W/resp to antenna pattern measurement techniques, some very important things
been posted here, in fragmented form, from several knowledgeable guys:
* You can measure at 0 degrees azimuth, using a friend a few miles away, on
* Use the telephone (or 2 meters) as a backchannel for coordination &
* Vary the TX power, holding S meter reading constant. Use a real
Take data at fixed rotational intervals.
* If possible, disable the AGC and digitize the audio in your soundcard,
varying TX power. (The latter, of course, seems to lack a software
* Recognize that the pattern at 0 Az. isn't the same as at real arrival
The data will be useful for comparing antennas against each other, or
but NOT as an absolute. It will be affected by terrain and structures.
be adequate to determine 'reasonably correct' function, decoupling of
adjacent antennas, etc. I have found that it validated specifications
T8, 3 el SteppIR, and multiple kt34A and XA's. And, of course,
the 6dB f/b
ratio on my vertical, which was coupled to the lpda via common-mode
on the feedline.
As an aside, there's a program called "S-Meter", which takes meter readings
via the radio
interface, for those rigs which report S meter data. While this leaves you
measurement error due to the AGC response curve, it should produce a
visualization of the
pattern. My sense is, most S meters tighten up above S9, and may expand
below S3 or so,
and it will tend to understate gain and f/b, and overstate the depth of
The LPL technique, of holding S meter constant and varying TX power, will
So would turning off the AGC and digitizing the audio.
If anyone finds a program to support the latter, I'd like to know about it.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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