Hi Tony, I got the impression in talking to the WinDRM users on 7173 SSTV group, that it worked with lower than +10 dB S/N. Maybe around 7 dB?
The older programs used the RDFT protocol which did require around +10, and that is at least part of the reason for so rapidly abandoning RDFT based software and moving toward the OFDM type as found in WinDRM. I am not sure how RDFT works either, maybe it has a similar modulation scheme to OFDM? The audio quality is that "internet" sound that we used to get with low quality dial up speeds and is not unlike some cell phone connections. I am assuming this has a lot to do with the number of dropped packets. 73, Rick, KV9U KT2Q wrote: > Rick, > > WinDRM does need a fairly good SNR. The threshold > seems to be around 10db. Of course it's much > easier to achieve that on the upper HF bands so > it's usually not an issue there. On 40 meters and > below it seems that DVDRM mode does a better job > coping with QRN. > > It's not exactly hi-fi as you say, but it's > interesting to note that the decoded audio has a > range of about 4khz (see attached). The lows dip > way down and the high-end is slightly above 4000 > hertz. > > I guess you could say audio response is pretty > good when you consider the RF bandwidth is the > same as used for SSB! You'd need 4khz to duplicate > this with analog. > > Mel and I have fooled around with EQ a bit and you > can enhance the DV audio to sound > terrific, but the problem is getting software EQ's > to work simultaniously with WinDRM. An outboard > unit would work fine. > > Check with Mel about the DVDRM mode info... > > 73, Tony KT2Q > > >
