[OZAPRS] PSK63 for APRS on HF

Wed Apr 9 13:47:55 EST 2014

According to the author of APRS Messenger, MFSK16 can work down to a 
signal to noise level of -13.5 dB in a 3 kHz bandwidth. That's 2 dB 
better than PSK-31 or 6 dB better than PSK-63. It also has forward error 
correction and an interleaver so that noise spikes and lightning crashes 
don't lose data.

MFSK16 can be transmitted at full power like the GMSK modes so that adds 
an extra 3 dB to the link budget as the transmitter doesn't have to be 
run at half power as with PSK modes. There are multiple software 
receivers on MFSK16 giving a maximum tuning range of ± 75 Hz.

Switching to MFSK16 here the beacons became almost twice as long as for 
PSK63. The reward was immediate as the WA8LMF 
<http://aprs.fi/info/WA8LMF-13> iGate in Michigan started receiving 
these transmissions on 30m. I'm using 50W into a low dipole and WA8LMF 
uses a magnetic loop. 5W would certainly give Australia-wide coverage. 
Transmission length can be reduced by using the compressed APRS format 
though can never be as short as for FSK300. Where the power budget is 
low like on a balloon, MFSK16 would be ideal.

Cheers,
Gerard - VK2IO

On 8/04/2014 12:49 PM, Mark Jessop wrote:
> Going from experience, and a lot of simulation and on-air testing, I'd 
> say MFSK16 will be a far more reliable system than PSK63, mainly due 
> to it's r=1/2 forward error correction. You probably wouldn't need 
> much more than 5W for australia-wide coverage.
>
> It's also fairly easy to generate (with a DDS anyway), and is constant 
> amplitude (no linear amp required!), so you could make a 5W MFSK 
> beacon using a Class E PA running at >95% efficiency.
>
> The main downside is it is slow, so channel congestion becomes more of 
> an issue.
>
> Cheers,
> Mark
>
>
> On 8/04/14 11:54 AM, Gerard Hill wrote:
>> About 4 years ago a bunch of us started experimenting with PSK 
>> <http://wa8lmf.net/APRS_PSK63> for APRS on HF. We used the APRS 
>> Messenger <http://www.crosscountrywireless.net/aprs_messenger.htm> 
>> software which supported a variety of speeds from 31 to 250 bps. It 
>> proved far superior to FSK300 packet. I ended up running an IGate on 
>> 7034.7 kHz and a receive-only IGate on 10149.7 kHz. These PSK ports 
>> closed 2 years ago.
>>
>> APRS Messenger requires a PC running Windows and continues to be 
>> developed so now supports GMSK250 
>> <http://www.radio-electronics.com/info/rf-technology-design/pm-phase-modulation/what-is-gmsk-gaussian-minimum-shift-keying-tutorial.php> 
>> and MFSK16 modes as well as PSK63 and PSK250. APRS messages contain a 
>> checksum allowing posits to be verified before injection into the 
>> APRS-IS. It is great software for the shack, not so convenient in the 
>> mobile where a compact tracker is needed.
>>
>> Last year, the FreeTrak63 
>> <http://www.ringolake.com/pic_proj/FT63/ft63_page.html> was developed 
>> for mobile use. It can generate PSK63 and MFSK16. Blank PCBs are 
>> available.
>>
>> Anyone interested in trying PSK63 for APRS?
>> I'm running it on 10149.7 at the moment using VK2IO-63.
>>
>> Cheers,
>> Gerard - VK2IO
>>
>> On 4/04/2014 8:00 AM, Andrew Rich wrote:
>>> Psk had very good noise performance
>>>
>>> Psk63 is faster than psk31
>>>
>>> No error check tho
>>>
>>> Sent from my iPhone
>>>
>>>> On 4 Apr 2014, at 6:58 am, Matt VK2RQ<matt.vk2rq at gmail.com>  wrote:
>>>>
>>>> This is an interesting article on that topic:
>>>> http://wa8lmf.net/APRS_PSK63/
>>>>
>>>> 73,
>>>> Matt VK2RQ
>>>>
>>>>> On 4 Apr 2014, at 7:37 am, Shaun<vk2xpp at optusnet.com.au>  wrote:
>>>>>
>>>>> What is the advantage of psk63?
>>>>>
>>>>> Brief reply only from my iPhone
>>>>>
>>>>>> On 3 Apr 2014, at 17:56, Andrew Rich<vk4tec at tech-software.net>  wrote:
>>>>>>
>>>>>> Just got a icom 7000 and scs packet modem will see if it does psk63
>>>>>>
>>>>>> Sent from my iPhone
>>>>>>
>>>>>>> On 3 Apr 2014, at 2:49 pm, Andy Nguyen<an at comms.net.au>  wrote:
>>>>>>>
>>>>>>> Thanks Mark,
>>>>>>> Just checking :)
>>>>>>> Regards
>>>>>>> Andy VK3YT
>>>>>>>
>>>>>>>> On 3 Apr 2014, at 3:35 pm, Mark Jessop<lenniethelemming at gmail.com>  wrote:
>>>>>>>>
>>>>>>>> Planning on a HF balloon payload there Andy?
>>>>>>>>
>>>>>>>> And AFAIK there's no PSK capable iGates in Australia.
>>>>>>>>
>>>>>>>> - Mark VK5QI
>>>>>>>>
>>>>>>>>> On 3/04/14 3:04 PM, Andy Nguyen wrote:
>>>>>>>>> Hi all,
>>>>>>>>> Do we have any iGate on HF (30m) in Australia that supports PSK63 ?
>>>>>>>>> Regards
>>>>>>>>> Andy
>>>>>>>>>
>>
>>
>>
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