Optimizing the Beverage Antenna
The Beverage antenna is one of the best receiving antennas for the long and medium wavelengths. It has been around for a long time and reams of paper have been written about this antenna. Having used several Beverages at a commercial marine ship to shore site, I can attest that it is a very good receiving antenna.
I have known several hams that operated on 160 meters with the Beverage as their receiving antenna and they too reported excellent results. While about to make repairs to their Beverages, they were curious as to how to optimize these antennas. So, I set about to find out how they could get the most for their efforts. The results were interesting to say the least.
Figure 1 displays the Height versus the F/B ratio and shows the variation in F/B ratio in dB for height increase and F/B ratio. The maximum F/B ratio was at 405 ohms where the F/B ratio was 50 dB.
The above graph shows there is a definite peak of F/B ratio at seven feet (2.1336 m) of height. This makes putting up this type of antenna rather easy as the height requirement can be met with 10 feet (3.048 m) of PVC pipe and with 3 feet (.9144 m) of the pipe stuck in the ground.
Figure 2 shows the load versus F/B variation and that the peak F/B ratio occurred at 405 ohms.
So with an antenna height of the antenna set at 7 feet (2.1336 m) and a termination load of 405 ohms the maximum F/B ratio is 50 dB.
Figure 3 is of height versus load and shows how the terminating load resistance changes slightly with load from 3 feet to 12 feet (.9144 to 3.6576 meters)
Antenna Specifications
The Beverage used for this example is a two-wavelength 160-meter (1040 feet 316.992 m) antenna and the soil conductivity is that of coastal plains, high conductivity moist soil. Wire size was #16 copper stranded wire, with a single conductor.
If you want to optimize your Beverage, but the height is already determined by what you have installed, the best way is to go to the far end of your antenna and attach a non-inductive potentiometer of 1,000 ohms in place of your load. Then have a small signal source turned on directly to the rear of the antenna. With someone watching the receiver, you can vary the potentiometer for maximum attenuation of the signal. You will have to have some method of communication so you can be told when you hit the maximum null.
After you find the null point, substitute a fixed resistor for the value that the potentiometer was set for max null. A RF choke should be added in parallel with the resistor to bleed static charges off of the antenna. Add a RF choke at the receiver end also for the same reason. Wind-blown dust and snow, and even rain, can cause a charge to be built up on a long antenna like this and can increase to levels that will damage the equipment. So some sort of static drain is mandatory. The antenna used for this test was destroyed some time after the tests were done, but the results were more than adequate for 160-meter DX chasing.
Good 160 DX
If you have the room, a Beverage is one of the best antennas for160 meter DX, as it is very directional and has a fairly low angle of radiation for reception. But, since these antennas are not very efficient, they are seldom used for transmitting. However, for reception the lower efficiency is not that important because the directional characteristics help the reception greatly. If you decide to install one of these antennas, remember the Beverage efficiency is dependent on the type of ground soil present. Poor soil, like a desert, will give better results than if the antenna was installed over a marshy damp soil. However for the most part, the Beverage will do an adequate job despite the many variations in soil that exist.
Later on, the design of more efficient Beverages for some of the higher bands will be undertaken and reported here in antenneX.
Originally posted on the AntennaX Online Magazine by Richard Morrow, K5CNF
Last Updated : 25th April 2024