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Old October 29th 05, 04:49 AM
Jaggy Taggy
 
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Default BFO, CW, sideband question

I started this thread because there is a bit of confusion in my head
regarding where the signal is, where the carrier is and what is indicated on
my radio dial.

And by the way, I do have an older radio, a Kenwood TS 830, not a modern
radio. My radio-display shifts on transmit to a frequency 800 Hz higher than
what was displayed on receive.

So I assume it displays the carrier frequency on transmit, while on receive
it displays the heterodyned frequency, which on my radio happens to be
lower, but as some indicated in this group, this is an arbitrary choice made
by the people at Kenwood.


The ARRL CW transmissions frequencies, for example, seem to be given for the
carrier which is not what my radio displays (my radio displays 800HZ lower
on receive) and therefore I need to adjust my radio to a different frequency
than what is advertised.

This is confusing to me.


It is also confusing me that I can't receive SSB on the lower bands using
USB (and a slight retune), I need to use LSB.
I don't know why since I learned that the two sidebands contain the same
info.


And the more I think about it the more I realize that I don't really
understand this whole topic very well...

Uwe





On 10/28/05 9:45 AM, in article
, "Tim Shoppa"
wrote:

Who decides to which side of the carrier the BFO will
heterodyne a CW signal.


For many SSB+CW transceivers, the maker of the transceiver decided on a
default sideband at manufacture time. Usually USB for rigs that are
capable of both sidebands.

For the oldest SSB equipment you don't get a choice of sideband:
14MHz and above comes out on USB, 7MHz and below come out on LSB, due
to the 9MHz IF + 5MHz VFO scheme.

I mean there must be convention, otherwise
we would have to find out on an individual basis


It doesn't matter as long as you're consistent between your TX and RX,
AND you make sure you're inside your band.

With most (all?) modern synthesized transceivers the frequency on the
display is that of the CW transmission in CW mode, but on older SSB+CW
rigs there was an offset (between a few hundred Hz and a few kHz)
between the dial and the actual CW transmission frequency (which was in
the sideband - the dial was calibrated to the suppressed carrier
frequency in USB/LSB). The offset was usually mentioned in the manual
(or in fancier rigs with RIT/XIT could be dialed in).

Tim.