Re: [IRCA] West Coast TPs Sept 19

[Scott Fybush <scott@xxxxxxxxxx>]

On 9/19/2018 4:26 PM, Chris Kadlec wrote:

> Henan often interfered with it at night and Iâd often hear 972 Pyongyang from atop the >skyscrapers downtown (like with many stations, I could only hear them atop the towers >*shrugs* - even though people say things like height make no difference with AM,  >something must explain that; perhaps steel conducts signals).

I don't think you're crazy here.

Here's what I think might have been happening: if you're in a crowded 
downtown of a big city like Seoul, at ground level you're probably in a 
somewhat effective Faraday cage. A 300-meter-wavelength signal is going 
to have a hard time penetrating a downtown street grid where the 
buildings are only 20 or 30 meters apart from each other and hundreds of 
meters tall.

Get on top of those buildings and you're out of the Faraday cage. The 
signals are still being conducted along ground (and perhaps up the steel 
of the buildings to your radio) rather than through skywave - but up on 
the roof you're not within the giant steel city grid that attenuates the 
long wavelengths of MW radio.

And we've known for 90+ years that steel building frames can have 
effects on MW signals - go all the way back to 1922, when AT&T started 
its station WBAY at one of its buildings in Lower Manhattan, only to 
discover the building frame itself was resonant at WBAY's 360 meter 
wavelength, causing it to absorb much of the transmitted signal. They 
had another station, WEAF, at a different location that worked better 
and they moved their programming over there.

(We had a similar situation in 1922 here in Rochester - the Times-Union 
newspaper put WHQ radio on the air in March and found its building 
absorbed too much of the signal from the rooftop antenna, so they shut 
it down and sold the license to George Eastman of Kodak fame, who 
restarted it later that same year as WHAM.)

s
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