Thursday, December 12, 2013

Build a Beverage Antenna - by Joe WD0M

The following is a re-print from  WD0M's website

Beverage Antennas
for the Low Bands
- a RECEIVE ONLY Antenna
The Beverage antenna is an "ancient" antenna, named after the gentleman who discovered it. Essentially, it is a VERY LONG antenna, typically placed at a level of 10 feet or less above ground. The Beverage antenna is referred to as a "wave" antenna, and is directional, if terminated with a resistor, in the direction it is aimed.

Since I could have small animals wandering through, placing it at a height where the critters could end up wearing it wouldn't improve their demeanor, nor reception on the low bands. I discovered that when placed ON THE GROUND, it is known as a "snake" antenna. And that is what I did. That flies in the face of most antenna concepts, where higher is better. But I'll be darned if it doesn't WORK!

The benefit of this antenna is that it eliminates or reduces the static and leaves only the signals you're trying to hear , providing a better signal to noise ratio. I use it on 160 - 80 meters exclusively as a receiving antenna. It also improves 40 meter reception, but not nearly as dramatically.

The diagram (right) demonstrates the general layout of a low band Beverage antenna system that may be switched for improved reception in two directions. If you terminate the wire at the end, it will be directional, favoring the signals coming to you from the direction it is pointed.

If you do NOT terminate the antenna, then reception will be from both directions for that particular Beverage wire. Having two Beverage antennas, selectable with a relay, lets you choose the direction you want to listen to.
There are very few "tricks" to putting this antenna together. At the far end (one of mine is aimed toward Europe) of a 275 foot long #14 wire, solder a 470 ohm, 1/2 watt non-inductive (not wire wrapped) resistor to the end of the wire, and then connect it to a good ground system.

An antenna analyzer will let you determine the appropriate terminating resistance (470 ohms is a good start), as well as the exact number of turns of wire on the toroid to provide a 1:1 SWR.

Construct a simple matching transformer consisting of a number 43 or 77 toroid and 12 turns of wire wrapped around it. Leave a tap (bare wire) after the third turn to provide a ground connection for both sides of the transformer. The earth serves as the common "return" for the ground side of the antenna. The transformer matches the 470 ohm impedance of the Beverage antenna to your 50 ohm receiver.
At the receiving end, I attached the ground wire from the toroid to the single point ground rod for my station. After I found out how well the Beverage works to reduce static (QRN), I put in a second Beverage aimed toward the northwest and use a small relay to switch between them. The second Beverage isn't terminated, and I can hear stations to the northwest, as well as stations in Central and South America FAR better than I had imagined with any of the other 160 and 80 meter antennas I'm using.

Final thoughts: This is a RECEIVE ONLY antenna. Don't be too concerned about obtaining a perfect 1:1 SWR - even with a 2:1 or higher SWR, you'll notice very little difference in the received signal strength. I encourage to give it a try and not be too conerned about theory - practical results are what matters.

Since 160 meters is primarily open during the winter, I leave the antennas on the ground until spring arrives - pick them up - and put them back in the fall. Since the "snake" antenna isn't mounted on supports, it's easily moved as well, to give you coverage toward different parts of the world. Give it a try - and have fun!


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