jeh@simpact.com (01/18/90)
The discussion about blockage of FM vs. AM broadcasts in tunnels reminds
me of a question I've been meaning to ask.
While in Boston a few years ago, I drove through some tunnel or other in
my rental car (AM radio only). The station I'd been listening to was blocked,
which I expected. What I didn't expect was that the radio began picking up
something that called itself "Tunnel Radio", a series of advertisements.
What was VERY strange was that "Tunnel Radio" appeared EVERYWHERE on the
AM dial; the tuning knob on the radio might as well have been disconnected,
for all the effect it had.
How does/did this work? Are they broadcasting on the radio's IF frequency
(455 KHz)? That would explain why the tuning knob had no effect, but it
seems to me that it would take one hell of a lot of signal.
--- Jamie Hanrahan, Simpact Associates, San Diego CA
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