Any time you deal with the government, the rules are secondary to
what they want to see. What you learn to do, whether filing for type-
acceptance or doing a BC station, is do what they expect to hear.
If you do what they expect, you never get put through the ringer.
Part 73.189 (4)
"At the present development of the art, it is considered that where
a vertical radiator is employed with its base on the ground, the
ground system should consist of buried radial wires at least **one
fourth wavelength long**. There shall be as **many of** these
radials as evenly spaced as practicable and in **no event less than
90**." (120 radials of .35 to .4 wl and spaced 3 degrees is
considered an excellent ground...blah blah on and on)
This is the text that 120 radials 1/4 wl long came from. The FCC
just loves seeing 120 1/4 wl radials, and a ground system like that
will slide right through their reviews without raising any questions. If
you add a screen, even though it is only required on a voltage fed
antenna, it will slide through even better!
So to properly slide through the FCC, engineers have been
"trained" to use an (unnecessary) screen and 120 1/4 wl or longer
radials.
If you have less than 90 1/4 wl radials, a red flag pops up and they
make you prove it still works. If they don't see a screen, they want
to know if the antenna is really current fed (heaven help you if the
radiator is .3 wl tall instead of .25 wl and there is no screen). They
act like the applicant doesn't know what he is doing, and start
looking at everything closely. 120 radials at least 1/4 wl long and a
screen guarantees you pass that point without having to prove
anything, because they see "headroom" over the minimum and
think you are a conservative fellow who makes good solder
connections.
Kinda like counting chads in Florida.
73, Tom W8JI
w8ji@contesting.com
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