Your comments are excellent. The only nitpick I would have is that I (and I emphasize the word I) don't know that the average ham tranceiver can even meet the constraints imposed by the ionsphere. This means less than optimum operation regardless of conditions. I know from experience trying to build transmitters and receivers, that it is difficult to meet some of the conditions needed to achieve optimum results. I don't have a lot of faith that the ham manufacturers you mention have done this in what really are very inexpensive radios. Even less faith that everyone periodically does detailed maintenance checks to insure that everything is operating as designed. Jim WA0LYK --- In [email protected], Vojtìch Bubník <[EMAIL PROTECTED]> wrote: > > Hi gang. > > The whole group delay fuss is pointless in my opinion because of the constraints that are put on the operating modes by our lovely ionosphere. I do not think that group delay is an issue at 100Bd symbol speed. > > The flattness of the passband is more an issue but it is something that the modems must deal with because of ionosphere fading anyway. > > There is one real issue - linearity of the whole transmitter - ionosphere - receiver chain. If more subcarriers are modulated, their mixing products will overlap if the chain is not linear, delivering considerable noise like products to the decoder. > > Thinking about the multi tone modes. Their average output power is considerably lower than if a single carrier mode like PSK31, RTTY or MFSK16 is used. Remember the average power of voice. One will never reach 100W average transmitted power with a 100W transmitter, but it is certainly possible with RTTY. One would need to create a linear transceiver with extremly high peak power to excercise 100W lot-of-tones digital mode. That is the reason why MFSK16 or PSK31 really shine with our YaeComWood 100W transceivers, because these single carrier modes utilize most of the power the transceivers are able to emit. > > 73, Vojtech OK1IAK >
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