rf ground....

To: mail11: ;
Subject: rf ground....
From: pierson-at-msd26.enet.dec-dot-com
Date: Tue, 24 Sep 96 12:30:17 EDT
Cc: pierson-at-msd26.enet.dec-dot-com


(No.  I STILL haven't found that test process....)

>The ideal counterpoise would be boring and threading a 1" diameter hole 
>in the deck of the battleship Missouri while at anchor in a nice salt 
>water port.  I don't think there would be a detectable difference even in 
>dry dock.

	Not Particularly Close.  8)>>

	Typical AM Transmitter grounding practice is a 1/4 wave radial
	(thats the length) every 5 degrees or so in a complete circle.
	Figger the 1/4 wave length for the operating frequency of the coil in
	question.....

	There is (was?) a transmitter in Florida (Not radio Marti, years before)
	with the tower on the end of a pier and the counterpoise/ground was
	the Atlantic Ocean.  Not Real Practical for the average coiler.

	(Hmmmm.  I wonder if there is a surplus, disused, island lighthouse
	available.)

On a more serious note, i don't think the FCC specifies ground goodness, per se.
They DO specify (or accept) specified coverage patterns, be they circular or
'directional'.  Predictability of THOSE requires a good (see above) RF Ground...

I once took an IEEE sponsored tour of the USN VLF transmitters, in Cutler,
Maine.  (can post longer description, but its not_tesla).  They can put out up
to about 2 MW _continuous_ at 24 KHz.  The ground system is described as
'chicken wire over the whole area (square mile or so) with the ends dipped into
the sea... 

	regards
	dwp