The consensus for placing a 4 element SteppIR and an XM240 five feet
apart is that this is much too close. Although it is true that the
SteppIR can be retuned to lower the SWR because of interaction, you
probably wont be able to recover the loss in gain or F/B.
Thanks to Joe, K4IK for modeling this configuration and modeling some
possible solutions. Modeling shows with 5 ft seperation, on 17 meters
the SteppIR loses 3 dB gain and most of its front to back.
Possible solutions:
1. Turn the antennas 90 degrees to each other
2. Place antennas 5 ft apart and disconnect the feedline (center and
shield) from the XM240 with a relay located at the feed point. (Loses
1dB gain, 6 dB F/B on 17M, and loses 0.5 dB gain, no F/B loss, on 15M)
3. Place antennas 5 ft apart and use an odd multiple of 1/4 wavelength
on 17 meters feedline, to the XM240 and short line when using the
SteppIR. (Loses 1 dB gain, 6dB F/B on 17M, and loses 1 dB gain, no F/B
loss on 15M)
4. Buy a new mast which will allow 10 ft seperation. (Another month
wait for delivery and >$500 expense) This solution in combination with
using the "odd multiple of 1/4 wavelength on 17 meters feedline to the
XM240" loses only about 0.2 dB gain and 0.5 dB F/B, - insignificant.
Thanks to all who replied
Jerry K4SAV
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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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