The question about sending data using subaudible tones reminded me of a
quick 'n dirty soundcard digital setup I found for use over voice repeaters.
You can't talk while its working, but it does allow you to go back 'n forth
between voice and data. There are probably times when that would be useful.
I was playing around with FlexNet's Flex32 version of Q15x25 mode, called
"newqpsk". This mode is intended for HF, and uses fifteen 88.3 baud PSK
streams to give you an effective 2500 baud. I decided to try it out on VHF,
then decided to try bumping the TXDELAY up around 500-600 MS and see if it
would work over the local voice repeater, connecting to another VHF newqpsk
station in town on that frequency.
It worked very well! I was at home, and my friend had a laptop in his truck
across town. We were able to do all the regular digital stuff. Newqpsk is a
lot like packet to use, but of course sounds very different. You can send
binary files with it, because it has error correction like packet.
The easiest way to check out newqpsk in Flex32 is to see the "Soundcard
Packet" tutorial at USPN, that describes the setup of Flex32 for 1200 baud
afsk packet. On the part where you choose afsk for the soundmodem from a
dropdown menu, just go down to the bottom of the list and choose newqpsk
instead. That's the main difference between setting Flex32 up for newqpsk
instead of packet. When reading the tutorial, don't miss the part at the
last where it recommends the PAXON terminal program. You'll be glad you did,
PAXON is really nice.
This is not bad; A 2500 baud digital setup that can be used anywhere there
is a voice repeater. The high TXDELAY introduces some slowup, but overall
it's fairly snappy. - Good enough to get some lengthy or involved text sent
across, or perhaps a small binary file like a JPEG. Since it's a soundcard
mode, it's very portable and the price is right too. (free)
Note: The MixW Q15x25 dll package sets you up with an interleave of 16. To
make the Flex32 newqpsk version compatible on the air with MixW stations,
bump its interleave up to 16 as well.
Charles Brabham, N5PVL
http://www.uspacket.net