There is a great deal of positive anecdotal evidence for a vertical
over an impenetrable ground shield. This would include corrugated
metal roofing, copper or metal roofs, chicken wire for as long as it
may last at a given site, etc. My own experience includes a 40
through 10 multiband vertical with two resonating radials per band,
but over a surrounding expanse of flat, copper row house apartment
roofs in Washington, DC. It was my first antenna after college and it
worked gangbusters. In the year and a half I was there, I almost
worked 100 countries on 40 with 35 watts (Knight-Kit VFO and 807
transmitter). If I heard it, I worked it. Hearing and time on the
radio were the controlling factors.
That success was followed by its transplant to a dirt and grass
backyard in suburban Mt. Vernon, Va., with the same radials and a
supporting iron pipe, and its transformation into a dummy load.
At what point do ground radials become impenetrable to RF like the
corrugated sheet metal? Or do they ever?
73, Guy.
On Tue, Dec 8, 2009 at 5:25 AM, <cris@gm4fam.plus.com> wrote:
> If you don't mind the unsightly effect then I recommend as many as
> possible corrugated sheets around the base of the vertical. I use them
> over a full set of 120 x .41 lambda radials on 40m - they make a big
> difference.
> They also stop the rabbits from biting thru the radial wires - in
> September I noticed that a family of a rare species of toad had nested
> under one of the sheets (now marked with a white cross to remind me not to
> tread on it!).
>
> 73 Cris
> GM4FAM
>
>> Yes, when I had inquired on the Towertalk reflector several months ago
>> regarding the use of chicken wire, someone responded privately and said
>> that BC stations had abandoned wire mesh screens many years ago because
>> of undesirable eddy currents. The eddy currents were thought to oppose
>> the return currents and actually made the system less efficient. The
>> writer referenced two engineering books from th 50s, and I suspect the
>> book you mention was one of them.
>>
>> 73, Joe
>> K2XX
>>
>> Thomas F. Giella NZ4O wrote:
>>> BTW I have a 574 page e-book published in 1952 called Radio Antenna
>>> Engineering. It covers LF/MF and HF antennas. I downloaded it for free
>>> at
>>> http://www.lulu.com/content/159004. It says that putting down chicken
>>> wire
>>> type mesh under the vertical is not good due to some sort of RF
>>> cancellation.
>>>
>>> 73 & GUD DX,
>>> Thomas F. Giella, NZ4O
>>> Lakeland, FL, USA
>>> nz4o@arrl.net
>>>
>>>
>>>
>> _______________________________________________
>> 160 meters is a serious band, it should be treated with respect. - TF4M
>>
>
>
> _______________________________________________
> 160 meters is a serious band, it should be treated with respect. - TF4M
>
_______________________________________________
160 meters is a serious band, it should be treated with respect. - TF4M
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