Propagation delay in the coax. Get a dual trace oscilloscope and feed it with a 10 MHz GPS, off of a Tee and into 2 different lengths of coax.
I could see the DC offset thing if the audio was coupled with a 1uF cap at one site and a 0.1uF at the other. > Maybe I'm missing something here, but how the heck would the length of the > cable from the reference oscillator to the transmitter/exciter matter? It's > just the frequency reference (10 MHz or whatever) for the synthesizer; it > has no effect on delay, phase, amplitude response, or anything else related > to the modulated audio. > >> Also if these are VHF it could be that the reference frequency >> (channel spacing) is 5 kHz, if that is the case a harmonic of a paging >> tone might get past the audio pass band filtering 300 - 3000 Hz >> typically and is fooling the PLL divider. > > This seems like a longshot. I think Bill's original guess is most likely on > the right track - a DC offset problem. I'm assuming the transmitters are > being modulated through a non-DC-coupled input to the modulator? Maybe look > for a coupling cap with high leakage. Another thought is asymmetrical > clipping of the audio. > > --- Jeff WN3A > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > >
