Posted by
Don Wilhelm-4 on
Aug 31, 2010; 1:11pm
URL: http://elecraft.85.s1.nabble.com/K2-KPA-100-excessive-power-issue-SSB-mode-some-bands-tp5470018p5482562.html
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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