[OZAPRS] DSP modems.

[Steve]

The DSP modem Mike supplied a link to has this fantastic capability:-
"The DSP automatically processes a frequency range of +- 400 Hz looking 
for 300 bd transmissions and receives all detected signals in PARALLEL. 
No exact tuning by the user is necessary any more, but always perfect 
reception! Very important feature for automatically operating HF APRS 
gateways."

Is this the only unit able to make such a claim?

On my HF I-Gate I'm currently trying to work out which is the more 
reliable out of my old MFJ-1270B, the Windows MixW and finally the 
Unix/Linux "soundmodem". In fact, I usually run a couple of these 
together, from the same audio (Codan 8525B) to aid doing my comparisons. 
(note soundmodem is a pain as it needs the tones to be no more than 4 
times the data rate).
While they all work OK, none of these are very frequency tolerant at all 
- even though MixW and soundmodem have plenty of CPU power available to 
them (obviously the code isn't up to the same "DSP" capability as the 
SCS units).
As I have a waterfall display running on 30M APRS (via MixW), I can see 
that plenty of signals that are nice and strong not get decoded by my 
station simply because they're slightly off from the majority of the 
other stations I see. I do a visual averaging of all the signals I see 
and try and set my station's RX frequency such that I can decode as many 
as possible. It's touchy, and I miss a few stations doing this.

So, does anyone know of any other software that may perform better (it'd 
need to be able to provide a virtual serial port though)?

Maybe I could run three instances of soundmodem and stagger their RX 
tones across 50Hz or so!

Maybe I should stop being cheap and put an order in for the product Mike 
has linked to below?

Thanks for any thoughts,

Steve (VK2ZSZ)


On 06/10/2011 10:00 PM, OE3MZC Mike wrote:
> Hi Steve,
> usually on a sailing boat on sea (salt) water you will have much better
> efficiency of your "mobile" antenna,
> which will give the gain you need to make 5W QRP work...
> compared to a mobile antenna on a 4x4 in the dry dessert.
>
> Single hop - I meant a single ionosphere hop, because of additional losses
> on ground reflection with multi hop.
> See info abt DSP-TNC at
> http://www.scs-ptc.com/shop/products/modems/tracker-dsp-tnc
>
> Vy 73 de Mike, OE3MZC