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[TowerTalk] Antenna Testing

To: "Towertalk Reflector" <>
Subject: [TowerTalk] Antenna Testing
From: "Ward Silver" <>
Reply-to: Ward Silver <>
Date: Wed, 17 Oct 2012 08:10:55 -0500
List-post: <">>
As K9YC and others observe, this is a highly non-trivial exercise and takes 
weeks.  I just do not have the time for the undertaking.  That's actually part 
of why we published the detailed that some other motivated group 
could build on it.  Another possibility is for one of the big antenna or 
aerospace companies to make a test range available for a day or two and have a 
large group do it like Field Day.  But the writeup and data-crunching will 
still take many, many hours.

K5GO's idea has merit - given the availability of sophisticated modeling, much 
of the data could be generated computationally.  However, that presumes 
accurate models that aren't cherry-picked or biased...perhaps third-party 
models could be developed.  But any model would have to be validated...and that 
requires testing.  Furthermore, modeling would not have uncovered the problems 
with the KT34XA trap rebuild kit or pointed out that there might be feed line 
interaction on the PRO-57B.  And neither do you get a feel for whether the 
antenna is a mechanical nightmare or exceptionally robust or came with missing 
or cheap hardware or whatever intangibles that models don't include. So there 
is no free lunch when you get right down to it.

And there are political issues...I remember the neighbors got mighty nervous 
when there were five big antennas assembled on sawhorses  in the north pasture 
:-)  They were greatly relieved to hear that I was only planning a test and 
some of them offered to help - no doubt to speed its completion and get the 
antennas on their way.

More seriously, building up a set of data like Rob Sherwood NC0B has done for 
receivers might be a good long-term project.  Someone would need to make a 
commitment to maintaining a decent test range in a consistent configuration.  A 
standard protocol would have to be developed and the equipment to implement it 
maintained as well.  Over a period of years, a set of data could then be built 
up for comparison.

On the other hand, with antenna modeling so powerful and ubiquitous, claims of 
extraordinary performance ("Flash!  Just worked South America!") are much 
harder to make (more than once) and so the need for third-party checks has been 
reduced.  I applaud companies that take great pains to publish free-space dBd 
values with all the necessary supporting data such as elevation angle.  Don't 
be afraid to ask for that data - if it's not available, take a closer look at 
the claimed performance and the antenna itself.

73, Ward N0AX

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