Call this one confirmed. Roof-mounted air conditioners can absolutely affect the performance of cellular signal boosters. It’s a big enough problem that at least one manufacturer recommends considering the location of the AC unit when installing a booster. Let’s take a look.
It’s all about noise.
Let’s be honest here. Noise is a big problem for all forms of digital broadcasting. This includes cellular boosters, because cell phones are all digital and have been for 20 years. When you’re trying to receive a digital signal, you’re getting ones and zeroes. If you can tell the difference between a one and a zero, it doesn’t matter how strong the signal is. All that matters are the ones and the zeroes. That’s why I’ve called signal-to-noise ratio the most important measure of over-the-air signals. You can add more signal by placing an antenna up above most obstructions like trees. However, you have to be careful to avoid things that make noise.
Air conditioners make noise?
Yes they do. In fact practically every piece of electronic equipment generates radio-frequency interference. It can’t be too much because the FCC wouldn’t let them build something incredibly noisy. However, that rule really only applies to things that have been manufactured, at the time they’ve been manufactured. It doesn’t apply to something that has been sitting on a roof for 20 years. The shielding that might have stopped stray RF radiation in the past might be broken, or the AC unit might be generating unexpected amounts of signal due to parts wearing out.
Mind the AC units on the roof.
When you’re looking for a place to put an outdoor cellular antenna. You might want to take signal readings from several locations, one near the AC unit and one further away, to try to determine if the AC unit is causing interference. You might also realize that the AC unit itself is physically blocking the signal and you might need to put the outdoor antenna a little higher up in order to avoid it. Remember at its heart an air conditioner is a big hunk of metal and big hunks of metal tend to block signals.
Best option for installation: a good signal meter
If you’re serious about installing cellular signal boosters, you’ll need a good cellular signal meter. If you’re installing one for yourself, an Android phone is a great tool, since it can run a number of signal-meter-like apps. However, if you’re putting up boosters for a living, a meter is an indispensible part of your repertoire. It will tell you which bands are being received and give you all the information you need in order to properly place an antenna. Luckily, they’re also fairly inexpensive and worth every penny to the professional installer.