Saturday, April 28, 2012

Simple Antennas for the Radio Amateur--a continuing series

How would you like to build a cheap, easily erected, and efficient antenna for your small yard?  I've pondered that idea over the past several days after a cold front and its associated high winds made a mess of my temporary, homebrew vertical next to my garage.  Since I had a few days off from my substitute teaching assignments, I decided to build another sky hook with materials I had in my "junk box."  I still had a good pvc mast, about 100 feet of number 14 housewire, and an extra 4:1 balun stashed in the corner near the washing machine.  Along with 50 feet of 450 ohm twin lead and about 20 feet of RG-6 coax, I was in business.

The antenna would be an inverted "vee" inspired by a variety of articles in the ARRL Antenna Book, various amateur radio forums (e.ham, net), and a 1998 paper entitled "The $4 Special" by Joe Tyburczy, W1FGH.  The antenna won't rival a mono band beam on a 50-foot tower, but it will provide hours of good contacts at a small cost.  Since I'm financially conservative by nature and now settling into a "semi-retired" state, expensive antenna projects will have to wait until the xyl and I move to our property in the Puna District (20 miles southwest of Hilo).  With that in mind, I spent most of this morning lowering my hastily made novice class dipole (as mentioned in the last post) and reusing the parts for the inverted "vee".  I was able to attach two, 33-foot lengths of  #14 gauge  house wire to each side of the 450-ohm twin lead with an angle of about 120 degrees separating the wires.  I ran 50 feet of twin lead to a 4:1 balun attached to the garage.  The balun was attached to approximately 20 feet of RG-6 coax, which then ran to a Drake MN-4 ATU.  A short 3-foot jumper cable made from RG-6 connected the ATU to the old Swan 100 MX. 

The antenna works well between 40 and 10 meters.  The ATU is happy, the old Swan is happy, and I am happy.  In the original article by W1FGH, the cost of the antenna was around $4.  But that was back in 1998.  Nowadays, everything is more expensive.  Nonetheless, I was able to make this antenna out of materials I had in the shack and in the garage.  Since I'm a packrat, I had no trouble finding wire, connectors, rope for guy wires, cable, twin lead, and tools to finish the project.  And like my previous vertical antennas, I can lower the structure and its elements when I'm not using them.

For my modest station, this inverted "vee" provides plenty of contacts from this isolated chain of islands in the Central Pacific--even at qrp levels of 10 watts or less.  When the neighbors aren't home, I run a little more power (around 50 watts).  The mast is painted a light green to match the local surroundings.  The antenna is barely noticeable from the street.

Building the inverted "vee" was lots of fun and it gave me plenty of exercise outdoors.  Antenna and kit building are some of the areas we amateur radio operators can explore without spending too much money.  My favorite radio store is the nearest Home Depot or Ace Hardware Store.  Of course, there are some specialized parts that must be ordered from mainland sources (Mouser, Digikey, Jamco, and others), but, generally, a well-supplied junk box will give you most of the parts you need for simple antenna projects.  Besides, one gets a sense of accomplishment and satisfaction from building something from "scratch". 

That's all for now.  A few household chores remain before I can fight the qrp on the lower edge of 40 meters.

Have a good weekend!

Aloha es 73 de KH6JRM--BK29jx15