Posted by
Jack Smith-6 on
Aug 29, 2010; 6:50pm
URL: http://elecraft.85.s1.nabble.com/Need-K3-dB-Measurements-on-new-160M-Antenna-tp5468244p5475604.html
In evaluating diversity gain of a Z1501D active antenna against
various transmitting antennas, I use two spectrum analyzers, one
connected to the two antennas to be evaluated. The spectrum analyzers
are set for 0 Hz span and a 100 second sweep, providing a signal
strength data point every 100 ms.
Under software control over the IEEE-488 bus, both spectrum analyzers
start sweeps at a synchronized time. The signal strength data from each
is saved to the controlling computer hard drive. The sweeps are repeated
and data collected for a reasonable time, usually 24 hours per frequency.
The data is then post processed to derive useful statistics, such as the
probability that antenna A provides a stronger signal than antenna B as
a percentage of time, in the form of signals from "Antenna A are X dB
stronger (or weaker) than Antenna B Z percent of the time."
Of course, other interesting things can be observed from the data, such
as fading statistics - is it Rician or Rayleigh fading, for example.
Writing this up is on my list of things to get to, but there are many
things ahead of it in the list.
A short answer is that in fact even modest separation (100 feet or less)
between the broadband active antenna and a wire antenna can provide
useful diversity gain even at 7 MHz and some gain at 3.6 MHz.
Jack K8ZOA
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