Saturday, September 7, 2013

In Praise of Wire Antennas. Post #226

Every now and then it's good to stand back and analyze what you've done to your antenna farm.  Is your antenna arrangement fitting your goals? How easy is it to build and maintain the structures that connect you to the world?  Is there a way to make your antenna more efficient without spending a lot of money?  I came to such a crossroads this weekend as I surveyed the rural Puna District home my wife and I are remodeling for our permanent home.

After years of living in rental apartments and homes with restrictive covenants, I will at last have an acre of land to build some full sized hf antennas.  I will admit that I've learned a lot about stealth antennas and low power operation during my 36 years as an amateur radio operator.  But now, I have some real space to build antennas with real gain.

My main problem was deciding whether to buy a tower, a set of mono band beams, and sophisticated antenna rotating equipment or to stick with my faithful wire antennas which have produced excellent results despite space restrictions.

While I pondered this issue and the expense involved, I ran across an interesting article on wire antennas by Lou Gionvannetti (KB2DHG) in the 07 September 2013 issue of eham.net.  Lou, who apparently had to give up towers because of health and financial problems, decided to make his own wire antennas.  Armed with a homebrewed off-center dipole (G5RV), Lou managed to reinvigorate his interest in amateur radio, contact many new friends, and save a lot of money in the process.  His article reaffirmed my belief in the pure joy of designing, building, and using home made antennas.  If my financial situation were a bit better, I wouldn't mind erecting a decent tower with several mono band yagis.  There are no restrictions on my new property and there is certainly sufficient space to "plant" an aluminum forest.  But, I stopped climbing towers when I left the broadcast business two years ago.  And I have no desire to strap on a climbing harness and a hard hat again.  So, my avenue was quite clear--build your own wire antennas and learn a lot in the process.

I decided early on that only local materials found in nearby hardware or home improvement centers would be used for masts, antenna wire, coaxial cable, insulators, and ground rods.  The only thing I would have to order would be 450-ohm ladder line, some Budwig coaxial center connectors, and torroids, if needed.  My junk box contained various adapters, clips, tape, ceramic insulators, soldering equipment, and tools.

So, with a renewed faith in my ability to erect the antenna facility of my choice at a reasonable price, I began the building of the antenna "farm."

Before I started the long-term project, I consulted the various antenna books on the shelf of my radio shack to get an idea of what I was up against.  "The ARRL Antenna Book" is a good general source of antenna information and it became my unofficial guide for this antenna effort.

As of today, 07 September 2013, my antenna farm looks like this:

One 80 through 10 meter "doublet" (horizontal half-wave dipole), with a resonant frequency of 3.750 MHz. This antenna, fed with 450-ohm ladder line and connected to a W9INN 4:1 balun and a Drake MN-4 transmatch would serve as a multi-band, general purpose antenna.  RG-8X coaxial cable would run from the the balun to the transmatch and then on to the Swan 100 MX transceiver.  The antenna is stretched between two Norfolk Pine trees, approximately 50 feet (15.24 meters) above ground level.    This antenna has performed very well with the old Swan 100 MX running 50 watts or less.

One 20 meter half square antenna (see previous post on this topic) with a resonant frequency of 14.200 MHz.  The broadside pattern of this two mast antenna joined by a half wavelength horizontal phasing line is helping me get into the mainland U.S. and the South Pacific without difficulty.  According to what I've read, this antenna is capable of producing a gain of 3.8 dBi.  All I know is that it works well for me.  My feedline is RG-8X coaxial cable attached to the top of the left hand mast--the point of maximum current.

One full wavelength 40 meter vertical loop supported by two telescoping fiberglass masts.  I get 40 through 10 meter coverage when I feed the loop with 450-ohm ladder line.  I use the loop for mostly local nets, although coverage is sometimes surprising on 20 and 15 meters.

One 5/8 wavelength vertical with six elevated radials for 10 meters, with a resonant frequency of 28.4 MHz.  Although this antenna should show a gain of approximately 3 dBi, the band has been inconsistent and noisy.  Local Hawaii Island contacts have been useable, most likely due to ground wave.  I'll keep this antenna in the air in case the band opens up.

One inverted vee antenna supported by a single telescoping fiberglass mast.  The vee is cut for a resonant frequency of 7.088 MHz (the frequency of the Hawaii Afternoon Net).  The antenna is fed with 450-ohm ladder line and can be used on all amateur radio frequencies from 40 through 10 meters.

One 40 meter delta loop fed with 450-ohm ladder line in the lower left hand corner of the loop.  The loop is cut for a resonant frequency of 7.088 MHz and can be used from 40 to 10 meters.  Like the full wavelength vertical loop mentioned above, the delta loop is quiet and provides excellent state wide coverage.  As with all of my wire antennas, I rarely run more than 50 watts from the old Swan 100 MX...most of the time, I tend to run 10 to 20 watts output.

For a power supply, I use solar cells to charge a large deep cycle marine battery.  I can use the electrical mains if I have to.

Here are a few things I've learned from building my own antennas:

It's fun.  If the antenna fails to perform as expected, recycle the wire, redesign the antenna, and build a new "skyhook."

Most of my materials can be bought locally.  Some types of coaxial cable and ladder line must be bought from outlets on the U.S. mainland.  Sometimes, I can get left over RG-6 cable with F connectors from the local cable company.  With F to UHF adapters from Radio Shack, I can use this 73-ohm cable in the shack.  I've used RG-6 with no problems on my dipoles and inverted vees.  The Drake MN-4 seems to handle the small mismatch very well.  So, if you don't have a supply of RG-8X, RG-8, or RG-58, consider using RG-6.

Antenna wire can be anything from #14 AWG housewire and #18 AWG speaker wire to bell wire and "zip" cord.  You can buy wire at home improvement centers and hardware stores.

PVC pipe can be used for masts.  You can also order fiberglass masts from MFJ and DX Engineering.

You can make your own 4:1 and 1:1 baluns or you can order them from HRO, AES, or any online distributor of amateur radio equipment.

You can get a large amount of satisfaction from building something that gets you on the air.  Antennas are one of the few areas where you can experiment at a modest cost.  Most antenna builders I know are also assembling kits and accessories for their amateur radio stations.  I must admit to a bit of slackness in this area.  I've built a field strength meter and a few commercial kits, but nothing as complex as a transceiver.

Meanwhile, I'm learning a lot by actually translating antenna theory into practice.

If you have the resources, go for the tower and the stacked mono band yagis.  Your signal will surely be noticed.  On the other hand, if you're on a fixed retirement income such as I, homebrewing your own antenna may be the way to go.  There are plenty of reference materials in books and on the internet to help you build that one of a kind antenna farm.  Good luck...enjoy the experience.

REFERENCES:

http://www.arrl.org/files/Technology/tis/info/pdf/0683033.
http://www.hamuniverse.com/randomwireantennalengths.html.
http://www.dxzone.com/dx28476/ham-radio-wire-antenna-tips.html.
http://www.eham.net/articles/30550.

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

Thanks for joining us today!

Aloha de Russ (KH6JRM).

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.