That was the question posed by one of our customers. That’s just what they wanted to do… and for some reason it wasn’t working. I thought this would be a great blog article, so I set to looking into it.
Why this wouldn’t work
Some antennas have something in them called an FM trap. An FM trap blocks FM signals on a TV antenna. This is sometimes necessary because strong FM signals can cause interference if TV signals are a lot weaker. But, it’s not common. So, FM traps aren’t installed on most antennas and it’s actually hard to get hardware with an FM trap.
But, I had to know.
What I did
I put a Winegard Metrostar antenna on the test bench and powered it up. I checked that I was getting live TV, because if the antenna wasn’t able to do that, I figured I needed to move it outside. Luckily I had no problem getting live TV.
I then used my trusty Televes H45 Spectrum Analyzer — the same one I use for all antenna tests — and set it to read the FM spectrum from 88-108MHz. Here’s what I saw. The H45 doesn’t have a screen capture button, so this is a cell phone pic of the screen. Sorry for the low quality.
There’s a lot of information on the screen but really you don’t need all of it. What you do need to know is that if there were an FM trap built in, the area near that dashed yellow line would be really low and flat. Kind of like it is just to the right of the yellow line. But, the presence of the high, spiky signals just to the left of the yellow line says that it’s picking up FM signals. IT’s very obvious. Not only that, you can see how the FM signals are really strong, stronger than most of the other signals around them.
In my test area, there isn’t any real strong broadcast from 103-108, but there is a strong transmitter at 95.1 and 99.9, and that’s just what I’m seeing here.
In other words, there’s no question that this antenna picks up FM.
How to use a TV antenna for FM
It’s incredibly easy. Pick a super-cheap splitter, pretty much any one will do. Run one side to the TV and one side to the FM receiver.
At this point you’ll have to do some work depending on how the antenna is connected. If it’s a monopole antenna, you could connect the copper center conductor to the end of the antenna. If there’s a bare-wire connector, use a balun like this one to turn it into two bare wires. (Just stripping down the coax cable and connecting it that way doesn’t work as well.)
Once you’re fully connected, you’ll be enjoying great quality FM signals!