[AMRadio] Re: GB> 75A-2 project


sbjohnston at aol.com sbjohnston at aol.com
Tue Jan 29 22:59:01 EST 2008


Follow-up to my earlier postings on my 75A-2 project...

I experimented with increasing the value of capacitance from the top of 
the IF transformer primaries to the top of the secondaries - to broaden 
the basic IF bandwidth - and had some success.  This is the opposite of 
the narrow-banding mod in the manual.

I ended up with the original 5 pF plus another 10 pF on T4 and T5, and 
the original 10 pF plus an additional 22 pF on T6.  I tried the same 
thing with T7 but that seemed to cause a considerable degradation in 
the ultimate rejection (strong signals elsewhere in the band bled 
thru).  Decreasing the Q-spoiling resistance on T3 didn't make much 
difference except to reduce the gain.

Steve WD8DAS

sbjohnston at aol.com
http://www.wd8das.net/
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