[AMRadio] re: Apache audio not good

[W7QHO at aol.com]

All,

I would second Ed's recommendations, i.e., up the input impedance, increase 
the coupling capacitance in the speech amp stages and pull the 6AL5 clipper.  
I would also recommend  removing the LP filter.  I don't know if this was 
true of all Apaches but in mine the filter characteristic had a deep notch 
around 1500 cycles and then didn't drop off again until about 8 kHz.

In preliminary tests I also found the clipper circuit to be poorly designed 
in that the clipping levels varied according to the speech duty cycle.  I was 
able to cure this with a couple of zener diodes but finally decided to 
eliminate the whole clipper/filter circuit when I discovered the LP problem 
described above.  I've been getting great audio reports ever since (almost 20 
yrs).

The original driver transformer is OK, BTW.  Dinky little thing but as I 
remember the response was good out to 10 kHz or so.

Dennis D.  W7QHO
Glendale, CA