On Thu, 01 Aug 2002 <firstname.lastname@example.org> writes:
> I used the ARRL Antenna Manual and found a "window" of lengths
> that matched my purposes... 28 feet seemed to work to avoid
> resonance on the HF bands.
N4KG: WRONG !
28 ft is self resonant at 17.6 MHz (near 17M),
or possibly lower due to end effects of the loops
through the insulators.
Did you remember to put an insulator at the TOP of the
uppermost guy? If not, you have continuity for 57 ft from
the insulator at 28 ft plus 1 ft through the tower plus another
28 ft to the first insulator in each of the other guys.
> That length is reasonably long enough so that you aren't breaking up
> the lengths of the guys "too" much. I
That is a popular THEORY.
I place my first insulator 3 to 5 ft from the tower to keep the
close in lengths (through the tower) well below a half wavelength
at 10M, then use one or (preferably two) 10 to 12 ft lengths for the
same reason. Then I go to 27 or 40 ft lengths. This works well
for antennas mounted at the TOP of the tower. Side mounted
antennas may need more short guy lengths overhead to prevent
When modeling a 2L 6M antenna I noticed an interesting fact:
The parasitic element (spaced 0.15 WL) became invisible ONLY
if it was LESS THAN 0.3 WL long. ANY length over 1/2 WL
acted as a Reflector, providing GAIN and F/B, truncating at
2 dB gain and 4 dB F/B all the way out to several wavelengths.
ANY length over 0.3 Wavelengths WILL couple to nearby antennas
and affect the pattern. The only way to know for sure what
is happening is to model the ENTIRE system, including antennas
and Guy Wires.
t took me about 6 hours of work for a set of three guys
> to break them up. 18 hours total for a 100 ft. tower. The clamps
> and the insulators were a little expensive. But now I know that no
> what HF antenna I might put up in the future - I shouldn't have
> with the guys.
> On Thu, 1 Aug 2002 14:41:30 +0300
> <email@example.com> wrote:
> I guess it also depends on what antennas you have on the tower. If
> just one
> monobander then it would be fairly easy to find nonresonant leghts
> of EHS
> guy wires with modelling. But if tribanders etc.. then they will
> effect some
> band one way or the other.
> That's my conclusion after a lot of modelling. Having tribanders and
> Yagis on the tower I know that I could never sleep peacefully not
> terrible nightmares about those lost db-s if having solid EHS wires.
> breaking them up into smaller lengths than half wl on 10m is making
> project as expensive as Kevlar already and more troublesome...
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