If you make the combination of the length of the radial(s) plus the
length of the tower above the radial(s) equal to an electrical half
wavelength, everything on the tower below the radial(s) is choked off.
You can easily see this by looking at the current distribution in EZNEC.
So yes, N4KG's approach should work fine, although I don't see how it's
any simpler than using a shunt feed. Both require you to find a
suitable point on the tower, and I'm not sure trimming radials is any
easier than adjusting a capacitor.
It seems to me that the advantage of N4KG's approach would be that wire
is cheaper than a good quality capacitor, and possibly that elevated
radials require less wire than a radial field.
73,
Dave AB7E
On 9/6/2019 9:09 AM, Dave Thompson wrote:
Gang,
This is my annual request that there is a simpler way to feed a tower. Tom
N4KG wrote an excellent article on his reverse feed system in the April 1994
QST. With Tom's system using elevated radials (either loaded or full length)
you feed the coax to a radial and the shield to the tower. We used a MFJ 259
to find a place to attach the radials for a match on the tower. Tom also had
an excellent section of calculating top load to get electrical length. If you
don't have the actual QST you can down load the article.
Cebik contributed an article on reverse feed of towers and showed that there
little ground loss that W8JI and others predicted.
We did two towers one 60 feet and one 90 feet and the results were very good
with great DX. Tom ran several towers and most low band DXers know his
results. Sadly Tom became a SK last year. Best DX was Zone 17 on CW and Zone
25 UA0 from GA on SSB.
73 Dave K4JRB
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