Is there a perfect antenna? As radio amateurs, we often ask ourselves such a question, but also often be troubled by the choice of antenna, today the author of this article Onno VK6FLAB to talk to you!
<h1 class="pgc-h-arrow-right" data-track="3" > inherent redundancy of compromise antennas</h1>
Text: Onno VK6FLAB
For an activity that permeates the art of communication, radio amateurs are a diverse group of people who share common interests and use imperfect language to describe an inherently complex science, hoping that we can learn from each other to connect and make our own voices heard.
Language is important in this collaborative effort.
Let me start with Arthur Frackenpohl's oil poem:
There was a lad in Perth who was married on the day he was born, and they said he died on his wife's wedding day when he left Earth
There was a young fellow of Perth Who was born on the day of his birth He married, they say On his wife's wedding day And died when he quitted the earth
Talk to me about this.
In this day and age, first of all, let me give you a short summary, pieced together from a new invention, conceived as you watch the evening sunset close to the beach.
What this tautistic cornucopia has to do with our hobbies may not be obvious, but let me illustrate.
Think of the phrase "compromise antenna" and "Oh, I'll never use that antenna, it's a compromise antenna." ”
If you've been in the amateur radio community for a while, you've heard this phrase, and unless someone points it out, you probably don't realize that it's not helpful in nature.
<h1 class="pgc-h-arrow-right" data-track="57" > Why? </h1>
Because as I've said many times before, by definition, all antennas are a compromise. This is true on several levels.
Fundamentally, an isotropic antenna is an antenna that theoretically radiates equally in all directions, with the same intensity in both horizontal and vertical directions. It is infinitely small and can run on all frequencies with unlimited bandwidth. Ideals are full, reality is bone, in fact this kind of antenna is not physically present, so each built-in antenna represents a set of trade-offs or compromises, and no antenna can radiate more total power than an isotropic antenna.
Beyond that, within the physical limits of antenna construction, there are more compromises. This may not be obvious now, so let me elaborate.
Consider a 28 MHz, seven-unit Yagi antenna. It features a boom of 12m, a reflector element of 5.3m, a turning radius of 7.5m and a weight of 53 kg. At 20m off ground, it has a gain of 17.5 dBi and a processing power of 1.5 kW. It is physically capable of withstanding wind speeds of 180 km/h. It's a cute kit that is definitely a gift you might want to receive on your birthday if you have enough space, and it can be fixed to a mast somewhere near the station.
If all antennas were compromises, you might be asking yourself, how does this beautiful 10m Yagi compromise?
First, its total radiated power is less than that of an isotropic antenna. It operates between 28 and 29 MHz, but not elsewhere. It radiates signals very well in one direction, but not in any other direction. It requires a lot of open space, and as a fixture it had to be mounted on a heavy-duty rotator clamped to a high mast. The actual purchase and installation required more money than I have spent on all radio stations so far.
Some of the content I mentioned may be acceptable to you, and some are not. For example, if you always carry it with you, this antenna doesn't make sense. By making your choice to choose the antenna that works best, you are introducing a compromise.
In addition, some amateurs will convince you that an eclectic antenna is a high-loss antenna.
<h1 class="pgc-h-arrow-right" data-track="58" > what does high loss compare to? </h1>
If you live in an apartment building, you can't install 10m yakugi in your bedroom, so you can compromise and switch to a magnetic loop antenna. If you are at the top of the mountain, there is no chance to erect the structure, so you can use a self-supporting vertical structure. If you're in the car, you can't put up a horizontal dipole and drive along the highway, so you put a whip antenna in your vintage car.
All the choices you make to fit your purpose, environment, budget, and available materials will be combined into one antenna that hopefully will allow you to make a sound in the air.
When someone tells you that an antenna is a compromise antenna, what they're really saying is that you've made a compromise that they wouldn't have wanted to make. If you have unlimited space, money, experience, and opportunities, it's easy to say. In other words, they're just bragging.
The whole point of antenna construction is to find a specific set of trade-offs that fit your situation at the time. The aim of this hobby is to understand what the effect of a particular choice is and how it affects the operation of the antenna in a particular situation.
The next time you hear the superfluous phrase "This is a compromise antenna," ask them what they describe as unacceptable compromises and decide for yourself whether they are compatible with what you're trying to achieve within the range of available resources.