What is the "Best" Antenna?

Anytime I hear the word "Best" in a question I'm afraid I cringe a little. The problem is that what is best for one person or best in one set of circumstances is not best for another person or circumstance.

So let's try something different. What criteria should we use to select an antenna?

First of all, no sense looking at antennas that aren't for the frequency you are interested in. Is it going to be HF orVHF/UHF?

For either category, the next step will be a decision about Polarization. Mostly it will have to do with either Horizontal or Vertical polarization. Horizontal means that the radiating elements are mounted parallel to the surface of the earth and in vertical polarization the antenna elements are mounted perpendicular to the earths surface. From a performance standpoint, polarization is very critical in line of sight communications. There is a 20db or more loss of power when two stations are not on the same polarization. Actually this only applies to line-of-sight communications. If you are using F2 or similar propagation however, there is not as drastic a difference.

On HF the differences have more to do with "Angle of Radiation". You can see that a low angle of radiation from the antenna on the right will reach a greater distance than the high angle antenna on the left.

So what does this mean to the antenna buyer? For one thing, a vertically polarized antenna has a lower angle of radiation. Unless a horizontally polarized antenna is mounted more than a 1/2 wave above ground on it's lowest frequency, the angle of radiation will be higher than a vertical. Also in favor of a vertical is a space consideration. A vertical will take up only a few square feet of real estate but a horizontal antenna like a dipole will use up a lot of space.

Why is a horizontal antenna so popular? Also lots of reasons. They can be put up very inexpensively. A horizontal antenna is less susceptable to man made noise. A dipole can go into the air for $25.00 or less. Most verticals start at $100.00.

OK, so what about "Beams"? Well a directional antenna is great. Not only do you radiate your signal in primarily one direction which focuses the transmitter power, but because of the way a "Beam" or "Yagi" is constructed, it also allows you the ability to notch out or drop the signal level of someone that is behind you with reference to the signal you are trying to hear. That is referred to as "Front to Back". Not only will an antenna have a forward Gain of 6 db or more, but it will also knock down signals off the back of the antenna 20db or more.

Why doesn't everyone have one? They are a bit more expensive, they have to be mounted in the air at least a half wave in the air to have a low angle of radiation and they should have a rotator to be truly useful..

On VHF, things get a little less complicated. Only a little though. If you operate FM on the VHF frequencies, the rule of thumb is you should be using vertical polarization. If you are using SSB or CW and doing small signal work, you will get the greatest benefit using horizontal.

So, that should clear some of that up.

So now, let's talk gain. What does 6db gain really mean? If you were talking to someone and both of you were using zero gain antennas, and you doubled your power from let's say 50 watts to 100 watts, you would show an increase of 3db on his receive meter. If you again doubled your power from 100 to 200 watts, you would show again a 3db increase in signal strength on his receive meter. To show an increase of another 3db, you would have to raise your power from 200 to 400 watts.

Gain is also derived from antennas. A 6db gain antenna is the same as doubling your power twice from 50 watts to 200 watts. With one addition. The station on the other side of the conversation also benefits from this. When he transmits, his signal is going to be 6db higher into your receiver also. This is very inexpensive power. Now if both of the stations had 6db gain antennas.............Wow!

If you have a station you want to reduce the signal strength from, you can put him with the back of the beam pointing at him which will decrease his signal strength 20-25 db. Assume his station is 100 watts and then divide it in half 7 times. (3db goes into 21db front to back 7 times.) There is not much left, is there. He probably won't bother you much with an apparent power level of 1 watt.

Yagis are really exciting antennas and they have a lot of benefits. However, there is a downside as it more expensive to put up a directional antenna than a dipole or vertical.. Consider the cost of a mounting structure such as tower. Then, there is no point in having a directional antenna if you can't point it at someone. At will. So you are also looking at the cost of a rotator system and associated cables.

So which is the BEST antenna? It's a very good question with a lot of answers. A rule of thumb for antennas: Higher is better than lower and larger is better than smaller. You won't go wrong with those two rules.

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