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[TowerTalk] Measuring DX Performance of Verticals

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Subject: [TowerTalk] Measuring DX Performance of Verticals
From: (Jim Lux)
Date: Wed May 7 14:58:26 2003

>The bottom line is that trying to make any kind of an A/B comparison over a
>sky-wave path is pretty much an exercise in futility.  Signal levels swing
>wildly +/-20 dB in a matter of seconds, so comparisons would have to be made
>on a second-to-second basis..  You would need synchronized antenna switching
>systems and some fairly sophisticated test gear to acquire the data and
>separate it into the individual signals.  This is out-of-scope for amateur
>tests and unlikely to provide any real meaningful data.  I have no reason at
>this point to question correlation between the range tests and performance
>over a low-angle sky-wave path.  Introducing the sky-wave path would also
>introduce so many uncontrolled variables that any conclusions would be of
>questionable validity. These are all code words for, "We are not going to do
>sky-wave tests."

One could probably approach this statistically using something like the 
NCDXF beacons.  Log beacon strengths 5 minutes on antenna A, then 5 minutes 
on antenna B, etc, for a suitably long test period (>24 hrs).  Yes, you'd 
need to rig up some sort of electrical antenna switch, but that doesn't 
strike me as particularly complex (one bit from a printer port).  A program 
like BeaconSEE can log the signals quite nicely, and, once synchronized to 
UT, will separate out the various beacons.

Another approach is to use more than one receiver simultaneously.. 
Something like the Icom PCR1000, while not as wonderful a receiver as you 
might have in your contesting rig, does have a reasonably well calibrated 
signal strength indication, and is completely controllable over an RS232 port.

The real point is that you don't need sophisticated test gear... what you 
need is sophisticated measurement design.

Jim, W6RMK

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