Here is how the testing is described on the SteppIR site...
(http://www.steppir.com/, click the Field Test button)
----
"We started by placing a reference dipole at one end of an antenna
range and a receiving dipole at the other, with both antennas being of
an equal height of 48'. From the reference dipole station a 100 watt
CW signal was transmitted via an Icom 706 transceiver to the receiving
dipole, with the signal strength characteristics being recorded by an
HP 141-T spectrum analyzer. This was done for each frequency to be
tested. SWR measurement was accomplished with a Bird model 4391 RF
Power Analyst. The reference dipole was then replaced with the SteppIR
Yagi test antenna. The two antennas were on level terrain, separated
by a distance of 705 feet. A CW signal was transmitted from our
SteppIR Yagi, beamed directly at the receiving dipole, with the HP
141-T acting as the "receiver". The differential between the recorded
gain of the reference dipole and that of the SteppIR Yagi (in the
exact same conditions) determined our actual forward gain at a given
frequency. We also performed front to rear tests. Front to rear is the
response from the back of the antenna at it's least favorable point.
Front to back, on the other hand, is simply the response of the
antenna at exactly 180 degrees. In many cases this is not the worst
case response from the back of the antenna. We feel that specifying
front to rear measurement is much more useful to our customers. Also,
keep in mind that front to back varies with the angle of arrival of
the particular offending signal."
-----
Similar to the technique used by N0AX and K7LXC for the triband beam
comparisons detailed in their book "HF Tribander Performance, Test
Methods & Results, 2nd Edition".
73
Patrick
W7TMT
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Tom Rauch
Sent: Wednesday, March 16, 2005 11:08 AM
To: jimjarvis@ieee.org; towertalk@contesting.com
Subject: Re: [TowerTalk] steppIR Gain--test method
> If I recall correctly, Mike and Jim have their own range, with the
> unit under test on one tower, and an HP spectrum analyser connected
to
> a dipole on another tower, many wavelengths distant. Tower heights
> were on the order of 60'. A calibrated attenuator was used with the
> SA.
Well, the many wavelengths distant is already a problem.
Measurements would be much more accurate just out of the near field. I
don't know why anyone would measure an antenna in the null of the
pattern, and when a horizontal HF antenna is at 60ft and the path is
long there is a null along the horizon! Bad measurement protocol.
Measurements would also be more accurate with a directional antenna at
the receiver also, and a good meter instead of a spectrum analyzer.
Measurements like this are always a problem. Look at the silly claims
of the RAIbeam and that little two element hex quad thingy. It's
commonplace that measurements made in test ranges that aren't really
test ranges are a few dB off.
> Theoretically, the steppIR could be a bit better than a canonical
> yagi...in practice, it's hard to tell, because the differences are
too
> small to matter.
Bingo....and probably too small to measure accurately also.
73 Tom
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