On Dec 6, 2013, at 8:35 PM, Bill Turner wrote: > Spark gap transmitters only. Gonna be tough to generate a frequency shift carrier with spark gaps, though :-). However, if it is going to be true retro (pre-1956 FCC rules), you must also use 850 Hz shift. Since there are going to be only 5 contestants, this won't be an undue burden on spectrum usage. 73 Chen, W7AY