On 12/31/2013 11:21 AM, Tom W8JI wrote:
I've never looked at the FT1000, but I doubt that is a clean system. It would still be like a SSB transmitter with audio signals if that is how they do it. It would be much better to actually shift a carrier, and not do the baseband audio signal run though a balanced modulator and then through a sideband filter.
AFAIK, all non-DSP rigs with synthesizers work this way. Assuming you want the output frequency to be derived from the master clock frequency, there is no easy way to shift an RF carrier. You can't use a free running oscillator, because it won't be derived from the master clock frequency. You can't switch between a mark synthesizer and a space synthesizer because of transients. If you try to key the programmed frequency of a BFO synthesizer, the PLL will probably go out of lock momentarily, producing garbage. Also, it may not be fast enough to keep up with RTTY. After considering all this (as a very experienced synthesizer designer) it is hard for me to blame the designers for using AFSK. I imagine I could make a synthesized RF FSK system if I wanted to go to enough trouble, but obviously Yaesu's resources were limited. Rick N6RK _________________ Topband Reflector Archives - http://www.contesting.com/_topband
