[TenTec] UCW and LCW
ken.d.brown at hawaiiantel.net
Fri Oct 27 23:05:03 EDT 2006
> When you go to LCW or UCW, the receiver is offset by the frequency of the
> "spot" frequency. Some times I have to check into the Badger Weather Net on
> 3985 on CW even though it is SSB. When I change from LSB to LCW and open
> the filter, I have to tune down 700 Hz to 3984.3 to copy the SSB. I then
> turn on the XIT and set it to -700 so they can copy my note. Otherwise I
> will be on 3985 and not create a tone in their receiver. Try it sometime.
This feature of modern rigs further confuses the issue. In SSB service,
the dial (or digital) frequency readout indicates the frequency of a
carrier that would be zero beat. Signals either side of that will
produce beat notes of greater than zero frequency. (apparently however
the guvmint has decided to use the center of the "channel" passband
instead of the zero beat frequency to designate the frequency of an SSB
channel, ala 60 meters)
Most of us do not listen to CW signals with the receiver set to have
them at zero beat, preferring an audio note with a frequency greater
than zero. In order to set our transmitter frequency to the same
frequency as the other station we want to work, it must be some amount
(several hundred Hertz) away from the zero beat frequency. In fact if we
want the be exactly on the other guys frequency, our transmit frequency
must be offset the same amount and the same direction as the other guy
is from our receiver's zero beat. In a good transceiver the "sidetone"
generated by the rig when you key it, will be the same as the note you
need to tune the other guys signal to, in order to get your transmit
frequency right on his. It makes sense to have the frequency readout
indicate where our transmitted signal will be (so we stay inside the
band limits) rather than where a zero beat received signal is. Yet this
can cause some confusion.
With separate transmitter and receiver, you just turn the TX VFO (in the
spot mode) until you hear the same note as the signal you are listening
to, and your receiver provides a sidetone. The transmitter does not have
to generate an audio tone for you to hear your sending. In this system
you can transmit on the opposite sideband, getting the same audio note,
yet not being on the same frequency as the station you are calling.
It's all relative.
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