[Antennas] Vertical

2002年9月28日 15:19:04 -0400

hi folks... my 2 cents worth.. i have a gap titan dx... i experimented
with it and found that it works best 10 feet above ground... above 10 feet
does not increase performance, and the techs at gap said basically the
same.. 73 paul w8jn
----- Original Message -----
From: "Jim Shaw" <[email protected]>
To: "Charles Greene" <[email protected]>; "Antennas" <[email protected]>
Sent: Saturday, September 28, 2002 3:01 PM
Subject: RE: [Antennas] Vertical
> 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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