I actually found a post that N4KG himself made a couple of years after
his QST article where he mentioned that the performance of his inverted
system seemed to be worse than what he once had with a full set of
buried radials under a shunt fed tower. He pointedly stated that the
lower the elevated radials on his inverted system, the worse the
performance even when matched.
As you say, SWR doesn't tell the full story for actual performance.
73,
Dave AB7E
On 9/6/2019 12:55 PM, Joe Subich, W4TV wrote:
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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