I bought a cheap boombox to listen to the radio while at work, but I work on the ground floor of an office building that is chock full of interference causing materials and technology. The end result is that I pick up 1 AM station and 1 FM station… most of the time. And neither station is one that I want to listen to. I’m smack in the middle of Kansas City and should be able to pick up dozens of stations.
Is there an easy way that I can bump up the reception on my POS boombox? It has a typical collapsable mast antenna, and no input for an external antenna. Perhaps soldering wire to the mast antenna and then wrapping it around mast? Cutting off the mast antenna and hardwiring a powered antenna?
Soldering a long wire to the antenna might work, but it might overload the input stage of the radio (this is unlikely to cause any permanent damage - try it out by just wrapping the bare end of the wire around the antenna, before soldering.
Sometimes it works better if a long wire is not directly connected, but just near to the antenna. I got good results in a similar situation to the one you describe by taking the end of the long wire, and wrapping a few turns round a paper tube, and sliding that over the antenna. The paper tube was about half-an-inch in diameter, and I experimented with different numbers of turns till I got the best reception (which happened at about ten turns).
Can you get bad receptions for the stations you want? If you do, try turning the radio to mono instead of stereo, I find this makes the reception better.
I wish I could pick up internet radio. Our stupid IT department has removed the sound cards from all of our workstations. This was my fault, because originally, they just didn’t give anyone AC-adapters for the speakers built into our monitors. I went to Radio Shack and bought a generic one… and that was the day I learned not to screw with the IT department. Much gnashing of teeth that day.
I do get crappy reception on the few stations that I can make out but not completely bring in; but the radio switches from mono to stereo automatically.
The funny thing is that I suddenly get great reception if I touch the antenna or sit closer to the radio. I don’t know if I’m acting as a giant conducter (being that I’m about 200 lbs of salt water), or if I’m just reflecting more signal back to the antenna. If I grab the antenna, I pick up just about any station that i want… unfortunately, I need both of my hands to type or the problem would be solved.
One more time. You cannot improve AM reception by fiddling around with the antenna unless you go to a real fancy setup that will give some directivity in the direction of the station or stations you want to receive.
The reason for this is that, one more time, most of the noise at the AM frequencies is atmospheric noise or electrical interference from cars, lights, machinery etc. Such interference enters the receiver via the antenna. So if you lengthen the antenna, all you do is increase, maybe, both station signal power and noise power.
As to the FM, you are probably shielded from most of the stations by your building and other buildings in the vicinity. But that’s just a WAG.
Radio Shack sells a little long wire antenna on a reel that’s pretty neat. It has a conductive alligator clip for the radio’s antenna. You clip it on, then unreel the long wire. The reel even has a little rope loop that you can use to hang the long wire up on a hook, a doorknob, or whatever you want. It works surprisingly well.
Bear in mind that with a better antenna you’ll not just pick up more stations, but the noise around them. So if the receiver isn’t very good, you may hear more stations, but interspersed with lots of static.
Your best bet for AM is a loop antenna and most commercial radios, except the pocket sized, use a ferrite rod type of loop antenna. These are directional with the greatest sensitivity being at right angles to the long dimension of the rod which is usually also the long dimension of the radio cabinet.
So tune to a station and then try turning your receiver various directions when trying to receive AM and see if reception of that station improves.
As to wire antennas for AM. Any length of wire that is short compared to a wavelength is called a “doublet” antenna. The wavelength for the top of the AM band is about 200 meters or roughly 650 ft. So if the wire is shorter than 100 ft. or so the length really doesn’t make any difference as far as the ability of the wire to abstract energy from the radio field is concerned.
The ability of an antenna to abstract energy from the field can be measured by a quantity called the capture area. This parameter is equal to:
A = GL[sup]2[/sup]/4pi,
G is the directional gain relative to an isotropic antenna, or one that receives equally from all directions. L is the wavelength.
Radio Engineering by F.E. Terman gives the directional gain of any doublet as 1.5 and this is true for all lengths. So the parameter that tells us how much energy is abstracted is constant at any given wavelength for all long wire antennas that are short compared to a wavelength.
So, try a ferrite rod antenna and that’s as good as she gets.
The best AM radio I ever had was a tabletop Zenith made in 1952. It had a wire loop antenna stuck on the back panel. I could pick up WABC in New York without much trouble, and stations from Burlington, etc (I’m in coastal Maine). I eventually sold it. Drat.
So why are the newer radios unable to do this? Are the designs just that cheap?
Yep: cheap, cheaper, and cheapest. Back in the 50s, people routinely listened to radio stations a thousand miles away. I used to pick up stations 2000 miles away using a crystal radio. No tubes, no transistors, no power. And not just radio, long distance TV reception was vital so they had magnificent tuners back then. I had an old TV not too long ago that still had some tubes. I could get stations 200 miles away on rabbit ears. Can’t do that with a modern TV.
There is no market for excellent reception. People buy crap. So the manufacturers only make crap. Edwin H. Armstrong would be horrified.