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Star 100.7 on 98.5 102.9 103.1 what gives ???

X

xm41

The other night while driving in the South Hills listening to 103.1 KVE something was cutting in and out causing interference. I just thought it was fluke winter skip of some sort. Today going to the South Side I had the same problem. When I tuned down to 102.9 there was star 100.7 loud and clear. As I got deeper into the South Side where KVE had a poor signal Star was on 103.1 too. Scanning the dial I also found them on 98.5.

At my home by Century 3 Mall with a rooftop antenna and a rotor I can get Star clearly on all three frequencies in addition to 100.7.
 
I used to have a Pontiac where at one point the electronics in the car radio tuner
began to crap out on me. It would just arbitrarily start scanning around, stopping on
whatever station struck it's fancy. Initially the digital display would move too, but as
it got worse eventually it would stay on a particular number when in reality the tuner
was hopping around to other stations. Had to have it replaced at that point.
 
xm41 said:
The other night while driving in the South Hills listening to 103.1 KVE something was cutting in and out causing interference. I just thought it was fluke winter skip of some sort. Today going to the South Side I had the same problem. When I tuned down to 102.9 there was star 100.7 loud and clear. As I got deeper into the South Side where KVE had a poor signal Star was on 103.1 too. Scanning the dial I also found them on 98.5.

At my home by Century 3 Mall with a rooftop antenna and a rotor I can get Star clearly on all three frequencies in addition to 100.7.
Click to expand...

When you are line-of-sight to the tower, in close proximity to two or more stations, sometimes you get signals showing up in weird places. I'm not exactly sure of why the math works, but as a for instance, 100.7 - 98.3 = 2.4, and 100.7 +2.4 = 103.1. I believe 98.3 and 100.7 are on the same stick.

The 98.5 and 102.9 locations probably result from interaction with another signal or signals... in the South Hills, the 98.5 repeater from wherever it is might be the issue, because the difference from Star is 2.2 in each direction.

When I lived in Florida, there's a spot in Jacksonville that's an antenna farm for most of the stations in the market. When you drove past it, all of them came in at once on 100.7.
 
I used to live in the West End of Washington, PA and literally at this house, on my stereos you could literally only get WXJX (now WNJR) and WJPA, and they showed up all over the dial, preventing any chance of getting a Pittsburgh or other city's station. I always wondered how that worked, I've had that happen other places, but never as severe as it was in that house.
 
You were probably on a line directly between the two transmitters, so the other signals from further distances were overriden by the locals.
 
Your receiver was probably experiencing front end overload. The first amplification stage of a receiver is supposed to filter out all but the desired signal. But a very strong signal can overload the filter, and enter the first mixer directly. Cutting corners in the receiver design is the likely cause.

The other problem that's been described is called intermodulation. Basically, when two or more signals are present in a device, the output will contain both of those signals, plus the sum of the two, plus the difference of the two. Sometimes this is intentional (it's how the RF signal is converted to lower frequencies, for example), but it can also occur by accident. Corroded antenna or ground connections (or even poorly grounded metal gutters) can generate intermod. Since the mixing can involve not just the fundamental frequencies, but the harmonics as well (such as f1 + 2*f2, 2*f1 - f2, etc.), it can be a nasty problem to resolve.
 
dB said:
Your receiver was probably experiencing front end overload. The first amplification stage of a receiver is supposed to filter out all but the desired signal. But a very strong signal can overload the filter, and enter the first mixer directly. Cutting corners in the receiver design is the likely cause.

The other problem that's been described is called intermodulation. Basically, when two or more signals are present in a device, the output will contain both of those signals, plus the sum of the two, plus the difference of the two. Sometimes this is intentional (it's how the RF signal is converted to lower frequencies, for example), but it can also occur by accident. Corroded antenna or ground connections (or even poorly grounded metal gutters) can generate intermod. Since the mixing can involve not just the fundamental frequencies, but the harmonics as well (such as f1 + 2*f2, 2*f1 - f2, etc.), it can be a nasty problem to resolve.
Click to expand...

Yes, the malfunction in my Pontiac car stereo was explained to me as being along these lines.
 
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