Beverage antenna matching transformers

We've built about a dozen of these to customers orders, so it is time to include them as part of our regular product range.

These units are passive matching terminations for Beverage or similar receiving antennas. They consist of a 9:1 toroidal wideband transformer inside a weather-resistant box, for 50:450 ohm match, or 70:630 ohm match, or whatever...We have recently (Nov 2005) improved the units further. We were using a simple tapped autotransformer on a ferrite core. This gave no DC isolation between the primary and secondary. We are now using a specially-selected ferrite bead, to give DC isolation, thus providing  better performance. Recently we did an A/B comparison of the new transformers against the old. There is a significant improvement. At the new GW3YDX QYH, there is not as much land as at the previous QTH. The only place to put a USA Beverage was up a drive, with the feedpoint running under, and parallel to the transmit dipole. This is absolutely not the place to put it, because noise picked up on the dipole is easily induced into the Beverage element. Results with the old-autotransformer system were very disappointing, the Beverage rarely being better than the transmit antenna. When a new isolated-transformer was used, the Beverage started working as it should.

There is a coaxial socket for the feedline (either SO-239 or N-type at customes choice) and the antenna and ground connections are by stainless-steel M4 screws, lockwashers and nuts. The transformer has been designed for a good match between 1.5 and 10 Mhz.

Price - just £35  (56 Euros) plus carriage

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Our short notes on Beverage antennas

For people who have not used a Beverage on the LF bands, it is like going from a G5RV to a 6 element monobander for receive. It's well worth trying. You don't need that much land,either.

The matching transformer for the feeder cable is absolutely necessary. We tried without, directly into coaxial cable, and it is useless. Also very disappointing is a Beverage without the terminating resistor.

In practice we have found that two paralleled 1K ohm CARBON resistors work as well as anything for the distant resistive termination. After having tried all sorts, the preferred arrangement is for the Beverage wire to slope upwards from the transformer for 50ft to the average height, and downwards for about 50ft from the last support to ground level, where the terminating resistor is located. The Beverage element wire has been either some very nice ex-BT telephone dropwire (18 gauge conductors plus very thick plastic insulation) or bell-wire (rubbish stuff, very thin, poorly insulated and stretchy). The rubbish wire seems to perform as well as the 18 gauge quality wire but sags rather a lot! I am told that insulated wire is less prone to static pick-up than bare wire, but I have never tried it.

Beverage element lengths - you really need 250 ft or more to make it work. Best length seems to be about 800ft for 160m if you can manage it. 520 ft is also good. Some years, we have a 800ft Beverage on the USA, a 520 ft one on JA, and a 1000 ft one on South Africa / USA long path. The longer units work better on 160. For supports, the easiest and cheapest are bamboo garden canes. You need to use thin wire with these (as they will break with sideways wind pressure from thick wire), supported every 50ft or so to avoid excessive sag. Every 150ft, it is a good idea to use two canes tied together in an A-frame to give lateral support.  Between 3-5ft off the ground  for the wire seems pretty good. We have tried up to 20ft  high to clear cattle etc, and the higher wires are definitely inferior. For coaxial cable, we have used RG58, RG213, TV 75 ohm coaxial cable, or even a mixture, in runs up to 700ft long. A tuned pre-amp at the receiver end of the feeder cable (even better at the transformer end if you can manage it) is really beneficial with long feeder runs. Untuned pre-amps are a bit dodgy as they tend to pull in all sorts of unwanted signals.

For feeder cable, purists and millionaires go on about Heliax or double-shielded RG213 (I wish!) but a TV co-ax 256 ft Beverage is a lot better than no Beverage at all.

For a grounding system, you need a fairly good system at the matching transformer end, at least a good 3ft copper earth stake and maybe a couple of  short radials at 90 degrees to the Beverage element. At the resistor end, remember that the Beverage is terminated in about 500 ohms of resistor anyway. Any ground series resistance with that is not going to be a big deal. Before now we have used a aluminium 2m yagi element pushed in to the ground about a foot for temporary installation, and that worked fine!

There are loads of articles on the internet on how to build very good Beverage antennas, much better than I do, but....

Remember that your goal is not electronic perfection, but an improvement in signal-to-noise ratio!