N4KG response below -
On Wed, 04 Mar 1998 04:24:48 +0000 Tom Rauch >
>> By the way my "vertical" is a tower with raised radials, the radials
>> going to the coax center conductor and the shield to the tower..
>> The N4KG method...... (K9FD)
>
>Not only with Beverages nearby, it also works better for
>transmitting. Raised resonant radials radiate like crazy and couple
>to EVERYTHING else in the near field (including lossy soil below the
>antenna) no matter how much time is wasted pruning and tuning. The
>fields from each radial only cancel completely hundreds of feet away,
>and that is where they don't cause power loss. (W8JI)
>
>You also likely give up a lot of useful RF to the loss in the tower
>to earth connection, which modeling programs often "think" is a zero
>ohm zero loss connection. In the real world, a tower stuck in the
>mud is not a zero ohm lossless earth termination! (W8JI)
>
>Raised radials are a great idea if they are installed a hundred feet
>in the air, but place anything (including good ole dirt) within a
>pretty large distance and the radials couple like crazy to
>whatever the other conductor is. And that's true no matter how
>much time is wasted "tuning and pruning" them for equal currents.
>
>73, Tom W8JI
>w8ji.tom@MCIONE.com
>
...............................................
Hi Tom -
I agree that my elevated GP antennas have losses due to the earth
connection
and low radials, but you make it sound like such antennas are not much
better than a dummy load and on this point I must STRONGLY DISAGREE.
(My GUESS at WORST CASE losses compared to a full size ground based
vertical with lots of radials is 6 dB. My HUNCH is that it is actually
much LESS.)
My 80M elevated GP has accounted for 225 countries since I started
tracking
it's performance. While I do not have direct comparison data, I expect
that
it performs MUCH BETTER than a GAP or heavily loaded multiband vertical
or base loaded vertical.
On 160M, I have recently worked 3DA0, 5A, 5B4, H44, KH9, S7, YB, ZL7,
Antarctica, and many JA's and Europeans with 1000W (QRP on 160!)
feeding a 140 ft tower with 6 elevated radials at 15 ft. Signal reports
and
competive "feel" in the pile-ups lead me to believe that it is comparable
to others in the state using top loaded verticals against ground radials.
I recently installed a full size folded wire vertical (61 ft up, 2 ft
across at top,
1 ft across at 3 ft up) in my woods, over very wet marshy ground, with 32
radials (8 = 75 ft, 24 = 100 ft), fed with 450 ft of half-inch CATV
hardline
and a quarter wave RG58 coaxial transformer.
Comparisons with N4NO, 12 miles SE of me, and K4AB, 10 miles west
of me, both indicated the N4KG elevated GP was 3 to 4 dB stronger than
the ground mounted vertical. This was something of a surprise. Perhaps
the fact that the vertical is near a (low) creek and the GP/tower is on
the
edge of a ridge which gently slopes to the creek (about a 20 ft drop over
300 ft) accounts for the discrepancy when measured by ground wave.
On RECEIVE, there is absolutely ZERO difference detected either by
S-meter or ear (with the AGC OFF) when listening to skip signals.
On transmit, N4AR/8 saw zero difference. More transmit tests need
to be performed.
Bottom line: Elevated GP antennas ARE effective, quick and easy to
install, and VERY INEXPENSIVE. They utilize an existing tower and
therefore PREVENT PARASITIC INTERATION that would exist if a
separate vertical antenna were installed near an existing tower.
(I have experienced parasitic effects on both 80 and 160M when
verticals were installed less than 1/4 wavelength from an existing
tower which happened to be self resonant near the same band .)
The N4KG Reverse-Fed Elevated GP (June 1994 QST) may be the
BEST alternative for 80 and/or 160M for someone with limited
real estate. It also offers quick and easy access to the low bands
by visiting DXpeditioners to existing HF stations in foreign lands.
de Tom N4KG
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