[OZAPRS] FT8 for HF APRS ?
Glen English VK1XX
glenlist at pacificmedia.com.au
Sat Dec 2 14:13:10 AEDT 2017
There are a few adaptable protocols ,
requirements
symbol rate < 60 baud
some FEC to tolerate at least one static crash/ suboptimal clock recovery
bandwidth occupied narrow,
insensitive to frequency accuracy,
tolerant of short term frequency drift,
multipath tolerant to 6mS at 0dB and 7.2Hz doppler spread
single tone transmission for non linear amplifier,
tolerant of high AM to PM amplifier conversion,
performance at 0dB CNR
On 2/12/2017 2:04 PM, vk4tec at tech-software.net wrote:
>
> So whats the solution fellas
>
> I have been playing APRS up at 915 MHz
>
> Time to try DC
>
> Andrew
>
> *From:*OZAPRS [mailto:ozaprs-bounces at aprs.net.au] *On Behalf Of
> *Murray Parnell
> *Sent:* Saturday, 2 December 2017 12:04 PM
> *To:* Australian APRS Users <ozaprs at aprs.net.au>
> *Subject:* Re: [OZAPRS] FT8 for HF APRS ?
>
> Hi Warren
>
> There are no wspr igates that i am aware of.
>
> I am not a software guy but the wspr decoding software by Joe Taylor
> is open source.
>
> The wspr encoder from qrp labs would be ideal for aprs as it already
> has a GPS interface for location, timing and frequency reference. It
> would just need someone to change the firmware to encode in aprs format.
>
> https://www.qrp-labs.com/ultimate3.html
>
> I would be happy to host a wspr aprs igate if the software was available.
>
> How about it Glen ?
>
> Murray
>
> (VK2UMZ)
>
> On 2 Dec 2017 10:48 AM, "Warren_Brown" <warbn at telstra.com
> <mailto:warbn at telstra.com>> wrote:
>
> Interesting idea, but is there any APRS WSPR gates running?
>
> Warren vk3byd
>
> *From:*OZAPRS [mailto:ozaprs-bounces at aprs.net.au
> <mailto:ozaprs-bounces at aprs.net.au>] *On Behalf Of *Murray Parnell
> *Sent:* Saturday, 2 December 2017 11:41
> *To:* Australian APRS Users
> *Subject:* Re: [OZAPRS] FT8 for HF APRS ?
>
> Hi Glen
>
> Read this
>
> http://aprs.org/aprs-wspr.html
>
> Murray (VK2UMZ)
>
> On 2 Dec 2017 9:54 AM, "Glen English VK1XX"
> <glenlist at pacificmedia.com.au
> <mailto:glenlist at pacificmedia.com.au>> wrote:
>
> 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>
> <mailto: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
>
>
>
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