Friday, November 28, 2008

Rockmite 20: Dipoles Really are Bi-Directional

I was back up on Sourdough Trail with the Rockmite 20 on Wednesday. The weather was gorgeous and as long as the sun was out it was warm enough to shed a few layers. I ran into a few dove as I hiked up out to the end of the ridge, but the resident moose must have been hiding out.

I hung the dipole between two trees at the point of a ridge line that points off to the East at an altitude of 10,200 feet. The antenna was oriented just a little bit to the northeast due to the positioning and availability of suitable trees for antenna supports.

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KD0FNR station location and antenna orientation
Antenna support

After CQing for awhile, I was rewarded with a callback from KB8AP in Central Point, OR who provided me with an RST report of 439 while I could read him at 239, RST reports being rather subjective things with the Rockmite since it has no S meter. After we chatted for a bit, I CQ'ed again and immediately heard back from KC8ITC in the opposite direction, Saline, Michigan with a report of 559! Sure enough, just like the very nice write-up on on dipole antennas at Wikipedia predicted, I had a nice bi-directional radiation pattern. This little radio is a constant source of entertainment. It's a great excuse to go wandering around in the forest, and it consistently provides greater than 1000 mile per watt QSOs!

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These great contacts on the dipole got me to wondering what could be accomplished with a Yagi antenna. The Yagi provides directionality and gain by pushing more RF energy in a single direction. Next week I'll try it out. The guys at the Rockmite Yahoo Group have been helping me with antenna design tips. They have already provided one good pointer in suggesting that I not let the dipole actually come into contact with the trees I'm using for supports. The higher the dipole and the more isolated it is, the better its radiation pattern should be. They're providing lots of good ideas for tuning Yagis to the 50 ohm Rockmite as well. They pointed out the BLT QRP antenna tuner[pdf] and that led to the N7VE LED SWR bridge[pdf]. I'll keep you posted if I try them out.

Have fun!
73 de KD0FNR

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