VHF – UHF Antennas — Which Antenna Is Best For My Location

If you are a dedicated on the go hand held walkie talkie user this information is probably not very useful to you.

My intention is to help new/novice radio users make wise choices and get the most benefit from their radio investment.

The 3 most common antennas are (1) 1/2 wave Dipole, (2) Vertical and (3) Yagi.

Yagi antennas are multi element (beam) antennas and are highly directional and can be vertical or horizontal polarized depending on how they are mounted. Unless you are setting up a point to point communications link Yagi is probably not a good choice for your primary antenna system.

1/2 wave Dipole antennas have 2 diametrically opposed elements, with each element being 1/4 wave in length. Dipole antennas can be mounted vertical or horizontal. Horizontal dipoles are bi-directional while vertical dipoles are more omnidirectional. A vertical mounted 1/2 wave dipole has very near the same characteristics of a 1/2 wave vertical antenna.

Vertical antennas are commonly 1/4, 1/2 or 5/8 waves in length. With few exceptions, to work properly a vertical antenna commonly has 2 or 3 – 1/4 wave length ground plain radicals located at the base of the antenna. When vehicle mounted, the vehicles steel body/frame acts at the antennas ground plain.
If you are wondering why your HT/Walkie Talkie has no ground plain radials, it’s because your radio’s metal frame work is acting as a very poor ground plain for your inefficient antenna.

Antenna current distribution based on antenna wave length.

Antennas longer than 1/2 wavelength show more current at the base that is out of phase with that in the upper section of the antenna. That’s what contributes to decreased low(ground) angle of RF radiation.
The 5/8 wave antenna has more conductor that is radiating but 1/8 wave of that radiation is out of phase with the main radiation, so it actually reduces the radiation at the horizon. An explanation for this is that the out of phase portion at the base has low enough current that it doesn’t have a significant effect on the over all radiation pattern. Ignore it and that leaves us with the same current distribution as the 1/2 wave vertical, just a bit higher on the horizon.

Which antenna works best if the top tip of antennas are at the same height.

Conclusion: 1/4 wave ground plane with sloping radials, 1/2 wave dipole, and 5/8 wave vertical with the tops at the same height over perfect ground. Performance is virtually identical for all three antennas.

You can’t change the fact that VHF/UHF frequencies are line of site. You can increase your line of site by increasing your antenna height. Mount an antenna on a pole tower tree. Move to a near by high spot/hill top.
Line of site calculator: https://www.southwestantennas.com/calculator/line-of-sight

Antennas are only as efferent as the amount of RF energy reaching the antenna feed point.
Antenna mismatch (SWR – Standing Wave Ratio) and Coax dB loss are big factors in your antennas real transmitted RF power. A SWR of 3:1 = a loss of 50% of your transmitters output power at the antenna feed point.

An antenna is only resonant on one frequency, as you move up/down in frequency you introduce increasing antenna miss match and loss of transmitted RF power.
To calculate your antennas resonant frequency: 234 divided by operating frequency time 12. Example: 1/4 wave antenna, 234/FX12 will give you antenna length in inches. Example: 1/4 wave antenna 234/462.550 MHzX12 = 6.070 (6 1/16) inch antenna. To calculate a 1/2 wave antenna 468/462.55X12 = 12.141 (12 9/64) inches.

Coax Loss: Coax is a contributor to the amount of RF power reaching your antennas input connector.
Coax Attenuation Chart: Measures the attenuation (loss) of different types of coax at 50 foot lengths.
Attenuation is measured in dB.

Your antennas claimed gain will be reduced by the amount of coax loss. A claim of 4 dB antenna gain will be deduced to 0(zero) gain using 50 feet of RG8X coax feed line.

J-Pole is one of the exceptions I spoke of, an antenna not requiring ground plain radials. Easy, cheap to build and works as well as any $150 dollar commercial made 1/2 wave base antenna. There are many DIY J-Pole projects to be found on line. A easy J-pole calculator can be found at: https://www.hamuniverse.com/jpole.html

I hope this information is useful to you in your efforts to design and install a functional radio communications system.