Why are some antennas hollow?

Most outdoor antennas are made from extruded aluminum or rolled aluminum. Either way, they have an outer metal shell and are hollow inside. For some people this seems like they are being cheated — after all who among us wants to bite into a hollow chocolate bunny when we were expecting a solid one? So naturally it seems like you’re not getting the full value when you get an antenna that’s mostly air inside. That makes sense if you think about it…

…except it’s not true.

Antennas are hollow for two reasons:

Keeping them hollow makes them light and they’re still strong enough.
Antennas are strong enough to support the occasional bird or flying twig. They don’t need to be stronger than that. A solid antenna would be stronger and could potentially absorb the impact of any number of improbably flying objects, be they cows or wicked witches or what have you. But in the real world a hollow antenna is strong enough.

Adding metal does add weight, and that means a solid antenna would cost more to ship (and you’d pay more to ship it), it would cost more to make because of the extra material, and you’d need stronger support posts to mount it. A stronger antenna could also potentially damage your roof if it falls; one thing about a hollow antenna is it’s not likely to go through the roof even if it snaps off.

Only the outside of the antenna matters anyway.
An antenna’s ability to pick up signals is based on how much of it actually faces the signal. That’s why some of our antennas are stamped out of flat metal. They don’t need to be any thicker, but the extra surface area helps them get signal. It’s also why our flat indoor antennas work as well as old-school ones, because even a layer of silver a few millimeters thick works just fine. Adding solid metal doesn’t make it work any better.

When you look at things that way, you’ll see why hollow antennas make sense. They’re less expensive to make, less expensive to ship, less prone to damage the roof, and work just as well. Now, as far as those hollow chocolate bunnies… that’s just got to stop.

About the Author

Stuart Sweet
Stuart Sweet is the editor-in-chief of The Solid Signal Blog and a "master plumber" at Signal Group, LLC. He is the author of over 8,000 articles and longform tutorials including many posted here. Reach him by clicking on "Contact the Editor" at the bottom of this page.