--- In digitalradio@yahoogroups.com, Rick <[EMAIL PROTECTED]> wrote: > > Today the filter is often in the software program you are running on > your computer and it no longer matters what the tones are. You move the > cursor along the waterfall to place your signal or to decode the signal > and the mark tone may be 500 Hz, 1214 Hz, 2001Hz, but it could even be > 2125 Hz if you so choose and want to tune the rig so that the tone is at > that point. But it is not necessary to do this as long as the > relationship (the shift) remains proper at 170 Hz for most cases, and > with the mark tone high, as it relates to FSK. With AFSK and using a > different sideband things are a bit reversed, but as I mentioned > earlier, the programmers have mostly standardized on leaving the rig on > USB if using AFSK and they make the tones work correctly as if you were > actually transmitting FSK with mark high. > > 73, > > Rick, KV9U
Sure Rick, But people should know what happened in the past, otherwise they use a soundcard mode today with their 2.4 KHZ SSB filter and they expect all the filtering to be done from the soundcard, which is impossible due to the AGC effect. Some even use the 2.4 KHZ filter to copy 20 PSK31 stations and then they complain about adjacent interference!!! Really if one wants to have a decent QSO he/she must use a marrow filter and of course must know a bit of history and how to use such a narrow filter. I think the worst thing that ever happened to digital programs was the ability to move your cursor along the waterfall and think that anyone else with a stronger signal is QRMing your QSO!!! Maybe because nobody has ever bothered to tell the newer hams how did RTTY used to be in the past. And don't forget that really it does not matter if you use USB or LSB and you can always flick the REVERSE SWITCH. This is true for all narrow digital modes with the exception of QPSK31. In spread spectrum modes only, it is important for everybody to use the same sideband, i.e. for PACTOR 3 everybody uses USB. I believe the same is true for the rest of the wide modes. 73 de Demetre SV1UY
