Topband: Broadband Inverted L

[Charlie Cunningham]

To elaborate a bit on Tom's point -14 ga wire would have approximately 0.4
uH/ft of inductance, so 40 feet of 14 ga wire would be around 16 uH with an
inductive reactance at 1.8 MHz of around j180 ohms.

Compare this with the radiation resistance of the 1/4 wave inverted L, of
perhaps 10-30 ohms resistive, and it becomes pretty clear that the 40'
"ground" wire is not really an effective RF ground for the antenna.
Furthermore, the displaced radial field is no longer beneath the antenna
where it needs to be to provide an image for the antenna fields. A 4' ground
rod, unless it's in salt water is not much of an RF ground either, so the
losses in the system as built are horrendous! Putting even a couple of
elevated resonant radials under the relocated inverted L should make a huge
difference!

73,
Charlie, K4OTV


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-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Tom W8JI
Sent: Thursday, November 20, 2014 2:18 PM
To: topband at contesting.com
Subject: Re: Topband: Broadband Inverted L

Ground systems cannot be evaluated or estimated by number of feet of wire,
just like they cannot be evaluated by SWR or bandwidth, but I'm sure we all
agree on this......

The single most important thing Joe said was:

<<<< The antenna feed point terminates at a four foot ground rod and then I
am running a number 14 wire from that ground rod to my existing radial
field. That run is about 40 feet. >>>>

Joes has virtually no ground at all on 160 meters, because his system's
ground connection to the radials is via a single #14 wire 40 feet long.

A 40 ft long wire laid on earth to the radials, even if Joe had 50 x 100 ft
radials, would almost certainly make the ground path impedance hundreds of
ohms.

Joe's antenna virtually doesn't have a ground connection to radials at all,
and this has almost nothing to do with the number of radials or type of
radials. It has to do with the 40ft long connection.

73 Tom


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