The N4KG system looks good when evaluated for SWR and ease of
installation. It, however, has serious performance issues.
1) W8JI and others are right - there can be significant ground
losses depending on the division of current up/down the
tower from the "feedpoint". The only time that loss is
truly negligible is if the tower is *NOT* grounded (mounted
on insulators) and all feed/control lines have high impedance
chokes at ground level.
2) The division of current up/down the tower can also result in
significant skewing of the take off angle and cancellation
(currents are out of phase due to the ground connection) at
critical angles.
Unfortunately, Cebik's models understated ground effects - particularly
real (lossy) ground.
73,
... Joe, W4TV
On 2019-09-06 12:09 PM, 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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