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Old October 29th 05, 01:43 PM
William E. Sabin
 
Posts: n/a
Default BFO, CW, sideband question

Modern radios such as the FT1000MP Mk V automatically change the internal
local oscillator frequencies so that USB, LSB and CW appear on the same
indicated signal frequency, which is what we want. In CW we get a certain
pitch frequency such as 500 Hz (not zero beat) at the signal frequency. The
value of this pitch frequency can be changed from the front panel by the
operator to suit his preference.

In my homebrew rcvr I use the CW USB setting only. As I tune up the band I
hear the high pitch of a signal first and it then decreases pitch as I
continue to tune up the band (my preference). I use a single xtal filter
frequency for USB/LSB and a single xtal filter frequency for CW. The BFO
xtal frequency and the VFO frequency counter digital readout (not the actual
VFO frequency itself) are automatically changed to their correct values in
LSB, CW or USB mode. In CW mode I then have a 500 Hz beat note, which is
what I want, not zero beat, and the CW BFO xtal is then the correct value
for CW USB.

For a brief description of my homebrew rcvr see QRZ.COM, W0IYH.

Bill W0IYH

"Wor" wrote in message
...
Hi!
Just to make things more complex (or simple). When you tune from LSB to
USB
you also change the frequency of BFO, putting it on one side or another of
the IF filter. If you listen to LSB on USB position you can put the
simulated carrier frequency on the right place, but signal is out of IF
passband.
Sorry for my bad English. Hope you understand.
Damir 9A3IV