Re: Data over VHF/UHF FM

[John P. <kl...@gm...>]

Hi John Brooks,

Glad to see the interest in VHF and UHF FM data :)
In the 3.22 releases of Fldigi, there are the modes 8psk 1000 and 8psk 1333
which transfer at 3kbps and 4kbps respectively. Neither uses forward error
correction, nor is it normally needed. Both of these modes are designed for
FM usage specifically.

The 1666 baud mode was abandoned as it seemed to work with some radios and
repeaters, but not others.
My future development path has headed towards using the "9600 port" on FM
radios, thereby giving about 7khz of available audio bandwidth.
This extra bandwidth would support about 10kbps of data (theoretical max)

My development laptop was unfortunately stolen from the laundromat, so I am
re-working from recent backups.

Will try to get some code posted soon and keep you informed
73's
John Phelps
KL4YFD

========

On Monday, February 16, 2015, John Brooks <jo...@fa...> wrote:

>  I've been wanting to do some experiments with digital data sent through
> an FM voice channel on the 2m/70cm amateur bands. A lot of (indeed, most
> of) the digital modulation schemes that use audio are meant for use on HF
> bands, where bandwidth is very limited. They don't adapt well to use on
> wide-band FM voice channels; much of that lovely 3kHz of audio bandwidth
> goes to waste on a narrow signal.
>
> Anyway... getting to the point, I noticed that you've been developing a
> 1600 baud 8PSK modulation scheme for implementation in fldigi. This sounds
> very promising in filling the niche I mentioned above; the need for a
> digital modulation scheme that takes full advantage of a wide-band amateur
> FM voice channel.
>
> I just wanted to express my interest in this and ask if it's still being
> worked on. I also would like to know if it's planned to make FEC togglable
> again to allow higher bitrates on PSK modes.
>
> 73 de VE3HCF :)
>
> --
> *John Brooks* | Webmaster http://www.fastquake.com/
>