Re: [IRCA] [NRC-AM] Re: WGN Xmtr. Maintenance Period

["Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>]

>I guess what I'm simply failing to understand and if someone
>can kindly understand it without biting my head off... why
>would one station 1/2 mile away cause a hotspot for another
>and cause another station to sign off?

An antenna picks up a certain amount of power and sends it to a receiver, and it's turned into audio.  The power received is so far below the sensory threshold that you don't notice it when you touch the wire.

Now, get a tall tower (antenna) in close proximity to another source (power) and it will gather an appreciable amount of that power.  Enough to present a voltage large enough to feel, or maybe to cause injury.

You want a small demonstration?  Take an ordinary 40w fluorescent lamp and walk out next to your tower when it's on the air.  If you put that lamp next to the tower, it will light up in your hand.  Don't touch the metal ends with either your hand or to the tower.

Since the two Chicago stations are very close, and have tall and efficient "gatherers", there can be a dangerous amount of voltage induced in one tower from the other.  I would bet they have traps in their tuning units to keep the other signal out of their transmitter.  It could cause serious intermodulation products.  Such as (720 * 2) +/- 780 or (780 * 2) +/- 720.  I'd bet something shows up on 660 and 840, to name two likely spots.

Craig Healy
Providence, RI




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