I have had a 4 on a 54 foot boom (actually 57 with a 3 foot tail for
balancing) up for over 7 years. (and Fred, K2TR has a pair of 6's on a 54
(57) which has been up at least 10-15 yrs). The boom is made cheap and
easily with 20 feet of 3 inch irrigation tubing slipped over the ends of a
20 foot piece of 2 1/2 inch aluminum emt (a little less than 3" OD). Just
add a few inches of emt in the boom where you have to clamp down for an
element. It has one set of vertical boom supports and is up 100 feet. We
get a lot of snow in the Albany, NY area, but we don't get very much icing.
We also don't get many hurricanes or tornadoes, but we have seen our share
of 50+ mph storms. It moves horizontally a little in the wind, but it's
like the sappling bending with the wind while the mighty oak falls over.
And yes, it is hard on the ego to say you "only" have a 4 el beam when you
really have a 6 el boom! But it really plays!
-----Original Message-----
From: Stan or Patricia Griffiths <w7ni@easystreet.com>
To: Richard Karlquist <richard@karlquist.com>; Towertalk (E-mail)
<towertalk@contesting.com>
To: <towertalk@contesting.com>
Date: Saturday, August 04, 2001 1:44 PM
Subject: Re: [TowerTalk] Wide spaced Yagis
>
>Richard Karlquist wrote:
>
>> I noticed in Chapter 8 of W2PV's Yagi book, he shows that for a 20 meter
>> Yagi on a 54 foot boom, there is little difference in gain whether you
use
>> 4, 5, or 6 elements. What I don't understand is why you never hear of a
54
>> ft 4 ele Yagi, but 5's and even 6's are commonplace. This is kind of
>> analogous to the question of why people bother with 4 element Yagi's on a
30
>> ft boom when a 3 element on that boom has slightly more gain. I notice
in
>> the ARRL antenna book, there are a bunch of reference designs for Yagis.
>> The 10 meter ones are more widespaced (in wavelengths) than the 20 meter
>> ones. Why? Seems like they should be scale models of each other. Am I
>> missing something here?
>
>Well, I don't think you are missing anything really mysterious here. 54
foot
>booms are hard to make strong enough to stay up through years of rough
>weather. It has been done but it wasn't easy (or cheap). You could
probably
>make a boom 40 feet long for half the cost and with half the weight in
>aluminum. On ten meters, a boom equivalent to a 54 footer on 20 meters is
only
>27 feet long . . . easy and cheap.
>
>Also, I don't think the information in W2PV's book is really widespread
>knowledge among average hams, even those who have monoband Yagis, so it
should
>not be too surprising that is not applied often.
>
>I think the most import point, however, is "bragging rights". It is common
to
>hear someone brag about the number of elements they have but rarely do you
hear
>them bragging about their boom length. Most hams simply "feel better"
about
>owning a 6 element 20 meter beam than they would about owning a 4 element
20
>meter beam regardless of the relative performance of the two. This is just
>"human nature" and has nothing to do with real antenna performance. K6ASL
once
>had a 5 element 20 meter Yagi on a 60 foot boom . . . very impressive. It
was
>up about a year until an irate neighbor cut the guy wires . . .
>
>Stan
>w7ni@easystreet.com
>
>
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>
>-----
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>
>
List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
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supporting towers up to 96 feet for under $1500!! http://www.anwireless.com
-----
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