[TowerTalk] Measuring DX Performance of Verticals

Steve Katz stevek at jmr.com
Wed May 7 11:24:16 EDT 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 judge multiple skywave paths simultaneously, this does seem to be an
> issue; however to get a pretty good feel for one or two well known skywave
> paths isn't so difficult.  When I compare antennas, I use nearly
> instantaneous switching (coax switch, local or remote) and "beacon" type
> signals, such as those broadcast 5 days a week by W1AW in the form of
> their code practice and bulletins.  W1AW is almost precisely 3000 miles
> from me, and it's obviously a skywave path, and although there is indeed
> QSB over the path most of the time, taking dozens of readings over a
> period of a few minutes and then averaging those to find the mean signal
> strength (as well as standard deviation, if you wish) isn't a big chore at
> all, and I've done it many times.  If you take a reading every ten seconds
> for five minutes, using two or three antennas in a comparison trial, then
> average all those readings for each antenna, you have a pretty good idea
> which one is working better for that path.  Maybe not for "all" paths, but
> certainly for that one.
> Then, I switch to a different "beacon" type station...10m is full of them,
> 24/7 of course, from many directions...but if 10m isn't open, there are
> beacon-like stations on other bands, including CHU on 7335 kHz, etc.  I
> even use high-end-of-the-radio-dial AM BC stations to compare 160m
> antennas -- pretty close.
> -WB2WIK/6
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