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
