Unstable KPA3-100W

[K5RC]

I got a number of reports from SS CW of spurious signals. I have isolated it
to one K3 (S/N 4498). With the KPA3-100 disabled (below 12 watts) the signal
is clean. From about 13 watts to 90 watts, there are spurious signals about
every 1KHz  + and - the carrier frequency. The frequency of the spurs
changes as the power control is advanced and the signal becomes clean again
at about 90W. This happens on 80, 20 and 10 (the only bands this radio has
antennas for). Also, the power output is unstable on the wattmeter and the
SWR apparently changes continually indicating a wandering spur.

 

Any ideas?

 

Tom Taormina, K5RC

The Comstock Memorial Station, W7RN

Virginia City NV

http://k5rc.cc 

 

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[K2QI]

Hi Tom,

Have a look at the following technical bulleting from Elecraft:

http://www.elecraft.com/K3/mods/K3%20Technical%20Alert%201.pdf

Does your KPA3 have capacitor C3 installed? If so, that may be your problem.

73 de James K2QI

On Mon, Nov 15, 2010 at 9:50 PM, K5RC <[hidden email]> wrote:

> I got a number of reports from SS CW of spurious signals. I have isolated
> it
> to one K3 (S/N 4498). With the KPA3-100 disabled (below 12 watts) the
> signal
> is clean. From about 13 watts to 90 watts, there are spurious signals about
> every 1KHz  + and - the carrier frequency. The frequency of the spurs
> changes as the power control is advanced and the signal becomes clean again
> at about 90W. This happens on 80, 20 and 10 (the only bands this radio has
> antennas for). Also, the power output is unstable on the wattmeter and the
> SWR apparently changes continually indicating a wandering spur.
>
>
>
> Any ideas?
>
>
>
> Tom Taormina, K5RC
>
> The Comstock Memorial Station, W7RN
>
> Virginia City NV
>
> http://k5rc.cc
>
>
>
> ______________________________________________________________
> 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
>

--
73 de James K2QI
President UNARC/4U1UN
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