Thursday, December 15, 2011

Simple Antennas for the Hawaii Island amateur operator, a continuing series


Today is Thursday, 15 December 2011, the last day of school for the 2011 academic year.  Most of Hawaii's public and private schools will be taking a winter break until 04 January 2012.  For my xyl and myself, the intersession will give us a break from out substitute teaching assignments at Laupahoehoe High and Elementary School.  During the two months I've served as a substitute teacher, I'm not sure who taught who.  Both the students and I have learned a lot about each other.  I don't regret leaving the commercial broadcast business for the classroom.  At least I don't have to get up at 0230 W and drive 30 miles to Hilo and sit before an audio board and a computer for 14 hours a day, six days a week.  My radio experience was rarely dull and I got a chance to use some of the most sophisticated equipment in the profession, but, when all is said and done, I don't miss the stress.  My co-workers were some of the most professional people I have met and they gave me a lot of slack, but it was time to move on.  I still drop in at the studio every now and then to cut a few commercials and remain available to help with election coverage and disaster assistance.  My new role as a teacher has been rewarding so far.
Now that I'm free a few more hours a week, I can concentrate on helping my xyl with the usual domestic chores and in expanding my modest amateur radio station.


As I've mentioned before, my radio shack is modest with a bunch of older rigs and homebrew antennas.  In the antenna category, I've been able to build a few verticals, loops, and dipoles that work very well, considering the postage-stamp size lot of my rental home.  I would prefer a decent 3-element beam on a 50-foot tower, but the proximity to power lines and neighbors rules that option out for now.  That project will have to wait until a new home is built on my xyl's property in the Puna District.  At this stage of the game, I'll make do with what I have.  So far, the 20-meter vertical dipole, the 40-meter under-the-house loop, and a 67-foot end-fed wire with counterpoise seem to generate enough contackts for now.  Most of antenna ideas are not original.  I've adapted a few very simple designs from ARRL and RSGB antenna books with some success.  I once had a 20-meter loop tacked to the shack's ceiling.  Nothing fancy, but it did get contacts at a low power level (less than 10 watts).  Presently, I'm working on the 67-foot long wire--mainly by improving the counterpoise system.  So far, the Drake MN-4 and the various baluns at my disposal seem to handle the impedance problems with the wire.   For more serious work, I find the homebrew 20-meter vertical dipole a useful and space-saving alternative to running radial wires all over the property.  My backyard is very small, so the radial field tends to be a bit haphazard.  When I used the 40-meter homebrew vertical, I found a tuned counterpoise helped a lot. Nothing too efficient here, but it did work.  For local Hawaii contacts, the 40-meter loop under the house (the house is on a post and pier system about 4 feet off the ground) seems to work very well.  Basically, the loop is a NVIS "cloud warmer" that covers the length of the entire state from Laupahoehoe on Hawaii Island (my qth) to Lihue, Kauai.  This might be a good antenna for those of us who run local or regional HF nets.  Most antenna books have a section on loops.  I haven't tried a magnetic loop, yet.  The November "QST" has an article on a small transmitting/receiving loop fabricated out of copper pipe and some hardy variable tuning capacitors.  Those of you more mechanically skilled than I may want to try one of these antennas if your space restrictions are severe.  I believe MFJ still sells a magnetic loop antenna that could help those of use with little space for antennas.  So, until school resumes in early January, I'll be fixing up the antenna damage done by our recent heavy rains.  This past Monday, Laupahoehoe received more than 8 inches of rain in a 12-hour period.  Although there was little moisture penetration noted in my various antennas, I will spend today checking all connections and rewrapping those that appear damp.  So far, there have been no coax leakages.  The 450-ohm twin lead remains in good shape and the 4:1 balun appears normal.  A few weeks ago I wrapped the balan and its connections in a large plastic bag to protect them from moisture.  I then put the bag into one of those plastic storage cabinets with a snap top to keep the weather out.  The entrance and exit holes for the antenna cables were sealed with a caulking compound.  Apparently, those precautions paid off.


With the exception of a Ten Tec Scout 555, all of my rigs are more than 20 years old.  For qrp work, I usually rely on the trusty Yaesu FT-7 which puts out a maximum of 20 watts.  I usually run the rig at 10 watts or less.  I keep the transceiver covered to keep dust out.  I've had no trouble with the circuit boards, which are easily cleaned.  The main HF rigs are an old Swan 100-MXA and an almost restored Kenwood TS-520 I received as a gift from the family of a Hawaii ham who passed away last year.  I also have a Drake TR-4 that needs a power supply.  I have the operator's manual for each rig, so I can do some rudimentary trouble shooting if I need to.  To date, the old rigs are steady and I treat them with care.  I try to keep them clean and covered when they are not in use.  I'm slowly putting away some of my funds to buy a rig that's more current.  I have my eye on an Elecraft K3.  For now, though, the rigs I have keep me busy.  I hope to do a little more operating during the holiday break.

Have a good holiday and take care if you're on the road.

Aloha es 73 de KH6JRM
Laupahoehoe, Hawaii--BK29jx