Are the cables coming from the GPS reference are the same length at both sites?
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. On Wed, Jun 23, 2010 at 1:01 PM, wmhpowell <[email protected]> wrote: > I'm looking for some Quantar "engineering level" help re: an > interesting simulcast issue. > I live in an area where I can hear several of high band our simulcast > Quantars. The whole thing was installed and set up by Motorola > including GPS stabilized time bases. > I'm monitoring with a true "monitor": wide band IF and little > limiting. > When the dispatcher drops a dead carrier I hear little in the way of > hetrodyne or "grunge" as it should be. > However, when the dispatcher drops alert tones I hear a hetrodyne > that decreases in frequency over the duration of the tone. > > My guess is that the tone is somehow pulling one of the VCOs in a > Quantar exciter because of a lack of DC restoration in the modulator: > a capacitor is charging and slightly shifting frequency. > > I consider this to be abnormal and undesirable behavior - especially > in a $y$tem of thi$ caliber. > > I haven't done any field tests yet. I suppose I can set up 2 service > monitors: one to receive in the AM mode and the other to provide a > reference carrier and then send tone to each transmitter, in turn. > That, at least would let me isolate the problem to one, two, ?? > radios. > > Has anyone else experienced a problem like this? > Any Motorola engineers out there? Our local tech is also baffled so > I'm reaching out for ideas. > Thanks, > Bill Powell > > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > >
