On 4/23/07, Fred Mott <fredmottcpa@earthlink.net> wrote:
> I am planning to install a large loop antenna for 160/80/40 meters on my
> 155' Rohn 45G tower. I have been reading all the articles and information
> that I have seen. I plan on using ½ inch vinyl coated hardline rather than
> wire. I have read all I could find on electrostatically shielded loops. I
> seem to think that the hardline would work with its outer aluminum conductor
> being the shield and the inter-conductor copper wire as the loop. The
> shield would be open at the top of the tower. The loop would be close to a
> diamond shape in a vertical plane perpendicular to the earth. I would
> assume that the velocity factor of the hardline .81 would change the formula
> from 1005/f to 814/f. The hardline from the loop will intersect the tower
> at approximately 10 to 15 feet and would go straight down through a PVC tube
> into the basement of my Orchard Storage Building. At that point the coax
> shields would be bonded together to a bus bar that connects to the tower's
> grounding system and the inter conductors would connect to a Ten Tec 253
> antenna tuner.
>
>
>
> I would like to hear from anyone that has had any experience with the
> Electrostatically Shielded Loop Antenna. What do you think? Fred Mott,
> AB8AH
Hi,
Well I've used Electrostatically Shielded loops in the past but they
have always been for Receive only. and much smaller than a
wavelength. If you are considering using this antenna for multiband
transmit antenna.. It will not be as good as a Horizontal loop would
be.. Vertical loop begin to exhibit High angle radiation on frequency
above the fundamental 1wave frequency so the radiation angle will be
high on 80 and 40 Meters. Where as the Horizontal loop will exhibit
lowering radiation angles as you go from 160 to 80 to 40M.
If you using this for transmit there is little use in using it as a
sheild loop. If it is for RX only they a loop much less than a
wavelength would work better.
73 Dave
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