> OK, I'll bite... Why would you put up a 5/8 wave vertical? Have you
> modeled this dog?
Only a nibble, not a bite,
The question had to do with using a 5/8 wave vertical and radials.
In early days of AM radio, and I have spent most of my work life in
Broadcasting Engineering, a 5/8 wavelength vertical was sometimes used.
This because it was close to the maximum vertical length and gain before
much high angle lobe developed.
The reason was to reach the maximum number of listeners via the lowest
angles. However
in the nightime hours it did not function well. Angles were way too low for
normal skip conditions.
So a "big low angle signal" is right. Modeling to see the gain has to be
done at very low angles. 10 to 15 degrees above the ground. However at
these very low angles the Pseudo Brewster angle losses can be very high and
require long radials. (See the ARRL antenna handbook for a Pseudo Brewster
angle expanation). Sone antenna modeling programs may not include these
losses, (or accurately)
I am currently using near 1/2 wavelength vertical elements on 80 meters.
Earlier I lengthened them by 10 feet. After current setting, phasing, and
rematching the feed system, I took a DX long path loss. (I have a almost
daily 75 meter SS schedule with VK6LK) So I went back to the original
configuration and there it will remain.
A 5/8 wavelength antenna is too long even for normal DX on 80 meters. You
can never say never, because every anenna has its day. For one, I could not
wait for a huge 5/8 wavelength on 160 meters to have its day.
Cheers Denny.
73,
Bruce-K1FZ
> Now, I suspect you are talking about an inverted L - as the 5/8 vertical
> is 340 feet... This is an even bigger dog - unless you want the biggest
> signal for local rag chewing, where it is a killer antenna... It also will
> bask the nightcrawlers in welcome warmth all winter long..
>
> OK, to answer the question, yes you would want the radials long enough to
> mask the radiated EMF from the ground directly underneath...
>
> cheers
> denny / k8do
>
>
>
> _______________________________________________
> 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
|