[Lowfer] No luck with - JH

[JD]

>>>Some of the older literature really isn't all that useful - Laporte wrote
>>>mostly of large commercial/government installations, and George Brown did
>>>most of his work just below 80 meters.

True.  And at least one of the QEX articles was all about experiments at 10
meters, which were not at all scalable to the AM band where the author
suggested (at great length) that the FCC needs to re-evaluate the
engineering practice for grounds, based of his results.  I wrote to the
editor about that, and he thought I ought to expound the point in print, but
I got sidetracked and never got around to giving them permission to publish.
Some of the concepts are probably even less applicable farther down at LF.

If one gets down to the fundamentals of what you're trying to accomplish
with grounding for an electrically short vertical LF transmit antenna, the
first and foremost task is to provide a low loss return path for current
where the field is strongest and the current density in the earth is
greatest, near the antenna.

For super-short antennas, this distance is not a quarter wavelngth.
(Resonance is an irrelevant concept for buried radials at frequencies where
the surrounding medium is nearly pure resistance, anyway.)  As I mentioned
on the LW Message Board, the radius of the reactive region for our very
small antennas will be somewhat longer than the height of the antenna,
thanks to fringing effects.  That's where the bulk of R_loss will be
found...not out to 1/4 wavelength, nor even to the usual 1/(2*pi) definition
for near-field.

Now, you might be able to *slightly* improve the launching of your signal if
you also keep loss low in the transition region, which extends out farther
than the reactive zone, but this is where practicality often has to take
over.  As LowFER pioneers like Mike Mideke and others pointed out several
times based on their own practical comparisons, if you are limited by space
or materials to a choice of either a few long radials, or a greater number
of short ones ("short" meaning on the same order as your antenna height),
then the more the merrier.  Branching off at angles from the main radials
with shorter ones, part way out along the main radials, is another way of
filling gaps in the ground field that can be reasonably conservative of
limited materials.

In short, the more you can make the region under your antenna approximate a
nice conductive plate of metal to the displacement current--and less like a
huge mesh of resistors branching out everywhere--the lower the loss will be.
It's possible to do this to the point of overkill, of course, but not many
of us are that fortunate. :)

And John H., don't worry: your "ground lead" is just that...the lead that
connects to your ground, not what's in the earth.  I can feel very confident
about that view because of a lot of reading I've been doing lately (mostly
of material I'd really rather not have had to slog through) in connection
with so-called Part 15 microbroadcasters, and FCC enforcement actions
concerning them.

There has been a substantial crackdown on the "whip on a mast" AM
installations that a lot of those were using, where even some manufacturers
of certified transmitters had allegedly urged customers to put them on 50
foot grounded poles, metal billboards, water towers, etc.  Well, those
supports are just a form of extended (and excessive) ground lead, and that's
exactly what the FCC has been issuing citations for.  I've also read a
couple of notices concerning elevated counterpoise systems, which from one
viewpoint a person might well argue to be a substitute for ground; but the
FCC with equal technical legitimacy chooses to view them as part of an
asymmetrical dipole antenna, which therefore must be counted in the total
length.  So far, though, the FCC's enforcement folks have consistently
stopped measuring total length at the point where the ground lead enters the
earth.  Not once have I heard them questioning "how deep is that ground rod
buried" or "how far does that water pipe run?"  Ergo, I believe we can rest
assured that what's IN the ground IS the ground, and only the lead from our
transmitter to it need be of any concern.

Regards,
John D