[NLRS] Left Field (or maybe even outside the ball park) thought on VHF Field Day modes

[Doug Reed]

Yes, I made a comment about there being no reason that you couldn't
run MCW or other audio-based digital modes over a FM voice radio. What
is important is that all the contact info is sent in that mode if you
are counting it as a CW or digital contact, not as a voice contact.
Although I'm not sure how good the results will be when you are waving
the mike in front of the computer speakers to send the data... :-)

What you describe has been seen frequently in the local FLDIGI
training sessions put on by the ARES folk. It works, but obviously it
is more of a last resort and not something you should count on. And I
wouldn't expect it to work for beans with a weak SSB signal....

If you decide to try that, just be sure you click on the FLDIGI
waterfall at 1000Hz before you try to send. That will tell FLDIGI what
audio tones it needs to generate or listen for. If you click on 1000Hz
and your partner is using 800Hz because he likes the CW tone better,
nothing will be decoded....

It is also a bit of an advantage to be using tones around 1000Hz since
that is usually the middle of the audio passband and is capable of max
power from the radio. If you clicked on the waterfall above 2500Hz or
below 400Hz, there is likely to be significant drop-off in RX and TX
signal levels which would make things more difficult than they need to
be....

If in doubt, you might want to test your sound card interface to see
if the frequency response is flat from 300Hz to 3000Hz. I mention this
because I had trouble with an audio interface this spring where the
miniature transformer was operated into high-impedance and the
frequency response fell about 20dB from 2KHz to 300Hz.... I solved
that by using low-impedances for everything around the transformer and
the signal source. For testing your interface you can use an audio
generator and scope if you have one, else I recommend the TMS-1 audio
test software from the DazyWeb Lab freeware page.
<http://infinitespectra.com/freeware/>

73, Doug Reed, N0NAS.