Hi Ron, I have played and fooled around with verticals for many years and as
my friend K3RA, Rol Anders says... "A vertical radiates poorly in all
directions!!" LOL! At present I do have a vertical dipole... Gap Challenger
Vertical and it does perform acceptably! But, I also have a dipole up about
35 feet up.
I think it was the HyGain 14AVQ or the 18AVQ up on the house roof with
radials/guide wires for all bands and had it all grounded to a 1/2 pipe that
ran down along outside of the water well for 200 feet. Now maybe that setup
was not suppose to work but it worked like gang busters. At sundown when the
bands started going out the beams lost it but I stayed right in there with
the DX! That was many years ago when I lived in Tenn. at the Sequachie
Valley. Our Parsonage was up on a hill and I was in the clear. That was in
the mid 60s. I have tried some unique grounding devices through the years
and they worked out pretty good.
Mercy, I even tried the old Gotham vertical from Miami Beach... The 23 foot
vertical I was using a Gonset G66B Receiver and a Elmac AF 67 Transmitter in
Cedartown, Georgia. I was not sure I was getting RF to the vertical so I put
the transmitter in Key Down and went outside and touched the vertical with
the palm of my hand.... It took weeks for the burn to heal on my hand. I was
a novice then and knew very little. My radio teacher who was preparing me
for the General class license took pity on me and built me a 75/40 dipole
with one coax. I had the 40 running east and west and the 75 running north
and south. Come to think of it It must have been a NVIS antenna!! <g>
I had a Gap Eagle Vertical back in 1993 and it performed well with the
ground plane it uses. Had it up a few feet above the roof.
I have some information I want to share about NVIS antennas but will leave
that for another email.
Paul
Paul Gates
K1 #0231
KX1 #1186
XG1
[EMAIL PROTECTED]
----- Original Message -----
From: "Ron D'Eau Claire" <[EMAIL PROTECTED]>
To: <elecraft@mailman.qth.net>
Sent: Friday, August 12, 2005 12:44 PM
Subject: RE: [Elecraft] RE: Low Antenna on Mountain Top
Bill, W4ZV wrote:
Over flat terrain, a dipole up ~1/2 wavelength
has 7-8 dB gain over a vertical at typical 30
degree takeoff angles. On a mountain top, the TOA
goes down because the effective height is raised.
---------------------------------------------------
When people say "vertical", they usually mean a 1/4 wavelength (or less)
radiator. Such verticals are HUGELY dependent upon the ground return for
their efficiency. There's been an on-going argument about that since Marconi
hisself was tinkering with them, but that standard for comparison is that a
1/4 wave radiator should have something on the order of 50 to 100 0.2 wave
radials if it's going to be comparable of a 1/2 wave radiator. That's not to
say an vertical is always inefficient, but that one can't really assess how
efficient it is when using other ground systems and locations. The only
exception to that is a vertical over salt water, as in at sea on a ship.
Short of such a massive ground system, a decent comparison with a horizontal
1/2 wave radiator can only be made with a vertical 1/2 wave radiator (or at
least with radiators of the same physical length if both are less than 1/2
wave).
Even then there will be huge differences based on the propagation involved,
although on HF it's far less than VHF and above. On HF,
reflection/refraction of the wave in the ionosphere pretty well rotates and
mixes the polarization.
Ron AC7AC
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