2m-window-loop

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Revision as of 20:43, 25 December 2011 by N8vi (Talk | contribs)

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The e-room 2-meter window antenna

I3-window-loop.jpg
We have forever had a 2-meter/440 amateur radio rig in the e-room, but no antenna. I decided to fix this with some of the copper foil tape I'd recently found use for prototyping SMD boards.

The antenna is a full-wave 2-meter loop, made of copper foil tape, and attached to the e-room window. With a little bit of trimming, I was able to get a 1.2:1 match across the whole 2-meter band.

The antenna is matched with a half wavelength of coax. This takes the unbalanced signal coming in from the transmitter and sends half of it straight into one side of the balanced antenna, while delaying the other half of the signal 1/2 wavelength and feeding it into the other side of the balanced antenna 180 degrees out of phase.

The antenna appears to work fairly well on 2-meters, despite being not terribly high up. More testing is required though.

Theoretically, the antenna should work on 70cm/440, as resonant antennas usually resonate at their intended frequency and all of its odd harmonics. I have been unfortunately unable to verify this empirically, as my antenna analyzer appears to have given up the ghost.

N8vi-window-loop.jpg

Originally, I tried this on the inside of the window of my van, as my employer had elected to move our company to a new building where the only place you can park has very low ceilings, and this seemed like the only solution (besides putting up and taking down an antenna daily).  It seemed to work out pretty well, so I figured I'd try it again.