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Possible, but kind of unlikely that it's related to that station. I
suspect all AM stations come in a bit louder over the bridge, and
that might make for an interesting test. Could just be a difference
in what appears to be ground to the car's electrically very short
I have a vague recollection of a similar effect from the deep past,
but can't quite place it. Now it will keep my up all night trying
to figure it out.
Jef - N5JEF wrote:
Just a thought. Could the bridge be acting as a
kind of travelling wave antenna, like a Beverage, and
re-radiating to the vehicle driving across...?
On Sun, May 2, 2021 at 9:10 AM
Jef Allbright <jef@...
Interesting question. Think I'll try to check it out.
Foresthill Fire District has an emergency radio operating
on 1020 AM under TIS
rules. The usual distance/signal falloff has been noted
in contour mapping.
Note, no spectrum analyzer on hand, just receivers with
dBu/v readings. Power is 4 Watts CW, but with 90% mod
when messages are played;
PEP 7-8 watts estimated (simple power meter) Inital setup
of the transmitter field density
is 2mv/.93 miles. Antenna is at 3200 MSL, in downtown
However, it was noted that the signal was higher, and
obtained receiver quieting
while crossing the Foresthill Bridge at about 15 miles
distance. From that point towards
Foresthill, the usual PGE, growlights and cable system
noises interfere as expected while running at
this low power level. Why does it sound so good there?
Is it the bridge structure and groundwave?
Take a crack at this one Extra Class!