Murray Parnell vk2umz at gmail.com
Sat Dec 2 11:40:38 AEDT 2017

Hi Glen
Read this

Murray (VK2UMZ)

On 2 Dec 2017 9:54 AM, "Glen English VK1XX" <glenlist at pacificmedia.com.au>

> Hi Mark
> Yeah no need to preserve AX25 frame precisely agreed, just need to be
> interface compatible.  I've got a few HF modems up my sleeve, most require
> *some* linearity in the PA, so maybe just move to nFSK /single tone this
> tends to be more tolerant to bad setup...especially when the aim is to
> share the nearby spectrum. With the single tone modes, if they are kept
> >1400Hz in the microphone input, the overdriving distortions usually don't
> get through the SSB filter...
> And Andrew, most microcontrollers can execute reasonable modems these
> days, there is enough grunt, there is a blur between general purpose
> microcontrollers and dedicated DSPs. Where help is required is on the
> decode side for the FEC, especially with large frame sizes (which yields
> greater "coding gain") , For a signal sense mode, it only has to detect the
> presence of a signal, not fully decode it. For decoders, things like
> Odroids and other small linux boxes make excellent demods.
> On 2/12/2017 10:51 AM, Mark Jessop wrote:
>> FT8, JT65 and similar are far too restrictive for something like HF APRS.
>> They are quite specifically designed for making short QSOs, not for passing
>> of arbitrary data (though is is possible, in a limited sense). Take a look
>> at the JT65 spec and you will see what I mean.
>> The concept of a MFSK-based mode with *good* FEC is still a good one
>> though, but you'd probably be better off either rolling your own or
>> starting from something like THOR or Olivia.
>> Would the AX25 packet format still need to stay? If you could drop that
>> it would give a lot more flexibility...
>> 73
>> Mark VK5QI/VK4
>> (Currently SW of Longreach...)
>> On 2 Dec. 2017 08:15, "Glen English VK1XX" <glenlist at pacificmedia.com.au
>> <mailto:glenlist at pacificmedia.com.au>> wrote:
>>     I have my own low bit rate HF capable position/ aprs reporting
>>     modem etc but I was thinking at FT8, given the widespread use,
>>     would make a good replacement for FSK300 (which is dumb arse
>>     poorly suited with no FEC on HF), and that the decoders allow for
>>     multiple simultaneous overlapping transmissions in the same BW.
>>     doing a port for dire wolf would be fairly straightforward.
>>     glen Vk1XX
>>     _______________________________________________
>>     OZAPRS mailing list
>>     OZAPRS at aprs.net.au <mailto:OZAPRS at aprs.net.au>
>>     http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>     <http://lists.aprs.net.au/mailman/listinfo/ozaprs>
>> _______________________________________________
>> OZAPRS mailing list
>> OZAPRS at aprs.net.au
>> http://lists.aprs.net.au/mailman/listinfo/ozaprs
> _______________________________________________
> OZAPRS mailing list
> OZAPRS at aprs.net.au
> http://lists.aprs.net.au/mailman/listinfo/ozaprs
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.aprs.net.au/pipermail/ozaprs/attachments/20171202/5579a656/attachment-0001.html>

More information about the OZAPRS mailing list