Sunday, February 5, 2012

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

This has been an exciting two weeks.  First, my long-term substitute teaching position has been confirmed until June.  Laupahoehoe High and Elementary School is converting to a charter school, so many faculty associated with the state of Hawaii Department of Education may be transferring elsewhere.  So, until the new school board gets in place, there will be no new hires, and that means substitute teachers such as I will be in demand until the change over at the end of the school semester.  So much for an easy retirement.  The work with special education students is demanding, but, on the whole, very satisfying--especially if a student finally "gets it" and begins to learn on his/her own.  During the past few weeks, I haven't been able to run the old Swan 100-MX very often, with the possible exception of a few hours of cw late at night.

And second, the weather has been unusually warm and dry these past three weeks--a perfect time to work on antennas and maintenance.  During the first three months of the year, tradewind showers usually soak the windward side of Hawaii Island very well.  But this year, most of the rain has been spotty, usually falling along the upper elevations of Mauna Kea or Mauna Loa.  To date, Laupahoehoe has received only 1/3 of its normal monthly precipitation.  On the west side of the island, a persistent drought continues, with both coffee farmers and ranchers suffering the most.   I'm taking advantage of the good weather before anticipated rains come sometime this month.

My 20-meter dipole in the backyard continues to perform well.  With the 450-ohm ladder line and the trusty Drake MN-4, I've been able to use the antenna from 20 to 10 meters.  Fifteen and ten meters have been productive from early afternoon until a bit past sunset.  My 40-meter vertical along the border with my neighbor's house works as expected.  And the 40-meter loop under the house has done a satisfactory job of maintaining communications throughout the state of Hawaii.  The loop in its current configuration is used as a NVIS antenna for local nets. 

If you are short of cash (who isn't these days) and are a bit reluctant to "roll your own", you may want to examine several interesting antennas in the latest catalog from MFJ.  What caught my eye is something the company calls the "Big Stick 8-Band Vertical Antenna" on page 75.  The stick is a 17-foot stainless stell collapsible whip paired with an adjustable high-Q air wound coil using a "Guanella balun" that the company claims decouples the feedline and keeps the operating position RF free.  The MFJ-2286 comes with a couterpoise kit.  All you need is a 1/4 or 1/2 inch pipe or mast to attach the "stick" and you're ready for coverage from 7.0 to 55.0 Mhz.  MFJ also sells a tripod you can use to position the antenna in your back yard.  I haven't tried this antenna yet, so "your mileage may differ".
This arrangement is considerably cheaper than the popular "Outbacker" verticals I see in many amateur radio magazines.  The listed price is $99.95 plus shipping.

As for myself, I prefer to make my own antennas out of wire, pvc pipe, wooden spars, and locally available materials.  My antennas are not works of art, but they do get contacts.  Now that 10 meters is opening up in the afternoons in the Central Pacific, I may just erect a homebrew antenna to cover that band.  I have several pieces of pvc pipe that be bolted together to form 33-foot mast.  I could run some RG-6 coax up the pole to an inverted vee (8' 2" on a side) and see what happens.  Back in the day when CB was king (yes, I was one of those guys), I used a similar arrangement to cover the Hamakua Coast on channel 12.  Running the legal limit of 4 watts or so, I managed to get ground wave coverage up to 15 miles or so, depending on how the signal penetrated the gulches along the coast.  That wasn't too impressive, but it did whet my appetite to get my novice license back in 1977.  And as the old saying goes, "the rest was history."  I've used modified CB antennas since those times to work 10 meters when the band was open.  Of course, a 40-meter vertical, twin lead, and the Drake MN-4 makes 10 meters a snap to operate, but, there's nothing like making an antenna specifically designed for your band of choice.  My junk box has an ample supply of #14 wire, RG-6, insulators, and connectors, so the project should be fun and take little time to complete.  Even an old 102" CB whip can be trimmed to work on the 10 meter band. With a few radials or a decent counterpoise, your old CB antenna can be a useful antenna for the fickle 10 meter band.  Most antenna handbooks provide examples of easy to make antennas for this exciting band.

That wraps it up for this week.  I hope to get in a few more hours of operating time after my class duties are done.  Meanwhile, get on the air with an antenna you've designed and built.  It's fun and educational at the same time.

Thanks for dropping in!

Aloha es 73 de KH6JRM (Russ)
Laupahoehoe, Hawaii--along the beautiful Hamakua Coast