Maybe Canadians did RTTY/digital data differently than the rest of the world?
John's comment that there is a tradition that when a frequency is given that it means VFO frequency just is not true from any historical perspective. It may be that he never operated RTTY which is the historical beginning of what most of us consider to be digital operation and typically the mark frequency was often given. When an operator gave a frequency it was the actual frequency they were operating. If an operator was using AFSK, they would have to calculate the difference to put themselves on the correct frequency. This was absolutely critical when using autostart. And it was also savvy and knowledgeable operating. The truth is that no one used the AFSK dial frequency to indicate their digital frequency unless they did not understand that running AFSK is going to give you a significantly different transmission frequency than those who specified the actual mark, space, or center frequency they were operating. There are a few rigs that will display space or mark tones for RTTY operation. Also, some digital programs, such as WinWarbler, display the actual frequency above the waterfall assuming you have rig control. If you have used this program, you will note that when you set your frequency on the nearest KHz, it will display that frequency on the left most part of the waterfall and the frequencies above that point if using USB. So, if you set the program to RTTY, it has the standard 2125/2295 Hz points marked on the waterfall which has been the standard for the high tone pair for mark and space for many decades. If you wanted to tune in those tones at their standard audio frequency, at an RF frequency of 14109.5, you would need to set your dial frequency at 14107.30. This was often needed because the most U.S. TU's required the tone pair of 2125/2295 Hz in order to insure minimal chance of sending harmonics from the rig. It sounds complicated, but with WinWarbler it does not require any calculations since you just center the tones in the marked area. For PSK31, assuming you want to center a 14109.5 kHz signal at 1500 Hz, you would of course set your rig to 14.108.0 and you would be at the correct frequency. When I tell someone that I am transmitting on 14109.5, I always put my cursor on the 1500 Hz point on the waterfall to center the mode, and move my VFO to 14108.0 so that I really have my signal on 14109.5. When John, VE5MU, claims to be transmitting on 14109.5, he is actually centering his transmitting frequency on 14.110. While you may be able to tune around to find him, I think that most reasonable and hopefully savvy digital operators would agree that knowing his actual frequency is much better. It is probably not too unfair to say that the increased use of AFSK has made a number of hams confused about what frequency they were on. Even voice can be an issue when we consider centered frequencies, and not dial frequency. Look what has to be done just to operate USB voice modes on 60 meters. We are given the center frequency and have to calculate our frequency from that point to work with our dial frequency readout. My equipment has optimum filtering when operating in SSB digital modes only when I center the frequency at 1500 Hz. Therefore, I move my VFO appropriately if I hear something that I want to decode. I only move around the waterfall for casual checking of signals or if they are very strong and I am betting that I won't need any filtering in place. I admit that there have been a number of times that I was in QSO with someone away from the optimum 1500 Hz point and some QRM appeared that I could not filter out. A truly experienced digital operator would not expect another operator to find them "somewhere" away from the dial frequency when they can just give them the frequency. KV9U John Bradley wrote: >I know this argument has been beaten to death before,but here it goes again. I >think all of us who are using digital modes understand >the offset concept. > >If you specify a VFO frequency, this is a good starting point for finding the >other station. With the number of modes out >that allow tuning the offset, the offset can vary from under 500hz to 2000hz >and still stay within the bandpass of most rigs. > >If I am in QSO sequentially with several other stations, I would be using the >tunable offset to receive the signal as best I can, therefore the >offset is not fixed, but my VFO frequency is. In a similar fashion I may have >tuned the offset to avoid a CW station, again staying >at the same VFO frequency. > >Specifing a VFO frequency establishes a point to look up from . Most >experienced operators would tune their offsets from 500hz up to 2000hz >looking for the signal. And usually once you set the VFO frequency, the signal >you are looking for is pretty obvious. > >Traditionally, when a frequency is given that means VFO frequency, and not >something that includes the offset. This is simple, and has been is >use for a long time. > >In other words if it ain't broke, don't fix it. > >Regarding the IARU guard frequencies, there are not a lot of users out there, >hopefully more with the recent regulation changes in the US. >I would hope that good operating practice among the ALE users would ulitlize >the 14100.5 frequency only when absolutely needed, >otherwise they will come to be regarded with the same love and respect the >pactor folks are ...... > > >John >VE5MU > > >
