[Top] [All Lists]

[Towertalk] Log Periodics

To: <>
Subject: [Towertalk] Log Periodics
From: (Jim Henderson)
Date: Tue, 02 Jul 2002 02:18:48 +0100

    Here is my dos centavos worth.

    Amid much derision and laughter locally, I put up a KLM 7-10-30 8-el LP at
my White Sands, New Mexico QTH back in 1986. It was on a 73' 25G guyed for the
110 MPH zone; it was not only the tallest thing for miles around, it was about
the only tall thing. Took much care to ground everything well, even running
wires from the tower/guy grounds to the metal fence around the 2.5 acres.

    My neighbor, good friend, and QSL manager for many of my old overseas calls
(K7UP) was 1/2 mile down the road, with a 4el KLM 40 at 85', Hy-Gain Long Johns
at 65-80 for 10/15/20.

    Over the course of 4 years of neighborly DX hunt & pounce DXing with the
same power out (L4Bs at 1000W), we amassed a lot of anecdotal info, and made a
point of comparing our signals with seasoned ops at the other end.

    About %75 of the time, on any particular opening on any band, I could open
and close the band compared to his Long John at the same height. I would hear a
given DX station earlier and later  in the opening compared to the K7UP and his
Long Johns. This would get me in the log sooner most of the time, and let me
chase something else while he was waiting for the band to peak on his antennas.
All the local joking began to cease under the weight of the evidence of my
success with the LP.

    When the band peaked for that particular station, K7UP and his Long Johns
would get a better report (say 59 to my 57 or 58 on SSB, and about the same on
CW) about %75 of the time. Once in awhile, the situation would be reversed.

    While the KLM LP had less gain "real" gain, it had gain on a very broad
vertical beamwidth, while the stacked LJs had narrower beamwidths. Hence
whatever the incoming wave angle or required TOA, there was always at least a
little gain with the LP; whereas it appears with the yagis there were enough
holes between the lobes that the contact at that moment was lost, at least until
the conditions changed.

    On 40m where he had a 4 el to my 1 element, the LP was rarely able to
outperform his KLM.

    BTW, this antenna survived a freak January wind storm one year, with
sustained gusts reliably measured at 114 MPH peak, and average winds over 65 for
8 of a 12 hour  period. This wind brought down the County commercially inatalled
Sheriff and medical services tower, as well as several ham towers and antennas
in the region. Not even a piece of this well made LP so much as came loose.

    And after 14 years continuous service in the  high UV and constant vibration
low winds of the
southern New Mexico deserts, it was retired with honors when I moved to Arizona
in 1997.

    I should add in response to recent insulated guy comments, I had my towers
guyed with 9 wires, none insulated. In fact I had several 1/4 wave slopers made
from 450-ohm line hanging off the tower bisecting the guys, and while I am sure
this could have been vastly improved, I worked a lot of DX on the low bands with
these. And when I took the LP down, there was no evidence of ANY lightening
damage, even though there were no less that a dozen times I saw lightening hit
within 2 or 3 blocks ot this structure in the 14 years I had it up.

    Mike and the KLM guys built one great antenna with that 7-10-30, and I am
sorely missing the like of it here in Arizona. I doubt I could get away with
putting the current M2 version of that up here, even if I could afford it. But I
can always dream a little.


Jim, KF7E
ex 5X1XX, 7Q7JH, A35JH
KF7E/A3, /Z2, /V51
et al, etc, etc

PS I have all the logs now...:-)


<Prev in Thread] Current Thread [Next in Thread>