Build a Half Square DX Antenna

It's about as simple as they come. And it sure works f

William Van TUburg KG8AN 5198 West Valley Circle Portage MJ 49002-1932

Half Square Antenna

coax

Fig. 2, Feeding ihe cable and wire through the pre-drilled holes will iock ii in place with nothing but the force of friction.

The half-square antenna is a gain antenna, yet it is one of the easi-_ est, quickest types of antennas to build. This half-square configuration is a DX antenna that on 10m starts picking up signals from about 500 hundred miles out and gets stronger as the signaK come from farther away-

The physical size is a full wavelength long, divided into three sec-lions, You have a half-wave section on top, with a quarter wavelength dropped straight down on each end. To figure the length of an antenna you work a simple math problem. The formula is 1,005 divided by the frequency in MHz, This results in an answer for a full wavelength in feet.

Let's try a sample

First, let's go for the 10m phone section. The middle of the band I want will be 28A MHz, where the Novices/ Techs can operate. That's 1,005 + 28.4

= 35.387 feet of wire to start our anLeuna. That's 35' 4.5", You will need an extra three inches to allow for a smalt tie loop at the bottom end of the quarter-wave down legs. Each active quarter-wavelength i_s going to be 8.846 feet long (8* 10") so double the wire back to find the center and mark it with a piece of electrical tape. Ne\t, you need to measure 8.846 feet out from our tape marker toward the ends. The down legs w ill also measure 8,846 leel, plus the one and a half inches for the tie toop,

I have found that a broken white plastic lawn chair can be cut up to make very good antenna insulators. Cut rectangles 1.5 inches b\ inches and drill holes as shown in Figs. 1 and 2. t use a covered wire about #16 gauge, which helps keep down snow static. Siring the half-wave section in one hole, over and through the second hole, and down through the third hole towards the ground. On [lie other end. cut the wire at the corner of the top and down leg. Feed the wire across two holes to lock it in place. The other quarter-wave wire is fed up from the verticat ih rough the holes in the plastic to lock it in place as seen in ihe diagram.

Next, we need to feed the RG-58

Antenna Half Square

Fig, I. the whole half-square antenna complete with insulators made from broken lawn chairs.

through two holes to lock it in place; secure the ccnter connector lo the top horizontal section and then connect the braid or shield lo the down leg as seen in Fig, 2. Next, string the nylon antenna support cord through the end holes to support it between trees, towers, or buildings. The connections of all wires need to be soldered and then taped for weatherproofmg.

You need to keep the coax end of your antenna toward Lhc transmitter and at right angles if possible from the top wire. Now pull your antenna up as high off the ground as you can get it.

The height of your antenna off the ground will affect its tuning. Remember, the higher the frequency, the shorter the wire will be. Shorten the wire lop section and the legs to make the resonant frequency of the antenna higher. Make your adjustments about. 1/2 to 3/4 inches at a time. If you change one leg by 1/2 inch, the top section will have to change by one inch. Make uny required adjustments to find the center frequency and it's ready to transmit. Tic a loosely dangling retainer cord to each of the down leg loops to keep il from blowing over the top wire.

The maximum radiation is broadside, so an antenna strung north and south will do best to the east and west. I use this type of antenna at home on 10m, and also during Field Day on 20 from Kalamazoo County, Michigan,

Some of the half-square advanlages are about 4 dB gain, a low radiation angle, good noise-canceling characteristics, both vertical and horizontal polarization, and low cost,

I've talked ail over the world with this antenna, so be sure to let me (and Wayne) know how it does for you!

Editor s note: You can greatly simplify the trimming of the antenna if you cut it a little long to starty then find where it resonates (minimum SWRj.Now you can make a simple ratio of the antenna length divided by the resonant frequency equaling the desired length divided by the desired frequency. This way, it takes just one trim session and you 're in business without alt that half inch at a time from each part of the antenna. For example, if you come out 8" too long f just cut 2" from each quarter-wave section — 4U from the horizontal section and 2" from each vertical leg, B

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Responses

  • Peony
    How to make a half square antenna?
    8 years ago
  • jak burns
    How to build a Half square antenna?
    8 years ago
  • Suvi Sundqvist
    What balun for a halfsquare?
    9 months ago
  • MEDHANIE
    How to keep half square antenna from blowing?
    8 months ago
  • Lavinia
    What balun do you use on a half s quare antenna?
    4 months ago

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