RE-radiation question

[jtudor]

Does the FCC still regulate AM Re-Radiation, and if so, how do they monitor? Do they respond to complaints from the public?

To go along with that question, how can you determine if interference on a car radio is from re-radiation or a faulty radio?

In the Hickory, NC area, WHKY AM has increased power from 5000w to 50,000w. Ever since the increase, when I am driving in certain areas, close to power lines or poles with ground wires WHKY will cover up other stations I may be listening to. This is within about 2 - 3 miles of the array.

I have been out of broadcsting for about 11 years, but am a former CE and still have my first ticket.

Thanks for any information.

 

[Tom Wells]

Saw this posted last night and thought I'd let pros answer but none have, so here's my take:

Many of "proper" engineering niceties that the FCC required of AM broadcast have gone by the wayside.

New nearby structures of size to affect an AM pattern might get their attention if the station complained, but re-radiation via power lines
is not likely to be taken into consideration, even if the situation is new due to higher levels.

This sort of modulation may or may not be "in the radio".
Most new car radios do not have a proper RF preselect stage ahead of the mixer, because.....well, I can't figure out for the life
of me why they don't anymore, but they don't. So if the WHKY at its proper frequency can walk into the mixer, you will hear it along
with the station you want. I presume blank frequencies just adjacent do not have WHKY on them. Correct?
If so this is mixer intermodulation, and the only thing that can be done is to add selectivity.
The manufacturers presume most peole won't be driving around in such strong fields enough for them to
put a preselector in for the AM. It's also the proper place to point out that vacuum tube detectors (superhet mixer) do not
suffer nearly as much from this type of intermod, as AVC action is far more effective in preventing it in a tube than a transistor.

For a proper test you will need a good portable known to have an RF peselector stage, such as a GE superradio.
You will likely not hear the amount of the 50kw station as before.
Check for mixing with the loop-tick antenna in the radio parallel to the overwiring, and also check perpendicular.
The mixing will probably be less, and vary with angle.
If the mixing is constant, that would mean both stations would have to put a pretty good signal into the wire,
and this is less likely.

There are other scenarios that could exist, but since you're talking about 2-3 miles, it's probably not
some kind of A-B= image frequency, or a harmonic etc.

If you drive in real close to the array of WHKY, how wide does it "swamp out" on the dial?
A good radio with a preselector stage will widen out but keep it with a few 10's of khz.
With what's a normal radio these days, such a strong signal may wipe out one quarter to one third of the dial.