Noise cancellation on 2m using 2 antennas

A while ago, static-type QRM was encountered right across the 2m band.

It proved to be a nuisance while receiving weak signals using either of the shack antennas - a 1/4λ Ground Plane at a height of 15m and a Slim Jim at a height of 10m, located 5m apart.

The noise was presumed to be of commercial origin as it was not present at nights and on weekends.

Then, on an impulse, both the antennas were connected to the rig through a BNC-T connector. Surprisingly, the QRM disappeared and the audio level went up considerably.

The offending noise had been phased out just like that!

The antenna feeder lengths were then changed one at a time. The QRM promptly returned, confirming that it was indeed phase cancellation at work.

SWR was 3:1 with both the antennas connected. Inspite of that, it was now possible to comfortably work through a distant repeater.
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PVC-encased Vertical Antennas for 2m

These PVC-encased 2m vertical antennas were built years ago.

PVC-encased TV Ribbon J-Pole & Slim Jim Antennas

One is a J-Pole, housed in a thick-walled  ¾” PVC pipe, with a SO-239 connector. The other is a Slim Jim, in a thin-walled PVC pipe, with a BNC.

Both were homebrewed, using 300 Ω TV Ribbon, with good results (SWR < 1.5:1). The ends were sealed against water ingress using 'M-Seal' (epoxy sealant in dual component lump form).  

     

TV Ribbon

Thanks are due to W0IPL - OM Pat & N4UWJ - OM Don, for construction details of the J-Pole & Slim Jim respectively.

Related post: Sleeve Dipole Antenna for 2m

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