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Complete silence

V

vchimpanzee

30 miles southeast of a 1000-watt station at 1280 I pass a 1000-watt station at 1010 and the radio just goes silent, at least during the day. at night I hear distant stations. As I drive away from the transmitter the signal comes back.

My aunt lives near the 1010 tower and I heard what turned out to be the station at 1010 on a radio in her house I turned to 1280. One would think the same thing would happen in the car.
 
This might help explain what's happening:

Blocking/Desense
Desense is caused when a powerful signal drives the front end amplifier out of its linear region. As long as none of the signals entering a radio saturate the front end, things are OK. When one signal rises above a certain point, weaker signals begin to be attenuated, this is known as desensing. When this gets out of hand, complete blocking occurs. All radios will suffer from desense given a strong enough local signal. The signal causing the desense is usually not heard in the radio. http://www.scanstar.com/info/appnote2.htm
 
Car radios don't have a real tuned RF amplifier on AM anymore, and haven't for 25 years.
A real tuned circuit on on the antenna input is the only way to keep the mixer from overloading on the undesired signal.
Proper AM engineering is one tuned circuit before amplification, then one tuned circuit after, going into the mixer stage.
Digitally tuned radios usually dispense with the first step, and send the incoming signal straight to the mixer.
They do use a varactor diode as a capacitor to "tune" the loopstick antenna, but this is not very sensitive, and has no
chance of avoiding desensing overload. Such radios also often have poor AGC response, where the AGC may respond to
signals outside the desired (audible) passband.
 
This happens to me on I-65 in Columbus Indiana. I lose all the Louisville and Indianapolis signals for about 2 miles. This used to be an issue on I-640 in Knoxville Tennessee, but they seemed to have fixed this problem around 1994 or so,, or else newer radios are just made better. I dont recall the Indianapolis and Louisville stations having problems in Columbus Indiana back in the 80s, but their are a ton more stations and sticks in this area now.
 
I also noticed it driving on I-69 on the east side of Flint, Michigan.
The tower for WWCK-AM 1570 is right next to the road....very close!
I would often drive by it and think it was actually too close to traffic to be
safe. Even though it is only 1kW it always wreaked havoc until I cleared
the hockey arena.
 
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