|Modern Beverage Receiving
Antenna Construction and Installation
One of the most beneficial station antennas that offers good low noise directional
or non-directional performance at a very affordable price is the beverage, or "wave"
antenna. It is constructed from a single wire, end-fed from the station end, and
elevated 5-10 feet above ground on insulated standoffs.
Beverage antennas fed through a wideband impedance converting transformer offer
broadband low noise performance for low to mid-frequency applications in the 0.5
to 9 MHz range, more or less. If you're interested in directional performance plan
on erecting a beverage antenna in a straight line toward the desired direction of
at least 1 wavelength at the operating frequency of choice. The longer the wire
is in that direction the more directive the antenna becomes. Essentially the beverage
is a piece of unshielded parallel line transmission line in the 400-600 ohm range,
respective to earth. Feeding the antenna requires a broadband transformer which
is simple to wind and is featured in many technical books and articles. But here
are a few observations we would make that you won't find in published literature,
or at least in few of them...
- In terminated beverages after the installation is done check the impedance
matching and load resistor choice by simply inserting about 1 watt or so of power
into the system and measuring the match system with a simple VSWR measurement.
Sweep the frequency range of desired use in this manner and you can see if the
impedance transformation and resistance used is correct, or if some alterations
have to be made. We found at the I.C.E. factory station that for our 600-800
foot terminated straight beverages resistance and matching of 450 ohms worked
best, offering a near 1:1 match from 1 to 30 MHz
- Be sure to include blocking-type lightning protection in the match system to
prevent developed voltages from destroying your radio equipment. Blocking the
DC path with a .01 capacitor is beneficial if a drain-to-ground matching system
is employed. A beverage of only a few hundred feet can be electrified up to as
high as 10,000 volts respective to ground with an overhead cloud-to-cloud lightning
blast (we know - we measured it).
- Be sure that from the feedpoint to the wire that the wire ascends slowly to
its regular height of travel down the rest of the antenna. Don't feed the antenna
and then go vertically up 10 feet, turning horizontal for hundreds of feet or
the antenna will look like a vertical receiving antenna partially and some of
the low noise and directivity effects will be compromised.
- Use steel, galvanized wire where possible. Since the antenna is voltage fed
(high-Z) there's no advantage to be realized from using copper wire. Contrarily,
copper is soft and stretches easily, causing sag. Also, it is easy to break if
tree limbs or ice land on the wire span, causing the copper to sag further or
break. Best choice -electric fence wire used by cattle farmers. It's #18 #19
in size, galvanized, solid steel with a 1,000 pound strength, and can take a
lot of punishment. It's also 60-80% cheaper than copper, costing around $8.00
per quarter mile (1,250 feet) and sold in farm stores and some hardware stores.
- Use carbon composition or flameproof non-inductive resistors for terminating
the beverage, and use 10 watts or better of power handling capacity. During transmit
your beverage can be really hot with RF and can easily burn out small resistors.
The larger power resistors also help prevent lightning burnout. Wirewound power
resistors work fine if the frequency limit of the beverage is less than 5 MHz
or so. Including a gas-discharge unit in the 75V range is helpful.