Hi guys, Built a link radio out of a MASTR II mobile a while back. 444.575 TX, 447.575 RX.
It is NOT duplexed and the RX section turns off during TX, just a normal MASTR II mobile setup. The only modification done was to by-pass the PA and run the exciter output over to the Low-Pass Filter board in the PA section directly -- didn't need much power to make this link work with a 6 or 7 element yagi mounted outside, pointed at the repeater it's linking into. After having the link installed in my basement for a few days, I realized that it's throwing a fairly strong dead carrier on VHF at 145.460 or thereabouts, but ONLY when it's sitting idle in Receive. When the radio is transmitting the carrier generated by the receiver disappears. It's not strong enough to receive it further than about one house away on an HT down the street, and I don't hear it one block over, but there in the house... permanent carrier on 145.46. (Unfortunately this is the output frequency of one of our club repeaters that's over 40 miles and behind a ridge from my house, and the repeater "loses" completely to the carrier coming from the link radio in the basement.) I attempted to figure out the mix math to see if that would be a "normal" thing to see when using that particular UHF RX frequency, but I'm honestly not very good at that. I figured I'd post and see if any of the list's gurus might have an explanation of why it might be doing this. Any thoughts? I might (just to see what happens) stuff the crystals in another MASTR II, tune it up, and see if the same thing happens, but if this could be explained mathematically, that would be more "interesting". Hmm, what other info might you need... ahh... thinking back, the crystals might not have been ordered with high-side injection... I'd have to look at the ICM packing sheet, and it's at home. Nate WY0X
