Saturday, June 2, 2012

Simple Antennas for the Amateur Radio Operator--a continuing series

ANOTHER EMERGENCY ANTENNA

There are quite a few birds in my area that often use my antennas as perches or launching platforms for their flights.  Normally, the smaller birds (finches, cardinals, and an occasional native bird like a honey creeper) don't create problems.  However, a sizeable bird such as a pu'eo (Hawaiian Owl) can damage a dipole or even the bird itself.  Such was the case yesterday when some kind of bird bumped into the 450-ohm twin lead feeding my 40-meter inverted vee.  I cut out the damaged section of the feedline and decided to replace it temporarily with about 50 feet of RG-6 I had stored in the "junque" box.  I didn't have the Drake MN-4 ATU handy at the time, since the MN-4 was being cleaned on the workbench (the kitchen table).

So, I borrowed an idea from Dean, KH6B, and rigged up what he called a "James Bond" antenna--named after the famous fictional spy created by Ian Flemming.  All I did was connect the coax to one end of a UHF "T", ran another piece of coax to my Heathkit Dummy Load, and ran some coax to the venerable Swan 100 MX at the operting position.  Results on 40 and 15 meters were good and the rig didn't seem to mind.  I was even able to round up a few contacts on 20 and 10 meters.  The old Swan remained cool and stable with this temporary and inefficient antenna system.  Although I was perhaps losing a good deal of signal due to the mismatch, I still made some contacts.

After experimenting with this antenna arrangement, I reconnected the inverted vee with a new section of 450-ohm twin lead, fed the new feed line to a 4:1 balun, and ran some coax to the newly cleaned Drake MN-4.  Everything was back to normal in short order.

You may find the "James Bond" antenna a useful addition to your emergency kit.  All  you need is a 50-ohm dummy load, some short pieces of coax, and a UHF "T" connector.

Have a good, productive weekend on the air!

Aloha es 73 de KH6JRM--BK29jx15