[OZAPRS] HF APRS

Andrew Rich vk4tec at tech-software.net
Mon Dec 18 15:02:55 AEDT 2017


Is there a requirements spec

Is there a method of validation 

Sent from my iPhone

> On 18 Dec 2017, at 1:17 pm, Glen English VK1XX <glenlist at pacificmedia.com.au> wrote:
> 
> Yep
> 
> It's ready to go. But I have to get work done this week, got to go to sort a few things out at a few sites. I need to get some python code written before going to site tomorrow.
> 
> Over the weekend I remembered how it all works (it's a modem I wrote 4 years ago) , and modified a few blocks to reduce the CPU usage for this narrow band application, and also I added a block to generate IQ baseband signals from real input (radio output) , so it can use a standard radio.
> 
> Compilation targets are x86 and ARM+NEON... If compiling for ARM, it is HEAVILY NEON optimized as it had to run on a certain platform ... (oDroid) .
> 
> It searches through a specified bandwidth, throwing as many cores at it  as you tell it to, each core gets a chunk of spectrum to work on.  Roughly 50mS per second processing time per 2kHz of searching BW  on a 3.5 GHz i4670k single thread. Will run on a Odroid C1, C2, XU4 etc. might run on later Pis, never used them...
> 
> Sync can be acheived at about 9dB below what is required for a decode (~ 1dB SNR), the modem can decode multiple transissions simultaneously in the passband and used a 1/5 rate LDPC code. Modulation is D2BPSK (2nd order diff ).
> 
> g
> 
>> On 18/12/2017 1:30 PM, Graeme wrote:
>> Glen English has stated that he is working on something new for HF APRS that should be a lot better than what’s currently available.
>> Graeme 2HFG
>> *From:* Gerard Hill
>> *Sent:* Monday, December 18, 2017 11:25 AM
>> *To:* Australian APRS Users
>> *Subject:* Re: [OZAPRS] HF APRS
>> PAs - as in Power Amplifiers, Andrew.
>> In the past I've run an IGate using PSK63 and GFSK63 using software called APRS Messenger <http://www.crosscountrywireless.net/aprs_messenger.htm>.
>> These modes have great performance even without Forward Error Correction.
>> Availability for mobiles is limited although there is a standalone modem for PSK63 available called FreeTrak63 <http://www.ringolake.com/pic_proj/FT63/ft63_page.html>.
>> Some info on these modes from WA8LMF here <http://wa8lmf.net/APRS_PSK63/index.htm>.
>> Be interesting to know more about what Matthew is referring to.
>> Cheers,
>> Gerard - VK2IO
>> On 18 December 2017 at 11:01, <vk4tec at tech-software.net> wrote:
>> 
>>    What is “Pas”
>> 
>>    Whats coming ?
>> 
>>    *From:*OZAPRS [mailto:ozaprs-bounces at aprs.net.au] *On Behalf Of
>>    *Matthew Cook
>>    *Sent:* Monday, 18 December 2017 9:22 AM
>>    *To:* Australian APRS Users <ozaprs at aprs.net.au>
>>    *Subject:* Re: [OZAPRS] HF APRS
>> 
>>    I'd wait until early next year and see what's coming in terms of
>>    HF ARRS, plans are a foot.
>> 
>>    73
>> 
>>    Matthew
>> 
>>    VK5ZM
>> 
>>    On 18 December 2017 at 09:48, Robert <rbaker at bigpond.com> wrote:
>> 
>>        Hi All.
>> 
>>        Just a quick question on HF APRS.
>> 
>>        I have seen people chatting about modified FSK modem used
>>        directly onto Pas. My question is do I use these modified
>>        modems when I directly use say IC-706 mk2, or will a TT4,
>>        Opentracker do the job.
>> 
>>        Thanks in advance.
>> 
>>        Cheers
>> 
>>        Robert
>> 
>> 
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