[Antennas] All You Ever Wanted To Know About A Hustler 5-BTV Vertical !

2003年2月26日 23:52:03 -0600

I agree with Hustler on insulated buried radials, although not for any
electrical reason. Nor do I believe that there is any electrical merit in
burying a radial wire.
Nope, the reasons are practical and cosmetic. A buried wire that is
uninsulated will eventually - might take 10 years, but eventually -
deteriorate unless buried in sand <g>. I made the serious error of laying in
60 radials under my vertical, each buried about 1" below the surface to
clear the mower, etc.. The error was in using "cheap" bare aluminum electric
fence wire. It lasted fine for a year or two but after that the soil
chemicals ate much of the radial field. So, I am a firm believer in
insulated wire for radials and for sealing any openings where moisture could
leak in and start corrosion.
The radials should present the lowest loss path possible in order to not
degrade the efficiency of the antenna installation. Wire size is almost
irrelevant since the total current divides more or less uniformly among the
total number of radials, so any one radial is carrying only a small
component of the total current. No. 18 solid insulated "bell wire" from Home
Depot is a fair buy. It comes in a three-strand twisted format such that
each wire figures to cost about three cents per foot. I use the larger #14
THHN house wire for antennas at 15ドル for 500 ft or again about three cents
per foot. The advantage of the smaller wire is ease of installation,
partially offset by the need to unwind it! <g>
As to burial, the whole idea of a radial field is to capture displacement
current being returned to the transmitter via the coax inner braid. We use
radials instead of relying upon the return currents passing through lossy
soil. So, to me, it makes little sense to intentionally bury those
current-collecting radials "under" the soil so that the displacement current
has to pass through it on the way to the radials. As to the electrical
facts, the skin effect at HF with soil is such that the return currents flow
to a depth of several feet depending upon the frequency, soil
characteristics, etc. So, while one can count on there being current in the
soil even at a considerable depth, it never really made sense to me for
amateurs to bury the radials a foot or so in the ground and introduce the
loss of that extra soil path. Commercial broadcast stations commonly bury
their radial fields to quite some depth, but I believe that this is
primarily to protect the wire from surface damage, such as plowed fields,
etc. Also at BC frequencies, skin depth current penetration is quite large.
Interesting things, radials - I still get a backache thinking about laying
in those 60 radials! <:} And a worse one thinking about replacing at least
part of them.
73/72, George
Amateur Radio W5YR - the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
"In the 57th year and it just keeps getting better!"
-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of W1GOR
Sent: Wednesday, February 26, 2003 9:14 PM
To: [email protected]
Subject: Re: [Antennas] All You Ever Wanted To Know About A Hustler
5-BTV Vertical !
Dan,
I agree with your comments regarding the elevated radials... However,
Hustler's instructions specify insulated buried radials. With the heavy
clay soils here, I really didn't want to do all of the work involved in
laying the radials more than ONCE...<grin>. The final result, using fully
insulated radials, and cut to the lengths listed in the instruction sheets,
is that the 6-BTV meets or exceeds Hustler's specifications. Ya jest
cain't ask fer moah, now kin ya...? A'yuh...!
73, Larry - W1GOR
----- Original Message -----
From: "Dan Richardson" <[email protected]>
To: "W1GOR" <[email protected]>; <[email protected]>
Sent: Wednesday, February 26, 2003 9:59 PM
Subject: Re: [Antennas] All You Ever Wanted To Know About A Hustler 5-BTV
Vertical !
> At 09:38 PM 2/26/2003 -0500, you wrote:
> >Dan,
> >
> >The installation instructions for the 4, 5, and 6-BTV antennas specify
fully
> >insulated radials. The best way to accomplish this, is to bury
insulated
> >wire and seal the outer end. Liquid insulation works very well. I've
got
> >a 6-BTV and installed 4 radials per band. Each radial is made of
insulated
> >14 AWG stranded wire. I chose a bright red wire that will show up well
> >against the green grass... Up here in Maine, frost heave occasionally
> >causes shallow-buried radials to creep to the surface during the spring
> >thaw. So far, I've avoided running over the red radials with my ride-on
> >lawnmower...
> >
> >73, Larry - W1GOR
>> Larry,
>> It is my understanding that elevated resonate radial systems would indeed
> need to be insulated, but that would require nothing more than not
> permitting the wires to touch anything and placing insulators at the end
> supports of the radial wires. However, a buried radial system is not a
> resonate radial system as a ground-plane antenna, although the radials may
> be at calculated resonate length the effect of ground surrounding the
wires
> changes things a lot. Buried radials' purpose is to provide a low
> resistance return path for the loop current and as such antenna operation
> will not have any notable change if the wires are bare or insulated.
>> However, because of your unique QTH problems covering the wire with a red
> covering seems like a good idea. <g>
>> very 73
> Danny
>
- - -
Your moderator for this list is:
Larry Wilson KE1HZ [email protected]
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