[Elecraft] K2 signal tracing progress and questions arising

[Don Wilhelm]

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. 
>