How long should a random-wire antenna be?

How long should a random-wire antenna be?

It is important to use a counterpoise. A standard recommendation (see QST, March 1936, p. 32, “An Unorthodox Antenna”) is an 84′ long end fed and a 17′ long counterpoise (6.5′ for 20m)….Wire Lengths for Various Band Combinations.

Group USA Bands
a 40-30-20-15
b 40-30-20-17
c 40-30-20-17-15-12-10
d 80-40-30-20-17-15-12-10

How do you use a random-wire antenna?

One end of the wire attaches to a tree, pole or other support, preferably at a high point. The other end connects to the random-wire connector on a suitable antenna tuner. You apply a little RF and adjust the antenna tuner to achieve the lowest SWR. That’s about all there is to it.

What is one disadvantage of a random-wire antenna?

One disadvantage of a directly fed random-wire antenna is that you may experience RF burns when touching metal objects in your station. The simple single wire length of the random-wire antenna acts as both feed line and antenna and is directly connected to the transmitter.

Does a random-wire antenna have to be straight?

The wire may be straight or it may be strung back and forth between trees or walls just to get enough wire into the air. Due to the great variability of the (unplanned) antenna structure, effectiveness can vary wildly from one installation to another.

Are end fed antennas any good?

End fed wire antennas can work very well under many circumstances. They have some disadvantages, but with careful installation, they can work well and be particularly versatile offering multi-band operation.

What is the purpose of a counterpoise?

The counterpoise functions as one plate of a large capacitor, with the conductive layers in the earth as the other plate. Since the radio frequency alternating currents from the transmitter can pass through a capacitor, the counterpoise functions as a low-resistance ground connection.

What is the impedance of a random wire antenna?

Impedance is highest on the lowest band. Note it is 6850 ohms on 80 meters, decreasing to 1360 ohms on ten meters. This is because more and more half waves are being fed from one feedpoint with increasing frequency….Counterpoises.

Advantages Disadvantages
inexpensive require a tuner or matching system

What wave is a CB?

The CB portion of the spectrum begins at 25.01 megahertz, so a full wavelength antenna would be a bit more than 39.34 feet long. That’s obviously a little long to attach to your bumper, so people tend to use antennas that are a fraction of the wavelength: 1/2, 5/8, 1/4 and 1/8 are all common wavelengths for antennas.

Why do pickup trucks still have antennas?

Pickups have an antenna, instead of the standard glass build antenna for a couple of reasons. Namely being for design, strength of signal, and ease of repair!

What is a random wire?

A random wire is exactly that—a piece of wire that’s as long as you can possibly make it. One end of the wire attaches to a tree, pole or other support, preferably at a high point.

How do you tune an antenna with a random wire?

One end of the wire attaches to a tree, pole or other support, preferably at a high point. The other end connects to the random-wire connector on a suitable antenna tuner. You apply a little RF and adjust the antenna tuner to achieve the lowest SWR.

Can I use random wires for antennas?

Random wires are fine for low-power operating, however, especially in situations where you can’t set up a vertical, dipole or other outside antenna. And you may be able to get away with higher power levels if your antenna tuner is connected to a good Earth ground.

Do you need an antenna tuner for a 50 ohm transmitter?

Now, admittedly, with standard 50-ohm transmitter (transceiver) output impedances, you will need an antenna tuner most of the time. My favorite is a simple pi-network (two variable caps, one on either end of a tapped inductor) but most commercial “T” or “L” designs work well.