[R-390] A Few Questions

[DJED1 at aol.com]

Sounds pretty normal to me.  If you center the BFO in the passband,  you will 
hear both sides of the signal as you tune off.  If you choose 2 Kc  
bandwidth, for example, and offset the BFO by 1.2 Kc, you should eliminate most  of one 
sideband, while the other sideband should be good until you've tuned off  by 
about 2 kc.  To check the BFO alignment, set the BFO to center on the  
narrowest passband (0.1 Kc) by peaking up the signal at that filter setting,  then 
loosen the BFO knob and set for 0 when it is zero beat with the  signal.
 
The audio filter is intended for very tight CW work, and if I remember  right 
is tuned to about 700 cycles.  So you must peak up the signal in the  IF 
filter, then set the BFO to give you a 700 cycle beatnote, then turn on the  audio 
filter.  It's very effective for weak CW signals.
 
I'm not much of a CW man, but I used the audio filter to make a frequency  
measurement a while back:  I bought a HP synthesized generator that reads  out 
to 1 Hz, and I wanted to see how accurate it was by comparing it to  WWV.  I 
coupled the generator to the antenna so I could hear the beat note  between WWV 
and the generator. Well, between the modulation and noise on  WWV I couldn't 
tell the zero beat to much better than 10s of Hz, so I  offset the generator to 
10.000700, turned on the audio filter, and hooked up a  frequency counter to 
the audio output.  The filter cleaned up all the  noise, and the counter could 
read the 700 Hz signal to about +-1 Hz, and that  was close enough for me. 
Generator was dead on.
The generator makes it a snap to check the linearity of the PTO without  
taking things apart to hook up a counter to the PTO.
Ed
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