[OZAPRS] DSP modems.

Ben Lindner vk5jfk at activ8.net.au
Sat Jun 11 09:11:56 EST 2011


Steve


Just buy yourself an early Xmas present and this will make you happy as 
a kid in a lolly shop. The Euro and our Dollar is quite reasonable at 
the moment.

cheers
Ben
VK5JFK



On 11/06/11 07:26, Steve wrote:
> 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
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