My greatest success on 80m has been using a 60' Universal tower,
insulated from the ground with fiberglass rods, and a radial system
composed of 100 radials .. 60 equally spaced at 6 degrees each .. with
the remaining 40 radials placed at one-degree intervals in the four
directions of primary interest ... NE for Europe/Middle East .. W for
VK/ZL .. NNW for JA/BY .. and SE for Caribbean/etc.
The south pasture was mowed TO THE GROUND, and the radials were then put
in place, the insulation at the ends of the radials PULLED beyond the
wire ends to insulate them from the soil, and all radials held in place
by small wire 'staples' made of 1/8" aluminum wire, which eventually
oxidized and disappeared ... just as the grass grew to cover all the
radials.
Don
N8DE
Tom Rauch wrote:
>
> > The biggest advantage of a buried dense radial system over an elevated
> > one, is that it's buried and you can grow grass on top of it. Up in
> > the air gets ice, falls down, and you can see it, etc, etc.
>
> Other problems are with small elevated systems, even at great
> height, you need to choke RF off the OUTSIDE of the feedline or
> efficiency suffers.
>
> You can NOT have a path to earth for RF, and that means you
> can't have a direct connection to earth for lightning. Not a good idea.
>
> Also, no matter how well you "balance" currents, the radials will
> radiate quite strongly in the area around the radials. That means
> interaction and unwanted coupling.
>
> Small resonant systems are also single band systems, and they
> even narrow the antenna bandwidth on the desired band!
>
> All the above, even if we ignore the reduction in efficiency and
> mess of wire in the air, is enough that I won't use them!
>
> > In the ground screen you suggest, you need to pay attention to
> > "dense". Depending on who you talk to, dense starts somewhere between
> > 60 and 120 radials.
>
> RCA spent a fortune on studying this, and they concluded 50-60
> 1/4 wl radials acted like a solid plate. The key is to not let the open
> spaces exceed about .025 wl between wires. That even works with
> a screen reflector antenna!
>
> The 120 radial wires comes from the FCC's recommended ground
> of 120 1/2 wl radials for BC stations, where they want a LOT of
> headroom on the conservative side.
>
> 73, Tom W8JI
> W8JI@contesting.com
>
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List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
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