Open-Wire-Fed Antennas

You will also find information about building your own ladder line here: D-i-Y Ladder-Line .

​These three different feedline types are explained in detail on the page OpenWire Info .

meaning the narrow 300 Ohm commercial balanced feedline. Note that there are high quality versions designed for use with transmitters, and cheap TV quality versions designed primarily for receiving. ONLY USE the high quality versions, unless you are running QRP.

meaning the narrow 300 Ohm commercial balanced feedline. Note that there are high quality versions designed for use with transmitters, and cheap TV quality versions designed primarily for receiving. ONLY USE the high quality versions, unless you are running QRP.

meaning the commercial feedline (typically from THE WIREMAN) with a nominal impedance of 450 Ohms. (Be aware that it is often closer to 400 Ohms).

meaning the commercial feedline (typically from THE WIREMAN) with a nominal impedance of 450 Ohms. (Be aware that it is often closer to 400 Ohms).

meaning two independant wires separated by insulated spacers and usually having an impedance in the range of 400 to 600 Ohms.

meaning two independant wires separated by insulated spacers and usually having an impedance in the range of 400 to 600 Ohms.

In these cases I will explain, using the following 3 terms:

Unless otherwise specifically stated, I will use the generic term "Openwire" to mean any and every balanced feedline mentioned above.

What this antenna is:

A Multi-Band WIRE Antenna

Fed in the Center with Openwire

Requiring an Antenna Matchbox on All Bands

Usually it is a simply a Dipole, fed in the middle with openwire feedline.

Initially these antennas were one half wavelength long on the lowest operating frequency.

Later, shorter versions were found to work successfully, with a few concessions that we will discuss below.

"Dublet" was the common name for this antenna when it was not a half wavelength long on the lowest operating frequency.

Originally these antennas were called "half wavelength Hertz Aerials" and were fed with a single wire. Later they were fed with two wires (which I generically call openwire) and called a Double-Zepp Aerial (or Antenna) because they could be viewed as being two single-wire Zeppelin antennas, fed with a common balanced feedline.

These antennas REQUIRE the use of an Antenna Matchbox on all bands.

They not only require an antenna matchbox, they also place some fairly significant requirements on the match box (e.g., very broad impedance matching range, from single digit Ohms up to multiple thousand Ohms, must be capable of coping with very high voltage as well as very high RF current).

DOUBLET SIZE:

Most people believe that the antenna should be a resonant half wavelength. This length has the advantage that when resonant, it is (theoretically) purely resistive. However it also has disadvantages, specifically the impedance on the harmonic bands is VERY high; several thousand Ohms. This can be quite difficult to match.

Common sizes for the 80m Doublet:

132 ft. (plus/minus - depending on where the user wants it to resonate within the 80m band)

111 ft.

100 ft.

88 ft.

66 ft.

Of these, I have personally used 132, 111, 88 and 66 ft.

The longest one, the full half wavelength was used primarily at home.

When traveling I tended to use the 111 ft. when I had space, otherwise the 88 ft.

At one home QTH where space was limited, I had to use the 66 ft. version, even for 80m.

Fundamentally and HIGHLY SUBJECTIVE, I can say the following about performance:

Using the full size (132') as base, I will give it a 10.

The 111 ft. version seemed to work just as well. I will also give it a 10, although in theory it's probably more like 9.5. You won't tell a difference.

I would give the 88 ft. version an 8 8.5. I noticed in contests that I often had to call a couple of times more often in order to work the DX multiplier, but it worked very well.