Choosing the right Omni

Finding the right Omnidirectional Antenna: Key Takeaways

When looking for the right omnidirectional antenna for your application, there are a few key questions that you want to consider.

Is the antenna for receive only?
If transmitting, does it need to account for low, moderate, or high levels of power?
What platform will the antenna mount to?
Handheld, manpack, vehicle, portable and fixed site, all the way to naval, and spacecraft.
What’s the frequency of operation?
For transmit, what’s the maximum continuous power the transmitter will output? And what maximum VSWR can the transmitter tolerate?
What gain and radiation characteristics are required? Relatedly, is a ground-plane dependent or independent omnidirectional antenna desired?

To find the optimal antenna, exploring these questions will put you on the right track!

Video Transcript

The following transcript has been lightly edited for clarity and readability.

So, say you want an omnidirectional antenna for tactical communications. What does that really mean? Or maybe, more generally, you think you need an omnidirectional antenna. How do you go about choosing it?

The answer isn't that easy because there are a lot of different potential operational scenarios.

The first question you might ask is: Is the antenna for receive-only, or is it for transmitting? If it's transmitting, will it operate at low, moderate, or high levels of power? All of these things will influence the kind of antenna you choose.

The second consideration is: What platform will the antenna go on?

There are antennas for handheld radios, manpack radios, vehicle radios, tactical portable situations, and also fixed sites. There are also omnidirectional antennas that go on naval, airborne, and spacecraft platforms.

So, it's not a simple question to answer: "What's the best omni antenna?" You first need to understand where it's going to go.

For number three, the question would be: What frequency does it need to work over?

That could range anywhere from HF, with frequencies in the single to tens of megahertz, all the way up to gigahertz-level frequencies. Those requirements will definitely influence the choice of an omnidirectional antenna.

If you're transmitting, you also have to consider how much power the transmitter will put through the antenna and make sure you've chosen an antenna appropriately rated for the amount of power it may see.

Related to that is how well the antenna is matched, or its voltage standing wave ratio (VSWR). If VSWR is too high, the amplifier can be damaged, so that's something you need to take into account when considering the radio alongside the choice of antenna.

Finally, another important consideration is: What kind of gain and radiation characteristics are required from the antenna?

The gain number is basically a measure of sensitivity—how well the antenna can translate electrical currents into radiating fields, or vice versa.

Radiation characteristics, or directivity, are also important. With an omnidirectional antenna, you basically have an antenna that radiates similarly in all directions around the antenna.

There are two different types of antennas that are generally used as omnis: dipole antennas and monopole antennas.

Dipoles are very versatile and can be used pretty much anywhere, but monopole antennas require a ground plane, or so-called counterpoise, in order for them to work. The characteristics of that ground plane are important in terms of how well the antenna will radiate.

All of these considerations come into play when choosing an omnidirectional antenna.

If the desire is to have the optimal antenna for a particular situation, you really have to explore all the different aspects of how that antenna is intended to be used and what kind of concept of operations it is intended to support.

Of course, if you have questions along these lines or want to find out more, you can give me a call or chat with me online. We can go through the whole list of parameters and come up with the right solution.