Survival Tomorrow Article
THE JOURNAL OF SELF-RELIANT LIVING
Rubber Duck Antennas
Carl E. Krupp, N7EZY
The rubber duckie is the most common antenna in amateur radio, as there is one sitting on the top of every handhled radio in the world. They are also among the most misunderstood antenna, for few people realize how inefficient they are, preferring instead to assume that some electronic wizardry has been performed so that they will do things that the laws of physics say can't be done!
The fact is that most two meter rubber duckies don't perform as well as a plain 19 inch ground plane antenna, though we have found one antenna company who have managed to make their duckies much better than those from the competition.
THE BIG TESTAs you can see from the photograph, we got virtually all of the models of the rubber duckies sold in America so we could see what was available. In so doing we tripped into the fact that one manufacturer makes many of the ducks available, and that they are made for commercial radio service 150-160 MHz band, rather than the 144-146 ham band. Since they are cut fir the wrong frequency they are really poor performers!
HOW WE TESTWe use a noise bridge receiver to find the exact frequency the antenna is tuned to, and also the input impedance. A full explanation of how to use a noise bride is available in the ARRL handbook.
The noise bridge we use is unique in that you can use it as high as the two meter band, for most will not work well above 30 MHz. It is their 1-150 MHz model and in available for $68 from Tennatest, owned by Gordon Adams, 1025 wildwood road, Quincy, Michigan 49082. You can write him and he will be happy to ship you his noise bridge via U.S. mail COD, but don't ask for UPS… for he is in a town of just 1500 people, just north of the Indiana-Ohio border, and there are no good sized cities or UPS offices within miles and miles of his town.
Here is another classic example of someone who developed a better product than was available on the market and is selling it by direct marketing.
Once we have established that the antenna is correctly tuned, then we use it side-by-side transmissions to stations several miles away who have accurate signal strength meters. We usually try to have several stations listening and recording results so we eliminate any funny atmospheric or local conditions that might influence the tests.
THE BEST RUBBER DUCKIEAfter going through the motions for all the ducks, only the products from the Smiley Antenna Co., Inc. were correctly tuned for both frequency and input impedance.
THE STUBBY DUCKThe four inch tall duck, usually called a stubby duck performed as well as a standard sized duck from the other manufacturers, proving that tuning the duck to the correct frequency has a very beneficial effect.
THE STANDARD DUCKThe regular sized duck, about seven inches tall, performed a full 3db louder than its competitors. That is the same increase in loudness that you would get if you doubled your power, and is definitely noticeable to the listening stations.
THE TALL DUCKOften called the 5/8 duck, even though few are actually that long, the tall duck starts to perform like a real antenna should, giving gain to the signal instead of loss from an inefficient short length. In the case of the Smiley 5/8 Slim Duck, the antenna provides 6db gain over a competitive standard sized duck. Since this is the same as increasing your power by a factor of four, it is very noticeable to receiving station.
COMMON PRACTICEBefore long, when you have an assortment of ducks to use, as we have had here, you quickly sort them into the two categories that are truly important…. A very short duck for talking radio to radio around the homestead, and a long duck with good performance, for talking to the repeaters in the area.
That is exactly the combination that Smiley put together in their 5/8 Slim Duck Combo package available from them for $30.00 plus $6.50 shipping and handling.
In addition, you should note that they use a modular system, and that the antenna can be furnished with any of a multitude of connectors. Most radios today use BNC connector and so the standard package comes with one BNC connector and two antennas. If you are planning on changing the antennas very often you will want a second BNC connector, available at the same time you order the antenna for an additional $6.00.
Antennas can be tuned for almost any frequency you could desire, but for our use just ask for the two meter model and it will be tuned in the center of the band, which is ideal, for the tuning is very broad on the two meter and the antenna will easily cover the whole band.