On 5/29/18 10:06 AM, Ed Sawyer wrote:
I have 2 towers separated by 140 ft. Monobanders. The towers are running
roughly N/S so I am not fully pointing at one when beaming EU but its not
"tip to tip" either.
Keeping this "antenna" related - 140 ft is 2 wavelengths on 20m. On the
lower bands, you're substantially less than wavelength apart, so the
interaction is probably predominantly "near field" - that might make the
pointing direction irrelevant. The distribution and direction of the
electric and magnetic fields (esp if there's significant directive gain)
may be substantially different from what's in the far field.
Tip to tip, 90 degrees, or some other configuration might be the "worst
case".
Are your monobanders 3 elements, or more elements? More elements
implies more stored energy (larger amplitudes) in the near field.
Some of the newer rigs, using many stages of pre-amps on an SDR seem to be
more susceptible for this than others.
Probably depends on the front end selectivity - a lot of SDRs run a sort
of "wide open" front end, and get their ultimate selectivity in
software. Which doesn't help if you're getting IMD in the front end or ADC.
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