John,
Thankyou for the correction in the formula. In fact the 18-ohms
measured by the antenna analyzer is the total resistance and includes
both radiation resistance and ground resistance, so my numbers are
correct, just not my explanation of them.
This was done three years ago and I forgot some of it. Like others
have observed not something calculated everyday.
Direct measurement of radiation resistance is the difficult part, so
this provides the required calculation with the normal uncertainty of
antenna modeling.
One can understand the problem of installing a quarter-wave vertical
on 500-KHz which would be 415 foot tall. I do not have the resources
for really tall antenna (even 200-foot would be nice), so the top
loading of the inverted-L is one of the standard antenna for low-low
bands. Then one considers quarter-wave radials - you need some real estate!
Yet even with this obvious compromise my signal has been detected
2800 miles running only 4.15w ERP. The new ham band will likely only
permit 1w to 5w ERP so this is in the ball-park of what is possible.
73, Ed - KL7UW, WD2XSH/45
-----------------
From: KU4AF <[email protected]>
To: [email protected]
Subject: Re: [Elecraft] Random wires
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii
You're slightly more QRP than you think. Efficiency is radiation resistance
divided by total resistance (not ground resistance). So your calculation
should be:
73, Ed - KL7UW
http://www.kl7uw.com
[email protected]
"Kits made by KL7UW"
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