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[TowerTalk] Re: K7LXC, et al Tribander Comparison Tests--Questions

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Subject: [TowerTalk] Re: K7LXC, et al Tribander Comparison Tests--Questions
From: K7LXC@aol.com (K7LXC)
Date: Tue, 26 May 1998 19:45:52 EDT
In a message dated 98-05-26 18:45:56 EDT, jreid@aloha.net writes:

<< However,  a great friend, Larry, KM6IU, also heard the talk
 and is still wondering what to do with his big Pro 67 which covers 40 up to
10
 meters,  and with which he has 315 countries confirmed since 1993 when he
 put it up in the hills at his LosAltos, CA QTH;  he also worked the 3B7 on 
 40 meter SSB with it just before leaving for Dayton!!?  

        I never said that the antennas didn't work or radiate. Our tests just
showed that they 'underpreformed' similar sized antennas. 

     Your friend has a location "in the hills at his Los Altos QTH". Perhaps
location is more important than the specific antenna installed. He probably
would have had similar success with ANY antenna at that location. 
 
>> Steve stated that his test range antennas were about a mile separated,
 on 55 foot towers,  and at the "same height,  within 35 feet or so",
whatever
 that exactly means.  In any case,  a yagi on 20 meters is going to have its
 maximum  radiation lobe,  the first one formed at something like a 30
 degree launch angle,  and that I presume is the lobe in mind when
 talking about an antenna's gain,  isn't it?
 
      Well, sort of. If you model the aforementioned yagi at 40, 50 and 60
feet like we did, you'll see that the influence of height isn't as dramatic as
you imply on forward gain. F/B is more influenced.

     Also, the main lobe takeoff angle is a function of antenna height. It's
only 30 degrees at one height.

     Before I go any further - what was presented at Dayton and Visalia was a
SUMMARY of our study. You haven't seen or read all of the information that
will be included in the report. So far we have about 50 pages of protocol,
rationale, data, results, etc. We address ALL of your concerns, some of which
are valid. And you neglected to mention that our biggest caveat during the
presentations (and the report) was that this was ONE test at ONE height at ONE
location. 
 
     <a bunch snipped>
 
>> Also,  Steve's data for 20,  15,  and 10 meter bands,  are all with the
 antenna 
 physical heights unchanged.  How can they possibly represent the way the
 tested antennas actually perform at DX distances;  there is a 2:1 difference
 in wavelength height between the 20 and 10 meter tests as reported!  That
 certainly impacts the radiation angle for the two bands with fixed antenna
 heights.
 
     This WAS NOT a test over DX distances. Get a copy of the report when it
becomes available and read it. THEN you can make more helpful criticisms of
our test. 
 
      What this is is a REASONABLE test with REPEATABLE results REFERENCED to
a dipole. Yes, it's not perfect - we never said that it was. If you don't
believe our results, we hope that you and other people will take us up on our
challenge to conduct your own tests using our protocol to further contribute
to this fascinating topic. But please don't make broad statements regarding
the study without understanding how we got there.

Cheers,  Steve  K7LXC

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