[TowerTalk] Anyone use a 120' qso king?
TexasRF at aol.com
TexasRF at aol.com
Fri Jan 24 11:38:54 EST 2014
One way of looking at radials with the ends grounded is as a transmission
line. The radial is one conductor and ground is the other conductor. A
ground rod essentially shorts the far end. With a radial length of 1/4
wavelength, the short reflects back as very high impedance. High impedance means
little current flow into the radial and that is opposite of what is needed.
Even shortened radials will suffer with reduced current flow.
In a message dated 1/24/2014 8:28:49 A.M. Pacific Standard Time,
jim at audiosystemsgroup.com writes:
On 1/23/2014 8:44 AM, Herbert Schonbohm wrote:
> Some would argue that putting ground rods at the end of radials
> doesn't really help.
Right. Really bad idea. We do NOT want current flowing in lossy earth.
The function of radials is to SHIELD the antenna from lossy earth and to
provide a return for antenna current and the fields the antenna
produces. Also, the end of the radial is a high impedance point. Adding
a ground rod messes up the current distribution on the radial, and
> In most cases you can do well, perhaps better with #12 or #14 THHN
> insulated wire laying on the ground. You will only then need about
> 90-100 feet for each radial due to the velocity factor of the wire
> itself. If you run out of space due to your lot size you can run the
> ends at right angles. It is important that the ends are not grounded.
> IMHO what you are trying to do is cause the ground system currents to
> travel in those wires rather than being dissipated in the earth thus
> improving the system efficiency. You can pin the wires down with large
> galvanized nails, , pounded into the ground after a single turn around
> them. (U clips are also available by the hundred lot from
> DX-Engineering) Normally after two weeks the sod will cover them and
> they will be invisible and allow the lawn mower to pass over without a
All of this is very good advice.On-ground radials are as good as buried
radials -- the only reason to bury them is to protect them from foot
traffic. In general, with on-ground radials, more is better and length
is not critical.
73, Jim K9YC
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