I'm not sure you can simply use a frequency generator. Remember, what we are talking about are in essence, pulses, that is tone pulses throughout the audio passband. Perhaps one could use a pulse generator with a one, or ten, or 100 millisecond pulse at every 100 Hz from 300 to 3000 Hz at a substantial number of frequencies on each band to evaluate the overall performance. At the same time, monitor the RF output waveform to see what smearing in both the frequency and time domains occur. I suspect you'll see a substantial smearing of the pulse width and substantial time delays. As far as measuring phase variances, more sophisticated methods will probably be needed. Also, to establish any good baseline would require measuring a pretty large number of common ham radios. Jim WA0LYK --- In digitalradio@yahoogroups.com, Mark Miller <[EMAIL PROTECTED]> wrote: > > Rick, > > Yes group delay is an issue, but with adaptive training this too can be > overcome. Sound cards, or external modems using DSP or preferably FPGA's > would be a fine compliment to most amateur gear. The SDR (software defined > radio) that Jose mentioned will be the best solution going forward for more > exotic modems. These modems would be an integral part of the radio. > > I was looking for a good way to test group delay, and was thinking of > generating an FM signal with 3 to 5 KHz deviation and looking for an > envelope at the output of the receiver. Does that sound ok? The signal > generator is an HP 5640B. > > 73, > > Mark N5RFX > > >Another thing that I came across in my web searching was that amateur > >equipment generally has group delays that make it difficult to even > >employ some of the modems we have been discussing. >
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