A question to QRP PSK31 users and potential users: I am
trying to design a way to transmit PSK31 with simple
CW-only QRP transceivers. Besides the technical challenge
of getting a good-enough signal quality that way, there is
also a human-interface issue. I wonder whether people
would choose to use such a system, given the limitation
In normal use (with SSB rigs) one can see multiple
incoming signals in the "waterfall", click on the desired
one, and then the software generates an outgoing signal at
the same audio frequency as the chosen incoming one. That
way they end up on the exact same radio frequency.
My idea involves modulating the transmitter based on the
envelope of the PSK31 signal output by the computer. The
audio frequency of that envelope is ignored. That means
that one would have to do without that nice feature of the
PC software. Instead, one would need to do something like
this: find the signal you want to respond to, then tune
the rig's radio frequency so as to place that signal on
the waterfall at the same audio frequency as the (CW)
rig's tx/rx offset.
For example, if the transceiver transmits 700 Hz above (or
below) the "carrier" frequency during reception, then the
incoming signal should be producing a 700 Hz beat relative
to the BFO. One can mark (via software or otherwise) that
audio frequency on the waterfall to help with that
tuning. With some radios one can also see the outgoing
carrier on the waterfall by hitting the (CW) key for a
moment. (Arranging a way to do that at low power, without
actually transmitting, is an easy mod in some rigs.) The
tuning can be made more exact if the waterfall can be
zoomed in to show a narrower range around that frequency
than the typical 3 KHz band. Some existing PSK31 software
programs allow that, some don't.
OTOH if you are the one initiating the QSO (e.g. by
calling CQ) and the other party (using a conventional SSB
rig) replies right on your frequency, then all is good,
you wouldn't have to do anything further to tune it.
This is not really different from the way we use the rigs
for CW, where you tune the incoming signal to the same (or
close to the same) audio pitch as the offset (and the
sidetone, in the many rigs that generate the sidetone via
beating with the BFO).
So, would you live with such limitations for the purpose
of being able to use simple CW rigs (e.g., the
SW40/SW30/SW20, the similar MFJ rigs, HW7/8/9, and so
forth) for PSK31?
- Moshe, N1OVN