In SSB, I generally saw peaks at 1 (10 and 12 meters),
>> 1
>> to 2, or 2 to 3 (160) bars for ALC and 2 to 3 bars for RF. On 80 meters,
>> however, there was again an initial surge, lasting a little longer and
>> settling in a little slower to an eventual 2 to 3 bars for ALC and a
>> solid 3
>> bars of RF; on 40 the initial surge was more extreme with the ALC kicking
>> up
>> as high as 6 bars before settling in at 3 to 4 bars, 2 to 3 bars for RF.
>> The most extreme results were on 30 meters where I saw readings as high
>> as 5
>> to 6 bars for ALC and 7 to 10 bars for RF. After a much longer period of
>> speaking into the microphone, eventually readings settled respectively to
>> 3
>> to 4 bars with a rare 5th bar and 2 to 3 bars with an occasional 4th bar.
>>
>> I should add that I can generally get a bit higher readings by screaming
>> into the microphone, but the results summarized above were obtained by
>> speaking just a bit louder than normal, as if I am excited on the verge
>> of
>> working a new, rare DX entity.
>>
>> Generally a higher RF reading was supported by a higher ALC reading.
>> Does
>> this indicate that any excess in power output is not likely to be an ALC
>> problem rather than a KPA/100 problem? How necessary do you think it is
>> to
>> install the KPA100UPKT given these results? Any observations or
>> suggestions
>> would be appreciated.
>>
>> 73
>>
>> Ken
>>