There must be hundreds of posts on 'optimum heights /
takeoff angles in the Tower Talk archives.
NO SINGLE Height will cover ALL of the angles
supported by the ionosphere. You need BOTH
high (60 to 120 ft) and LOW (35 to 45 ft) antennas.
The Low antenna will fill in the unavoidable NULL(s)
of the higher antenna(s).
During the daytime, Low Antennas are often better
than high antennas to Europe and Africa. Remember
MOST of the DX stations are using low antennas which
put more energy into higher waveangles that are supported
by daytime MUF's.
Based on considerable contest and DX experience from
my own and other multi tower multi antenna stations,
80 to 100 ft SUCKS on 10 and 15M from mid morning
to mid afternoon, sometimes even on 20M, especially
to Africa, even during low sunspot activity. My 40 ft
high TH7 is ALWAYS stronger to Africa (sometimes by
2 S units) than my Telrex 3L20 at 75 ft whenever it check.
Antennas at 80 to 100 ft play well after dark, especially
on 20, 30, and 40M. I like 40 to 60 ft for EU / AFR on
10 and 15M. Higher antennas can be useful to Asia, especially
as the bands open / close and after dark. Surprisingly,
high antennas are sometimes better for South America,
and Central America / Caribbean as the bands close
and low angle single hop is the only mode that is
propagating. This is especially true in W4 in the late
afternoon / early evening on 10 and 15M.
For the high bands, I would recommend 60 to 70 ft for a
high tribander with another smaller (2L or 3L) tribander or
even a triband dipole or two at right angles) side mounted at 40 ft.
120 ft is a nice height for a high tribander since the second
lobes falls in useful high angle ranges. A lower antenna at
40 to 60 ft is still needed to fill in the first Null. (The second
lobes at 80 to 100 ft are too high to be useful, another reason
I don't like those heights for high band antennas).
Tom N4KG (with 20 antennas on 7 towers)
On Wed, 9 Jan 2002 "John Benedict" <firstname.lastname@example.org> writes:
> Hello Group
> I have 100 feet of 45G tower and would like to put up a 36 boom
> Pro-95 multi-band antenna. I would like to find out how high I
> should put
> the antenna in order to get the best performance out of it. Is
> going from
> 80 feet (which would be easier take care of (guys, wind, climbing
> etc...) to
> 100 feet gain anything at all worth while? Is it worth going up to
> 100 feet
> with a antenna that has about 18 square feet of wind load? Are
> there any
> other benefits to going so high?
> Thank you
> John Benedict
> KE5RS in Leander, Texas
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