On Computers

Listen to On Computers on Your FM Radio

24 August 2003

Gail Allinson, gail@oncomputers.info

No, we haven't made some great broadcast deal (yet).  And no, you won't be able to listen to the show while you are driving down the highway, but you will be able to listen to the show just about anywhere in your house or in your garden.

Before I go on here, I need to make an important disclaimer. What I'm about to discuss may not work from a legal standpoint in all parts of the world.  In the US there are provisions to transmit a radio signal under some limited conditions on the regular FM radio band.  I'm not going to bore everyone with the details, but if you need or want to know the details you can find them here. Check the regulations in your country before using an RF (radio frequency) transmitter. I don't want any of our listeners unwittingly landing in the hoosegow.

So if you haven't already figured it out, what I'm going to do is to tell you how to attach a small FM radio transmitter to your computer. First you do need a sound card (or a motherboard with integrated sound) in your computer.  Your sound device needs to have an audio out jack.  It doesn't need to be anything fancy, just the typical analog audio jack-- the same one that you use to plug in your front, or your only, analog audio speakers.  In most newer computers, this jack is color-coded lime green.

So far so good. You have located the audio jack on your computer.  Now what?  Well second, you need to get a small radio transmitter.  I bought one at my local Radio Shack store, but there are others available from other vendors.  Typically these transmitters are advertised as something you can plug into your CD or MP3 player to listen to the output on the FM radio in your car or house.  What you may not have known is this same transmitter works quite nicely to send the sound from your computer to your FM radio.  The smaller, less expensive transmitters are usually battery operated, transmit distances of 30 to 100 feet more or less, and have a small range of frequencies that you can choose from.  The one I have has 4 frequencies which correspond to frequencies that I can tune in on my FM radio. Which frequency you will actually choose to use depends on the one with the least interference from FM stations in the area.  Choose an unused frequency, or the frequency with the weakest station.  Where I live, because I live at a relatively high elevation (it's like having a really tall antenna), the best I can do is to choose the weakest station.  That is still good enough because, at  the short distance between my transmitter and receiver, my little signal is still comes in stronger than a distant station.

One suggestion I have is that when you are initially setting up your transmitter, you may just want to play an .ogg or .mp3 file that is stored locall rather than streaming audio, which is more subject to the vagaries of the Internet.  First, make sure your audio is working over your speakers.  To be really safe, shut down your speakers and your computer.  Next unplug your speakers and plug in your transmitter. You may want to use an extension so that you don't have the transmitter sitting on the floor or dangling from the back of your computer.  Also for testing purposes,  have your FM radio tuned in to the right frequency and make sure the volume is turned up.  If you don't, you will have no way of hearing if you are successful.  Turn your computer on, start playing your music, turn on the transmitter, and see if you can hear your music on your radio.  If you can, you have succeeded.  If not, check the connections, the frequencies, make sure everything thing is on, and that the volume is turned up enough for you to hear.

If you have an FM Stereo radio, and an FM stereo transmitter and a stereo file, you will hear stereo. But if any one of the above is mono, you will hear mono.  Typically these little transmitters are stereo because they are primarily designed to transmit stereo music.  Note that I've said nothing about software. That's because you can use any software that you normally use to play your music files on your computer.  It doesn't matter which software -- just use your favorite of the one associated with that file type.

FM Transmitter, Switch, and FM Radio

Once you have tested the system, it is time to try it with streaming audio.  Of course the first thing you'll want to listen to is the On Computers Internet only radio show at http://oncomputers.info.

One very nice thing about having a transmitter is that you can go get coffee in the next room, or even water the flowers outside and not miss a moment of the show.  A small portable radio (like a Walkman) with earphones is perfect for gardening, by the way. And if you are really a diehard fan, remember, you can get even get a waterproof, battery operated radio for your shower.

This is all well and good, but it really is kind of painful to have to crawl around unplugging the speakers and plugging in the transmitter.  Again the local Radio Shack comes to the rescue with a very nifty little switch that was designed to allow me to switch from speakers to headphones at the touch of a button.  You may not need a switch if you have a headphone jack on your speakers -- you can probably use that.  Generally, anything that you can plug your headphones into, can be used for your transmitter because that's what it was designed for -- to plug into the headphone jack of an MP3 player or a CD player.

Also remember, the audio you hear will be, at best, only as good as the audio on your computer.  For example, I listen on the On Computers snail feed because I only have a dial-up connection.  Guess what?  Even though I'm transmitting stereo, I'm only hearing mono because that is what the stream is.  Also, it sounds like an am radio, not because I'm using the AM band, but because at that low bandwidth, that's as good as the sound gets.

Here are some examples of transmitters:

irock! 300W - FM Transmitter

Belkin TuneCast Mobile FM Transmitter

C Crane Digital FM Transmitter

MP3 Hi-Fi Stereo FM Transmitter

For the more adventurous, transmitter kits:

HI-FI Stereo FM Transmitter - CK222

Ramsey Electronics FM10A

Station Guide (so you can pick the best frequency to use in your area and also find streaming audio to listen to)


Radio Shack Switch

Computer Headphone Speaker Switch


© 2003 Gail Allinson

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