[BC] Part 15 LPAM Question?

[Dana Puopolo]

It's a gray area. I've installed several part 15 statems in colleges. They all
pass FCC muster. In these cases the transmitter case was bolted to the
structual members of the building. What's the 'ground lead' there? The length
of the bolt (about 1/2 inch) or the four story gym?

Has anyone used an emitter or source follower in a Part 15 transmitter to
match the (very low) impedance of a short antenna? Yes, I know their gain is
slightly less then unity, but the coil losses in a large network might be
more. 

-D



------ Original Message ------
Received: Sun, 10 Sep 2006 06:04:10 AM EDT
From: "Richard Fry" <rfry at adams.net>
To: "Broadcast List" <broadcast at radiolists.net>
Subject: [BC] Part 15 LPAM Question?

>I'd put a 102 inch CB whip (with spring) atop the cabinet,
>and stick the whole thing 25 feet in the air (preferably 25 feet
>above a nice steel frame building that the mounting pole
>is lightning grounded to with a nice wide strap).
>No "ground lead" would be used.
_______________

But in reality, conductors such as the building frame and the nice wide 
strap connected to the tx chassis by a low-Z path will become part of the 
Part 15 AM radiator length along with the 102" whip, and likely will 
radiate more field than the whip, itself.

So this system _would_ have a functional 25 foot ground lead, even if that 
isn't recognized at first.

RF 

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