[Boatanchors] Questions on 51J4 as Ham receiver

WA5CAB at cs.com WA5CAB at cs.com
Mon Nov 6 12:39:17 EST 2006


Eugene,

Step Zero is to make sure that when you put the BFO tuning knob on 0 the BFO 
is actually tuned to the middle of the IF passband.  This is normally one of 
the last steps in the IF alignment procedure.  Having done that, the BFO front 
panel markings read directly in KC/s.  How far to offset the BFO for tuning 
CW, FSK or SSB depends on the IF bandwidth or in your case which mechanical 
filter you are using.  Generally you would offset the BFO by one-half the filter 
bandwidth or so, placing the BFO right on or just outside of one of the filter 
skirts.  Which direction to offset it depends, as Glen indicated, on the 
conversion scheme used in the receiver, which may not be the same on all bands.  
Having done this when you tune in a signal it should be more or less centered in 
the receiver passband.

You can, of course, make the receiver work and receive SSB signals without 
the BFO zero set to the center of the passband but if you switch from USB to 
LSB, the number the knob points to won't be the same on both sides.  It makes it 
easier to remember what to set the knob to if zero is zero.

In a message dated 11/6/2006 11:12:06 AM Central Standard Time, 
gzook at yahoo.com writes: 
> For SSB the BFO frequency is placed on one side of the
> i.f. filter or the other.  Which side depends on which
> sideband you are receiving.  Set the BFO to around 1.5
> KHz to either side and then tune the main tuning dial
> to hear the signal.  If you cannot tune that
> particular sideband very well then tune the BFO to the
> other side and you will then be able to receive the
> SSB without any problems.  Make a note as to which
> side you have to tune for USB and which side for LSB
> for each band.
> 
> This is the same for all of the older receivers that
> have variable BFOs.
> 

Robert Downs - Houston
<http://www.wa5cab.com> (Web Store)
MVPA 9480
<wa5cab at cs.com> (Primary email)
<wa5cab at houston.rr.com> (Backup email)


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