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Re: [TenTec] OT: Indoor Antenna

To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
Subject: Re: [TenTec] OT: Indoor Antenna
From: "Rick - NJ0IP / DJ0IP" <Rick@DJ0IP.de>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Thu, 2 Dec 2010 19:38:07 -0600
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>

I agree in spirit with what you say and having worked portable all the time
for nearly 50 years, I am a huge believer in the benefit of a quarter wave
counterpoise, but...

There are some interesting antennas I have been reading about in the "ARRL's
Wire Antenna Classics" book which require a terminating resistor at one end.

These go to a ground stake.  
That ground stake is not necessary for DC ground.
It seems to me, in this case, the ground stake is indeed an RF ground.


-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of Stuart Rohre
Sent: Thursday, December 02, 2010 6:44 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] OT: Indoor Antenna

Absolutely, you would need a counterpoise.  An eight foot ground wire 
would only function as a tuned RF conductor at 10m where it is a quarter 
wave long, but it would be high impedance at the shack most likely.
At any other band, the length of 8 feet is not enough of an RF resonant 
conductor nor of such a diameter, typically, to have low RF impedance.  
Ground rods are a DC and 60 Hz safety convention.  Most soil is very 
poor at best at RF frequencies.  Your counterpoise actually acts as an 
insulated antenna element, and does much more good for you, and balances 
the loaded antenna element, which is itself short for the purpose of 
being a radiator at a ham band frequency.

An old ham myth is that a ground rod is sufficient as an RF ground.  It 
should be used for a safety ground, but not relied upon for an RF 
ground. It may work if your local soil conditions are very conductive, 
but the whole interface of it to the soil and the soil itself is an 
inefficient RF element.
You don't have enough surface area on the typical rod to have low enough 
impedance at RF.

GL and 73,
Stuart Rohre

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