[OZAPRS] DSP modems.
Steve
stevez at tpg.com.au
Sat Jun 11 07:56:41 EST 2011
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
More information about the OZAPRS
mailing list