The original question, as I recall, "how do we ground an antenna sitting on
the dirt?"
First, what configuration is the antenna? A tower has specific
requirements, a vertical requires a different method, a dipole or beam
another, and inverted L still another. In other words, isn't quite that
simple.
A vertical - A driven ground rod at its base and multiple radials extending
out at a depth of 6" or less. Radials ideally should be 1/4 wavelength and
the quantity, over about 65 yields little return on efforts. Usually 8 to 20
is a good starting number. Lightning protection is required at the point
where the feedlline enters the structure. This should be a suitable
protection device and driven ground.
A dipole or beam - No ground for the antenna required. But its supporting
structure may require a grounding system. Lightning protection is required
at the point the feedlline enters the structure.
A inverted L - A good radial system at the base of the supporting structure
and lightning protection is required at the point the feedline enters the
structure.
NOTE: Any driven ground or grounds MUST be bonded back to the AC mains
ground at the service entrance. This bond should run around the perimeter
of the structure and never under or through the structure.
Now the question of station equipment grounding. If the antenna presents
anywhere near a suitable load, and the feedline from the transmitter is
coax, then no ground is required for the equipment other than the safety
ground as prescribed by the National Electrical Code. i.e. 3 rd pin ground.
If the feedline is balanced, that is reasonability balanced to within 10% or
less, again no equipment ground is needed, other than the safety ground as
prescribed by the National Electrical Code.
If one is operating an end fed wire direct to the station equipment then a
very robust and complete ground system is required in as much as the
transmitter is, in effect, in series with the antenna. In general, we do
not use this method with today's equipment.
Just remember, the antenna provides a load for the transmitter and it is
this antenna that works against earth which we often confuse incorrectly as
ground. Ground is a zero voltage point.
73
Bob, K4TAX
----- Original Message -----
From: "George Fritkin via TenTec" <tentec@contesting.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Sunday, May 18, 2014 5:14 PM
Subject: Re: [TenTec] Grounds
Correct. The body/airframe/copperplate on a boat is the other half of the
antenna. This is why a dipole fed thru a balun and resonate makes the
most trouble free antenna. It contains a resonate both sides of the
antenna. There should be no feed line radiation. (fingers crossed).
Then a ground is superfluous. Of course you must have a good ac ground
unless you like the little tingles when touching different equipment
George, W6GF
Sent from my iPad
On May 18, 2014, at 4:47 PM, "Bob McGraw - K4TAX" <RMcGraw@Blomand.net>
wrote:
Same way a mobile antenna is ground referenced to a vehicle. The
airplane antenna uses the airframe as the reference ground.
73
Bob, K4TAX
----- Original Message ----- From: "george fritkin via TenTec"
<tentec@contesting.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Sunday, May 18, 2014 4:09 PM
Subject: Re: [TenTec] Grounds
Really Tell me how you "ground" an antenna in an airplane Carry a basket
full of dirt? These kind of articles written by pseudo engineers are not
helpful
George, W6GF
On Sunday, May 18, 2014 1:58 PM, Bob McGraw - K4TAX <RMcGraw@Blomand.net>
wrote:
This is an excellent written article and should be required reading for
every ham.
http://www.eham.net/articles/21383
73
Bob, K4TAX
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