[Antennas] Vertical

Sat, 28 Sep 2002 12:01:29 -0700

Timely topic as I just was weighing the pros and cons of a new.

1-looks like you found true value in your beach front location!  Might want
to read
"Antennas Here are Some Verticals on the Beach....." by N6BV ("The ARRL
Antenna compendium #6", pg 216).  You have salt water reflections so that is
likely a positive.  Wish I had the same ability!  Not sure if your other
antennas also benefit from that.

2-Elevating a vertical, any vertical, even just a little bit, usually pays
dividends as well.  See "Elevated Vertical Antenna Systems: Is your vertical
system performance up to snuff?  If not, maybe it needs a lift - in
elevation above ground that is!". (ARRL "Vertical Antenna Classics, KB8I, pg
108).  Your homebrew vertical has the radials elevated above ground so that
is, IMHO, a positive as well.

Over the last several months I used MINNEC 3 to model many different
possible vertical configurations for my QTH.  Nice thing about modeling is
that you can change the height by just inputting a single number of how high
above ground you want the antenna.  In every case, elevating the vertical
and radials above ground, even just a foot, improved performance as
predicted by the model.  At 1 WL above ground, the verticals appear to be a
real competitor to the dipole at the same height.

Yes, some commercial verticals are made for elevated mounting.  However,
back in the 70s, I had a 5BTV (a vertical made for so-called 'ground
mounting') that I tried mounting in many different ways (ground w/lots of
radials, roof w/4 radials, etc.).  My conclusion way back then (from
admittedly limited tests) was that any vertical performed better if
elevated.  Nice to have modeling software these days as the tests are much
easier to run with it.  Same conclusion though.  Higher the better!

73 de Jim WA6PX
[email protected]

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Charles Greene
Sent: Saturday, September 28, 2002 10:54 AM
To: Antennas
Subject: [Antennas] Vertical

Hi,

I made up a 20 meter vertical for portable use and installed it on my sea
wall for test.  It is full size, and I used some junk 1" Alunimum tubing I
had in my attic.  It has two radials elevated 1' above the ground.  I made
the radiator slightly short and the radials about 2' long to bring up the
feed impedance to 50 ohms and also the impedance of the radials so one of
them does not hog the current which it is inclined to do if all radials are
at zero ohms.  The first contact I made was day before yesterday, and I got
a S9+20 report from the Fiji islands, running 30 watts on PSK31.  Then I
ran some tests on it. It is loacted about 50' farther away from the house
than my 6BTV and G5RV.  Using Spectrogram, I determined the noise ground
floor was 10 db (voltage) lower than the 6BTV and 16 DB lower than the
G5RV.  The received signals were about the same as the other two, with a
slight edge, 1 to 2 Db stronger.  On comparitive reports I have received on
transmit, it is running "slightly" to 1 S unit more than the other two.  On
DX, it is at the edge and 8' above sea level at high tide of Narragansett
Bay, 4 miles wide at this point.  On the other two antenna, my 6BTV has 22
radials of 480' of wire, and the G5RV is 30 ft high.  Both seem to work
well.  I knew the G5 was noiser than the 6BTV, but that usually does not
come into play unless the signals are so weak they are in the noise level.

I really can't explain why the vertical is so low noise (my house isn't
that noisy), and I would have guessed it would have performed a little less
well than the fixed antenna with a fair number of radials.  I can
understand why it is better on the long haul stuff, as it has nothing
between it and the frezonal zone a mile of two away.  I would appreciate
any comments.

73, Chas, W1CG
K2 #462

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