Radios & Interference TOC RADIOS SOME GOOD RADIOS CRITERIA INTERFERENCE RADIOS Most modern radios do not receive AM very well, since it is considered less important than FM. SOME GOOD RADIOS Three that are designed to receive AM well are: GE Super Radio The current is model III, often available at large drug stores). (The original model is reputed to have even better performance. Model II is OK though some early ones had sensitivity problems due to a bad FET in the front end. One report indicates it should work down to about 30. microvolts, comparable to a good Delco automobile radio. Model III has varactor tuning to 1700 KHz.) I believe it has its own extendible rod antenna, and terminal pairs for external antenna for both AM and FM. Under $100 if I recall correctly. Two friends have had success with that radio. Radio Shack "Extended AM Range" radio. (Part of their Optimus line of equipment.) Has single terminal for external AM antenna (as well as three different connections for different types of external FM antenna), as well as its own extendible rod antenna. About $60. One friend had success with that radio. (The foregoing portable AM radios may be made in Communist China.) A new design available from the C. Crane Co. 1-800-522-8863 has some neat auxiliary features and claims to be an excellent AM radio. Their price was $150. when I last checked. (The radio also receives FM, and may receive weather broadcasts.) Two similar radios made for good tuning and reception have been recommended to me: - the Uno, from Tangent-Audio.com, has an analogue tuning dial, connection for external FM antenna, and various auxiliary inputs and outputs so you can get music from a portable CD player or tape player and use amplified external speakers. c Crane sell it. Tangent also sell a clock radio version named the Duo. Clean Euro-look styling. - the Tivoli Audio radio is similar to the Uno and also comes in a clock radio model, plus has a companion external CD player. Styling is more North American than the Tangent products. Typically these radios have only one speaker but an output for a second speaker to get stereo and some auxiliary stereo input and output jacks. Priced around $120 to 160. More expensive multi-band radios are available but I do not know how good they are on AM - often they are sold for receiving distant stations but their emphasis may be on "shortwave" frequencies. Some people get good results with old "console" radios that were built into cabinets with record players during the 50s and 60s when AM radio was more important. I expect you can buy those for a low price. If you try to take the radio out, look for hidden antennas. I am advised by people DXing for oldies music that the following radios are very good. (So ask a collector (ham radio enthusiasts are suspects) or someone who frequents antigue shops or swap meets to look for them?) McKay-Dymek AM3 or AM5 tuners (wide band, AM-only, made in Australia, probably old component stereo type packaging from the days of separate tuner and amplifier units) Radio Shack model TRF, sold in mid-70s. As well, if you have a GM or Chrysler factory car radio from the 60s or 70s, they usually are strong (built for the wide open spaces of America with long distances between stations). Even such radios from the 90s can be better than household and portable radios. In contrast, Japanese car radios from the 60s and 70s did not have such performance. If you are chasing music, keep in mind that AM stations do not reproduce the lowest and highest frequencies, and that many "oldies" recordings were low budget efforts - some of the most popular were recorded in a garage. CRITERIA In any case or location, you will need a radio with good selectivity, since some of the stations you want are low-powered and bracketed by strong stations which can spill over. (I've even had sidelobes of a strong FM station interfere.) Digitally tuned car radios should have good selectivity, as does the GE SuperRadio (I have not tried the Radio Shack one nor the Crane one which is digitally tuned nor the Tangent and Tivoli analog tuning ones). INTERFERENCE AM signals are much more sensitive to interference than FM, and here we are trying to get weak signals. Interference may be quite local - often due to power lines and things in your building. If you have interference, try moving your radio around your building, as your own appliances could be the source (light dimmers, low voltage lights, and halogen lights are common offenders - turn appliances off one at a time and note any difference). (It is possible to filter lights etc., but takes good expertise to be effective and safe.) Also try orienting the antenna in different directions, which may reduce noise pickup and enhance pickup of wanted signal. And change the direction of power and headphone wires - I've had success with that. (And with the ultimate - sit with the radio in your hands, as your body may intensify the signal.) If the interference is across a broad range of frequencies, a better radio or external antenna may help as I'd suspect the coupling path could be through the power wire (try running on batteries to see if it makes any difference). There are filters that could be used, but that's getting into technical work. If you have a good computer surge protector try it with your radio, without the computer - the good ones have a noise filter. For power wire interference try a toroidal core as used on computer cables. Some simply clamp on the wire - first wrap as many turns of the wire as you can around half the toroid, then close it. If you can't find suitable toroids locally, try the T130-26 from Amidon Inc of Santa Anna CA, 714-850-4660. Loop antennas are usually more noise-resistant than long-wire antennas as they are less sensitive to lightning and electrical arching. They are directional so will not pick up noise and other stations from the sides. Also, consider borrowing someone's known good radio to see if it is better at rejecting your local interference, thus worth purchasing. You might try your car radio, as it is not connected to the electric power wires (and it may be a better radio than you have in the house). Some people have reported problems when a power wire on the street had a corroded connection. They localized the problem by walking down the street with an AM radio tuned to a blank frequency, listening for maximum static. As well, it may help to know the frequencies of strong stations in your area, with frequencies near the station you want, and their type of programming, to help identify the signal you want. Tuning dials are coarsely marked and may not be not accurate - recognizing a nearby strong station helps zero in on the signal you want by starting tuning at the strong station. If anyone gains experience that would add to this, please let me know. ------------------------------------------------------------------------- Copyright Keith Sketchley 2008.09.2024 (1009PDT) Legalities detailed on http://www.keithsketchley.com/ apply. Use of advice and information contained in this file is at your risk. ------------------------------------------------------------------------- BACK in your browser should return you to the page you came here from. See http://www.keithsketchley.com/antennas.txt for related information.