[Towertalk] Log Periodics

[n4kg@juno.com]

Jim,

>From your comments below, it would appear that your LP 'opened 
and closed' the band compared with your friend using the HyGain
5L Monobanders, suggesting you had more signal at the LOWER
angles while his signal peaked during the middle of the opening
and was stronger, suggesting his antennas had more gain at higher
angles.

Yes, a (short) LP has a very broad pattern in the vertical plane,
probably on the order of +/- 50+ degrees relative to the horizon 
in free space at the -3 dB points. A wide vertical pattern is
useful when the MUF is high and the bands are wide open,
i.e. when the ionosphere supports Higher angles (but your
observations reported LESS signal during those times).

The HyGain 5L Monobanders exhibit a vertical beamwidth on
the order of +/- 30+ degrees relative to the horizon in free space
at the -3 dB points which should cover most of the angles needed
for DX, especially on 10 and 15M during the day.

I suggest that the differences you observed were related more
to differences in TERRAIN in your respective foregrounds and
Effective Antenna Heights than any differences between the
antennas.  In other words, your LP was effectively higher 
than your friends monobanders, giving you the edge as
the bands first opened (LOW Angles) but giving him the
edge when the supported angles were HIGHER.

As far as pattern nulls in the Vertical Plane are concerned,
they are formed by the Vector Sum of the Incident and
(ground) reflected waves which are *solely* dependent on
the effective height of horizontally polarized antennas and
have absolutely NOTHING to do with antenna type.

Your observations DO support my contention that 
NO  SINGLE  ANTENNA (or Height) will cover ALL
the angles that are supported by the Ionosphere,

and it's corollary that :
"You can never have enough antennas".

Tom  N4KG



On Tue, 02 Jul 2002  Jim Henderson <jhenders@swlink.net> writes:
> Reflectees:
> 
>     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. 
> 
>     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.
> 
> 73
> 
> Jim, KF7E
> ex 5X1XX, 7Q7JH, A35JH
> KF7E/A3, /Z2, /V51
> et al, etc, etc
> 
> PS I have all the logs now...:-)
> 
> --
> jhenders@swlink.net
> 
> 

________________________________________________________________
GET INTERNET ACCESS FROM JUNO!
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today!  For your FREE software, visit:
http://dl.www.juno.com/get/web/.