How Do I Get Clear Signal out of My FM Transmitter for My Christmas Light Display?

When you’re making an animated Christmas light display, one key part is often the music. This allows you to make your light sync with the music you choose, and create a really impressive show!

While it would be really cool to set up a big PA system and blast your tunes through the neighborhood, your neighbors might not be excited about that approach!

That’s why we use FM transmitters to play our music over the radio so that cars driving by can hear our music and enjoy the show without bothering the neighbors!

The first step is to get the right FM transmitterand I cover that here in this article!

But even when you have the right transmitter, it’s not always easy to get a great signal – especially if the road or driveway is a distance away from the transmitter!

This is a big problem and the reason why pretty much every FM transmitter you can buy has bad reviews online! Getting a good transmitter is half the battle, but then you need to know…

How To Get Clear Signal Out of Your FM Transmitter

But then we need to place it well, optimize our audio, and optimize our radio broadcast.

When you optimize for these 3 variables, you’re MUCH more likely to get a clear broadcast of your display across anywhere that it can be seen.

Here’s what to do!

How to Place Your Transmitter Optimally

When you open up the instructions of most FM transmitters designed for the hobbyist, you will find some very vague instructions about where to mount your transmitter – if you get any instruction at all!

When I bought my first transmitter, I was faced with the same thing, and it didn’t really help me determine where to put my transmitter.

So, I started experimenting and exploring.

I moved the transmitter up high on the wall, I moved it low. I tried it just inside exterior walls, and also on interior walls. I moved the antenna around, and I tested the results.

By far, the biggest impact was made by getting the transmitter up high and as close to the front of the house as possible.

For me, this made the difference between barely being able to get a signal in my front yard vs. getting a signal in my car at the end of the street hundreds of feet away.

This makes sense if you understand or think about “real” full-power FM radio – they always get their transmitters up on hills or mountains, and then mount the antenna on a tower to get it even higher!

Anything solid between your transmitter and the audience will cause the signal to be weakened – including drywall, insulation, etc.

I did find, however, that it was better to get the transmitter high up inside my front room, vs close to the ground outside.

Metal objects reflect radio signals, so you should keep your transmitter clear of any metal sheeting, foil-backed insulation panels, etc. (Most home insulation is not foil-lined)

It seems that (for my house, at least), getting the transmitter up high was more important than getting it outside. But, mounting it on the front side of the front bedroom DID make a big impact vs the back side of that same bedroom, just 12 feet away.

Your results, of course, may vary.

How to Optimize Your Audio

Once you’ve got your transmitter mounted in the right place, it’s time to get the audio right.

Audio professionals often talk about “signal vs noise”, and this applies so much when working with an FM transmitter.

If the audio you feed into your FM transmitter is too low, you’ll hear a lot of static because there is always some static in the background, and you have to turn the sound up a TON to get your music feed. The amount of signal vs the noise that exists in your system is too close in volume, and it becomes difficult to tell the two apart!

But, if the audio is too high it will “clip” which also causes distortion and static.

You want your music to be at a consistent level between songs (or “normalized” which can be done with a program like Audacity), and you want that overall level to be as loud as possible without causing any clipping.

normalize audio audacity
Use programs like Audacity to normalize your tracks

Normalizing is an important first step, since music tracks from different decades, styles of music, or different media (i.e. ripped from CD vs bought online) will be at different levels!

Once the audio is normalized, you can find the best level to run your show at.

The best way to find this level is to start low and keep bringing up your volume until you begin to hear distortion or clipping on louder portions.

Then, back it off a bit and you’ve found the perfect volume!

It also helps to get a good quality audio interface from your PC. There are many great options that use USB audio to get a much clearer signal from a PC or Raspberry Pi, such as:

…and neither of these bust the bank account!

How to Optimize Your Broadcast

Last, we need to make sure we are broadcasting at the right frequency and power.

Because we are transmitting at much lower power than licensed radio stations, we need to stay out of their way if we want to have a chance at being heard!

Thankfully, the free website “https://radio-locator.com/” allows you to enter your location and see what the best open radio stations are.

Radio-Locator Website Results

Often, these are at the bottom of the FM band (such as 87.9), but that isn’t always the case. If you in a major metropolitan area, it might be difficult and take some trial-and-error to get the best frequency picked out.

You also want to consider other displays. If other people are broadcasting a Christmas light display in your neighborhood or nearby, check to see what frequency they are using and use something different!

Make Your Clearest Audio Ever

I truly hope that this article has helped you make the clearest audio possible for your display.

While getting your radio transmitter set up correctly might seem like “magic” it doesn’t have to be mystical! Follow these steps and you’ll be on your way to your clearest audio yet!

About the author

David Henry

David first began using pixels in stage lighting, and then decided to try it out on his house. The result? An urge to create useful and helpful information to help non-technical folks create great Christmas lighting with pixels on their homes!


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