Posted by
Ken Cannaday on
Aug 31, 2010; 6:23pm
URL: http://elecraft.85.s1.nabble.com/K2-KPA-100-excessive-power-issue-SSB-mode-some-bands-tp5470018p5483897.html
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
>>
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