Re: K2 signal tracing progress and questions arising
Posted by
Don Wilhelm-4 on
Nov 11, 2009; 10:47pm
URL: http://elecraft.85.s1.nabble.com/K2-signal-tracing-progress-and-questions-arising-tp3982841p3989552.html
Paul,
With an ohmmeter, everything will look shorted in the LPF section. If
you have an antenna analyzer, you can remove the W1 jumper and terminate
the LPF side with a 50 ohm resistor - connect the antenna analyzer to
the antenna jack and scan through the filter passband - you want to do
that for each band. If you see a large SWR, then check the LPF
corresponding to that band.
A drop in signal at the receive output of the LPF could also be caused
by a T/R switch problem.
73,
Don W3FPR
Paul Fletcher wrote:
>
> Don Wilhelm-4 wrote:
>
>> Paul,
>>
>> My only thought on the bandpass filter "weirdness" is that either the
>> bandpass filter is not properly terminated at the D6/D7 junction, or
>> that your 'scope probe is picking up something extraneous - change the
>> routing of the ground on the 'scope probe and see if there is any change.
>>
>>
>
> OK fixed the voltage discrepancy by limiting the bandwidth on the scope
> (measurement issue). One problem appears to be in the chain up to the
> receive mixer. I'm losing about half of the signal but I'm not sure if it's
> the low pass filters or something after the LP filters pulling the signal
> down. Next steps are to check for ground shorts in the LPF bank. Another
> check I thought of doing is terminating the LPF (by opening W1) into a 50
> ohm resistor and checking that out. If that's OK open W6 and do the same
> check (to check the T/R switch).
>
> Any other suggestions?
>
> Cheers,
> Paul.
>
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