[UK-CONTEST] Data contests

[Andy Swiffin]

>>> On 01/02/2011 at 13:02, in message <4D48044E.1020104 at btinternet.com>, David
G3YYD <g3yyd at btinternet.com> wrote:
> Andy
> 
> Fair question. Simple answer my own experience.
>...
> My home made DSP decoder can copy on a single tone unlike MMTTY with 
> about a tenth of the processor load. Overall performance is very close 
> to optimised MMTTY sometimes better sometimes worse depending on the 
> type of QSB. The AFC is better than MMTTY and the filters are already 
> optimised so no fiddling around with values. Judging by the available 
> variables in MMTTY the "circuit" architecture used is non-optimum. If 
> anyone is interested in my decoder's architecture please contact me off 
> list. I did it as a learning project in DSP Windows programming. The 
> hardest part was understanding how Windows works rather than the DSP 
> bit. Really exercised the "little grey cells" to borrow a phrase and was 
> great fun. I did have a really excellent tutor, Peter G3PLX.

Thanks for that,  interesting.

My own use is far less sophisticated.   I just use my laptop,  one radio and fsk on tx,   as it all seems OK enough frequency wise I'll leave it as is for now.

Talking of decoding performance, other RTTYers may be interested in the new profile which appeared with the latest version of mmtty.    I hadn't upgraded for a while but I heard about it on the rtty contesting list so upgraded to get it.   Produced by Dave AA6YQ,  some discussion on it starts here: http://lists.contesting.com/pipermail/rtty/2011-January/033111.html  but it has cropped up later in the month too.    It does require quite tight frequency control as its filter is narrow and steep- which is why I was quite concerned to hear about a possible discrepancy with sampling rate!! 

I used it during BARTG and found it quite effective.    That is, once I'd discovered the other setting on my laptop that some other application had "tweaked" which had completely trashed my copying entirely!!  

73
Andy
gm8oeg



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