Colonial radio

June 24, 2005 11:01 PM

Why is one station taking over all frequencies on my alarm clock radio?

I like to listen to the local campus radio station, which is 88.7FM. My large stereo picks it up as clear as a bell. In the next room, I have a small clock radio which seems to be having issues. Sometimes it can pick it up, but the signal is very weak-- this doesn't surprise me, because, well, the big one has an external antenna and the little clock radio does not.

What puzzles me more is that recently, when I've tried to get 88.7 on the clock radio, another station seems to cut in. It is another local station, which usually is found at 94.3. What's more, this phantom station seems to take up quite a fair bit of the dial-- I can pick it up from as low as the dial will go up to in the low 90s, and then, of course, its regular frequency.

This is a bit frustrating for me, as I don't like that 94.3 station much, and it is a bit disconcerting to be listening to the one station, dozing off, and then waking up to a completely different station, especially one that should be a good distance away on my dial.

What causes this? And, more significantly, how can I fix it? I've learned that I can get a stronger signal by putting headphones into the headphone jack (though not far enough in for the audio to go to the phones) but that doesn't seem to help with this.

BONUS QUESTION: Is there anyway to get some kind of proper antenna on this little radio that has no obvious place to put an external antenna?

posted by synecdoche to technology (9 comments total)

I'm not an expert in radio, but it just sounds like your radio is on its last legs. How long have you had it? It might be time to just get a new one.
posted by borkencode at 12:18 AM on June 25, 2005

Don't know about why that station is taking up so much bandwidth, but you've answered part of your own question, here:

I've learned that I can get a stronger signal by putting headphones into the headphone jack (though not far enough in for the audio to go to the phones) but that doesn't seem to help with this. Is there anyway to get some kind of proper antenna on this little radio that has no obvious place to put an external antenna?

You have discovered that cheap radios use the headphone cable as an antenna - connecting a long wire to a headphone jack and plugging it in half way, or, indeed, connecting an antenna to that part of the circuit inside the unit will allow you to add an external antenna.
posted by Jimbob at 12:28 AM on June 25, 2005

Is the transmitter for the 94.3 station close to your home? If so, its signal is probably so strong that it overwhelms the less-sophisticated tuner in the clock radio. The other radio has circuits to prevent that. ing an antenna to the clock may not help.
posted by Kirth Gerson at 2:47 AM on June 25, 2005

Adding an antenna
posted by Kirth Gerson at 2:48 AM on June 25, 2005

The radio is new-- I only bought it a month or two ago. The 94.3 transmitter is not terribly close, and the 88.7 transmitter (though, I am sure, significantly weaker) is much closer.
posted by synecdoche at 7:34 AM on June 25, 2005

What Kirth said; Your clock radio is suffering from blanketing interference. More sophisticated (i.e., more expensive) radios are less bothered by this sort of thing.

If you can, try returning it for a different model. There isn't a 100% correlation between selectivity and cost, so this might do the trick even if the other radio is in the same price range.

Back in the day, the manufacturers took this sort of thing more seriously, so older clock radios tend to be better about these things. You could try hitting Goodwill or the Salvation Army for a solid-looking, big-name pre-loved model.

If you are really attached to this radio, consider this: your problem is that the interfering signal is too strong, therefore weakening the signal might help. Here are some things to try:

1) Easiest -- try moving the radio around the room.

2) Many (most?) clock radios use the power cord as an antenna. Look underneath the radio -- sometimes there's a sliding flat metal piece bridging two screws. If it's there, unplug the radio, loosen the screws and slide that plate over to the open position. This will unhook the input stage from the power cord.

Note: the bridge should be obvious on the outside of the radio and look like it's intended to be messed with. If you need to do something more invasive, then your radio lacks that metal piece, which leads us to...

3) If you're comfortable with such things, you can open the radio up (while unplugged, of course!) and see if you can figure out where the input stage links into the antenna and cut/desolder the connection. Do this only as a last resort as it will be a pain in the neck to undo. You'll probably see a ferrite bar with coils of wire around it inside the radio -- this is the AM antenna and shouldn't have anything to do with your problem, so don't mess with any of its connections.

4) You could try using a more directional antenna (assuming you have the hooking an antenna up problem licked) to focus on the desired signal while minimizing the influence of the commercial station. Sometimes a piece of wire wrapped around the power cord insulation and dangling in just the right way is good enough. Be sure to keep any such wire well away from live electrical connections.

Personally, I'd probably try 1) and 2) first and spend about 5 minutes on 4) and if those didn't work replace the radio. Good Luck!
posted by Opposite George at 11:44 AM on June 25, 2005

A clarification: If you try the wrapping-the-dangling-wire-around-the-cord trick, make sure the sliding plate is bridging the screws again or you won't be doing anything.
posted by Opposite George at 11:50 AM on June 25, 2005

I had this exact same problem listening to my college station. It prevented me from picking my NPR station. It turned out that the engineer at the NPR station was also the station manager of the college station. I got this response to an e-mailed query:

Re: larger antenna — actually, since the wavelength at 89.1 is longer than at 90.7, you’re better off to pick up ‘VTF.

As for your AC-powered radios, there may sill be hope. A lot of those will couple with the power cord (a convenient 36?) to and use that as an antenna. I know that some of UVT’s signal gets into the power system (I’m assuming you’re on Tech Electric), and the synchronous AM rides in and takes over “every other station on the band”. Sometimes you can take some ferrite chokes available at Radio Shack and block out some of that AM. Give it a shot.

Make sure your aerial is away from electrical conduits/wire runs in walls. That also seems to help.

The optimum set-up I’ve found is to get a radio with an external antenna input and hook up a folded dipole to it. In your case, this should be done near a window facing north or east.

More on my blog.

synecdoche, are you on the same power grid as your local college? (Or, perhaps more important, does your local college generate their own electricity and are you on their grid?) And is your radio AC powered? If so, you might want to consider a battery-powered radio. It worked for me.
posted by waldo at 11:56 AM on June 25, 2005

Waldo, I think you may be right, except that I am on the 94.3 power grid, and not the unersity's (hence why I get them just about everywhere but not the university station). Wiggling the cord helps but as soon as I put it down it goes back to the station I don't like.

I don't really want to replace the radio. I know it is cheap and all, but I got it because it was the cheapest one I could find that could play CDs (which was a nice feature for me). Maybe I'll just have to make do-- thanks to this thread, and my poking around, it is clear that the power cord is serving as the antenna.
posted by synecdoche at 6:16 PM on June 25, 2005