[CQ-Contest] ANOTHER CAUSE OF UNINTENDED DUPES

[T A RUSSELL]

DUPES as a result of OFF  FREQUENCY  CALLING  -  de  N4KG

One contributing factor to dupes that I have not seen addressed
is  OFF   FREQUENCY   CALLING.  This is not as big a problem
as it was 10 years ago, but it still happens.  If the caller is a little
high in frequency and there is another station calling CQ above
the desired target station, the higher station may log the caller,
UNKNOWN to the caller.  When he later comes across the 
unintended station, he is told he is a DUPE, but the new target
station  does not  appear in the caller's log.

For unknown reasons, most manufacturers set their radios up
with an 800 Hz offset for CW.  This meant that for the transmit
signal to be zero beat with the received station, the operator
had to listen to an 800 Hz pitch.  

I find that most people prefer a much lower pitch (400-500 Hz)
which places their 800 Hz offset 300 to 400 Hz above the 
received signal.  (For low band DXing, I prefer even an even 
lower pitch in the 200 to 300 Hz range.  To me, it is easier to 
extract weak signals from the noise with a very low pitch).   
Fortunately, the newer (especially top of the line) radios 
track the transmit offset with receive pitch.

To determine your radio's offset, place the radio in TRANSMIT
while in the CW mode.  Set the VFO to read  XX00.0.  Switch 
back to receive mode.   Turn on the calibrate signal 
(if you have one, otherwise,  use  WWV).  If the received pitch
is NOT at your desired listening pitch, adjust the RIT or PITCH
control to bring the received signal to your preferred pitch.  
Now your transmit frequency will be zero beat with the
received signal.  DO  NOT  tune the VFO during this adjustment.

For older KENWOOD  radios (TS-530, TS-830, others?) the 
CW  Transmit Offset is determined by a small coil switched
in circuit during transmit.  This (1 uH ?) coil can be replaced
with a 2.2 uH coil to change the 800 Hz offset to around 400Hz.

de  Tom  N4KG  (receiver design engineer in my other life)



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