Why the Height of a VHF Radio Antenna Matters

If you spend any amount of time getting into amateur radio, there’s no doubt you’ve already seen how important antenna selection and setup are for success. The best radio in the world is no good without a good antenna, and even the best antenna can be hampered severely by improper placement.

Baofeng UV 5R5 HAM radio
a Baofeng UV 5R5 HAM radio

But particularly when it comes to VHF radio, for any purpose, antenna height is extremely important. But why is that? Why does the height of a VHF radio antenna matter so much?

The height of a VHF radio antenna matters because VHF signals are easily blocked or disrupted by obstacles. Making sure your antenna is high enough will help get your signal out over those obstacles and let you receive clear, static-free signals from farther away. It really is that simple…

It’s always a good idea to get your radio antenna as high as possible, but if you are transmitting or receiving VHF signals, be they audio or visual, you’ve got to get it up there so you can reach past any intervening obstacles like buildings, trees, or mountain ranges.

There’s a lot more you’ll want to know, naturally, so keep reading and I’ll tell you all about it.

VHF Radio is Highly Dependent on Line of Sight

VHF radio signals, be they from a ham radio, aircraft, marine radio, handy-talky, or anything else are generally considered line-of-sight signals. This frequency range, anywhere from 30 to 300 MHz, can easily travel several dozen miles in good conditions but it travels in a straight line and does not go around obstacles.

Because of this, they’re said to propagate based on line-of-sight, which is actually determined by the radio horizon, not visual horizon. That gets into a more complicated part of radio theory, and something we don’t have to discuss here for you to understand the practical problem.

In short, the higher your VHF antenna is, the farther away the horizon becomes, and the more capable the antenna will be when transmitting or receiving.

Obstacles Will Seriously Degrade or Block VHF Signals

As mentioned, obstacles and VHF signals just don’t get along, and the obstacles will always win.

Trees, neighboring buildings, hills, and anything else you can think of will easily degrade VHF signals if there’s not a repeater to help pass them along, or if the sending station is not already at the highest point out to the horizon.

You can easily see this for yourself in your own home, or with your handheld radio, if you’re trying to transmit or receive in a valley, next to a woodline, or in a built-up area with tall buildings around you.

Since we can’t get rid of most obstacles for one reason or another, our only option is to reposition the antenna for better line of sight or raise it to get past the obstacles.

How High Should Your VHF Antenna Be?

The rule of thumb is to place it as high as you can. Broadly, anywhere from 15 to 70 feet off the ground.

Usually, higher is always better when it comes to reception in the presence of obstacles and transmission of the same. This is especially important when you are transmitting or receiving on the upper end of the VHF range.

However, you must check your local municipal, county, state, and relevant federal regulations when it comes to antenna height!

You might be restricted for the overall height of the antenna itself, or the maximum allowable height for installation depending on zoning and a host of other factors.

It will be heartbreaking to get your antenna set up and dialed in only to get an order from officials telling you to tear it down!

Is Higher Always Better for an Antenna?

Generally, yes, but not always. It’s possible that getting your VHF antenna up there, really up there, will introduce more interference because it will be capable of picking up staticky signals from farther away that are dissipating, increasing noise.

In these cases, lowering the antenna is a good idea as it’ll cut down on unwanted reception. This assumes, naturally, that you can still clearly send and receive.

Keep this in mind because you might be better off with a shorter antenna that is on a higher mast, mount or other installation location. Especially if it’s easily adjustable or configurable, this might give you better overall control for dialing in the sweet spot for placement.

In any case, do not hesitate at all to experiment with raising or lowering your antenna, and moving it to a different location.

And do this incrementally, because a change of just a few inches might have a surprisingly big impact. Ideally, you won’t have any obstacles at all near it for at least a 5-feet radius.

Other Things You Can Do to Improve VHF Reception and Transmission

VHF antenna height is still only a piece of the puzzle when it comes to optimizing reception and transmission.

Depending on your circumstances and objectives, using a directional antenna can make a huge difference as long as you know how and where to aim it. VHF amplifiers and preamplifiers will allow you to boost transmission power and improve reception respectively.

Other good options for increased performance are reflectors which can bounce your signal off of or over obstacles, or help to maximize your reception when you are at the very limit of what your set can do.

Lastly, don’t forget that a repeater is a viable, but often pricey, option for extending range in both directions. Expect to spend at least a couple hundred dollars for most applications, and it might cost upwards of $2,000!

If all else fails, consider upgrading your antenna. Aluminum antennas are okay, but you’ll invariably get better overall performance from copper or brass. Start by trying to get the correct height dialed in, and if that fails, look into the options listed above.

Leave a Comment

Your email address will not be published. Required fields are marked *