[Elecraft] K2 Build # 653 SSB issues.

[Don Wilhelm]

  Nidge,

First help me establish the level of your KPA100.
Do you have blue toroids at RFC1 and L16?  If so, look at the value of 
C31 - it should be 0.22 uF.  If C31 is 0.033 uF (33nF) it must be changed.

If you have red toroids at L15 and L16, then your first step is to 
install KPA100UPKT.

There are other possibilities with the shield.  The gap at the SO-230 
jack should be less than 3mm, you should have solder lugs connecting the 
SO-239 jack directly to the shield, and the shield should have 3 clips 2 
of which should contact unpainted metal on the base K2 side panels.  If 
that is not the case, then you must update the shield kit.  Yes, the 
KPA100 can oscillate if it is not properly shielded from the circuits in 
the base K2.

73,
Don W3FPR

On 6/17/2011 7:20 AM, Nigel (Nidge) Smith wrote:
> Hi All
>
> I have in my possession a K2 with the following options.
>
> KPA100, KSB2, K160RX, KNB2, KDSP2, .
>
> I’m not the original builder of this example and the source of the original builder is a little vague.
>
> So far I have done a complete reset of the radio, fine tuned the alignment of the bandpass filters
> in the base, aligned the CW and SSB filters. As of yet I haven’t looked inside the KPA100 option, which
> is mounted internally.
>
> There are a few issues with this radio but the one I’m concentrating on at the moment is to do
> with the SSB performance in conjunction with the KPA100. These can be seen below:
>
> 160m – Using the tune button produces 100Watts, SSB the radio folds back to about 5 Watts.
>
> 80m – All seems fine.
>
> 40m – When the power control is advanced to engage the KPA100 and the tx is peaked with a whistle the radio goes
> into self oscillation, no issues on CW.
>
> 30m – Display reads high current and the TX folds back to about 5 Watts.  No issues noted when the KPA100 is
> disengaged.
>
> 20m -  All appears to be fine.
>
> 17m – Display reads high current and the TX folds back to about 5 Watts. No issues noted when the KPA100 is
> disengaged.
>
> 15m – All appears to be OK
>
> 12m – All appears to be OK, max TX power is about 70Watts
>
> 10m – All appears to be OK, max TX power is about 65-70Watts.
>
> There is an intermittent issue when stepping through the bands up to 15m/12m/10m  when there is no TX output
> or receive. Switching the radio off and back on seems to cure this.
>
> Any advice gratefully received.
>
> Nidge (G0NIG)
>
> IO93dv
>
>
>
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