<<<I have installed di pole antenna for 40,20 and 15 meters in the terrace
of the apartment complex which is on 22nd floor, the coex to my amateur
radio rig( Yaesu FT 847) on 14th floor is abt 35 meters in length.>>>>
Since the noise all comes from one source, you can eliminate it with a noise
canceling device. I would recommend a MFJ-1025. I have measured many units,
and the MFJ is far better than any other unit for this (assuming MFJ builds
it correctly, their quality control is terrible at times).
The noise canceller must be connected to a "noise antenna" very near the
elevator controls. Placing the "noise antenna" closer is much better, but
not closer than 10 or 15 feet!!
Then you can null the noise out of the dipole, and not remove desired
signals. Depending on the exact method of noise radiation to the dipole, you
should get anywhere from a modest 20dB reduction to total elimination.
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