Re: K2 signal tracing progress and questions arising
Posted by
Don Wilhelm-4 on
Nov 22, 2009; 2:11pm
URL: http://elecraft.85.s1.nabble.com/K2-signal-tracing-progress-and-questions-arising-tp3982841p4046290.html
Paul,
Rather than trying to do your proposed test, I would suggest you look
carefully at the T/R switch area first. Typical problems are diodes
oriented wrong (check against the Parts Placement diagram in the back of
the manual). A broken lead (or unsoldered, poorly tinned, etc.) of RFC3
could cause similar problems - be certain RFC3 is wound on a ferrite
core (dark gray) and not one of the black cores.
73,
Don W3FPR
Paul Fletcher wrote:
>
> Don Wilhelm-4 wrote:
>
>> A drop in signal at the receive output of the LPF could also be caused
>> by a T/R switch problem.
>>
>>
>
> Update so far. Having terminated the LPF's in a 50 ohm resistor I can
> definitely confirm all of the LPF's are fine. I measured swr and monitored
> in / out on the scope and loss is negligible. As soon as I reinstate W1 the
> output of the LPF is pulled low (50% of level when terminated with 50 ohms).
> I guess the next step is to do the same check with the chain broken after
> the T/R switch and progressively work down the chain. The is no ground short
> on the input to the band pass filters at DC. I can't directly terminate the
> T/R switch at W6 because of the DC bias so what value blocking cap should I
> use?
>
> Any other thoughts appreciated.
>
> 73 Paul M1PAF
>
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