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[TowerTalk] Antenna Testing

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Subject: [TowerTalk] Antenna Testing
From: (Ward Silver)
Date: Fri, 13 Feb 1998 07:35:23 -0800 (PST)
On Thu, 12 Feb 1998, K4SB wrote:

> Well, this one is going to be with us for awhile. I think we'd all be
> interested in a detailed
> description of the "antenna range" setup:
> 1.Preliminary steps to determine a base reference for 0 db
> 2. Height of the dipole and reference antenna
> 3. Step attenuation device used.
> 4. Equipment used to measure the gain.

As the test designer, I must hurry to state that a complete dicussion of
the results and test protocol is beyond the scope of reflector messages.
There will be a published report that goes into great detail about the
tests, including tutorial material and comparison to models.

That said, let me summarize very quickly.  If you have questions or
comments, I would appreciate your "holding fire" until the report is
actually published when you can more accurately assess the entire test
program, its goals, and its limitations.  The paper will be presented at
both Visalia and Dayton.

1) All gain measurements were taken with respect to a reference full-size
dipole made from aluminum tubing, mounted on the same mast at the same
height, and driven with the same feedline and balun as the antennas
tested.  The tower was a self-supporting HDBX48, with the antennas mounted
at approximately 50' above ground.

2) Received signal strength measurements were made with an HP8550-series
spectrum analyzer in which power was read directly in dBm.  There were no
step attenuators or preamps used.  The same receive equipment, including
cables, were used for all tests.  Spectrum analyzer linearity was checked
against a known attenuator and with a power meter.

3) The receiving antenna was an A-4 at 70' on another self-supporting
tower, approximately one-mile distant, with a clear line of sight over the
harbor between the sites.  The absolute elevation MSL was equal to within
20' over that distance.

4) The goal of the tests was to develop a "reasonable" and repeatable
protocol for comparative testing that could be performed by other hams
without requiring access to extraordinary facilities.  This was not an
attempt to validate manufacturer's gain or pattern specifications.

I hope that gives a little background on the testing without trying to be
exhaustive...this is about as far as I can go without starting to
reproduce the test description out of context.


73, Ward N0AX

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