Thou shalt have no other gods before the ANSI C standard 1499

In my case, the **** (pronounced the same as the stuff that was clogging your commode in an earlier thread) was radio frequency interference produced by the oscillator in the switching power supply. I had a 555 timer running at appx. 400 Hz that produced harmonics at 800, 1600, 3200, 6400, 12800, and so forth up the scale. One of those harmonics was locking up the receiver.

AM radios are a little different. They pick up more noise, but aren't subject to the "capture effect" found in an FM receiver.

A list of items known to cause RFI would be way too long to list here. Computers are probably the biggest offenders... Strangely, my PDP-11-23 plus is the worst one I have. Kinda ironic that I'm saying that to the Den Mother of DEC. :-)

Some suggestions to resolve your AM reception problem are:

* Make sure that all the computer and radio equipment you own is connected to a nice, solid, earth ground. In the case of a table-top radio, if it doesn't ground the chbuttis via a third prong on the power cord, you can ground the chbuttis yourself to a water pipe or grounding stake.

* Many AM radios use a ferrite core antenna built into the chbuttis of the radio. These are fairly directional and polarized in the horizontal plane. I put my AM radio on a lazy susan and rotate the entire radio to minimize RFI and maximize the desired signal. Kinda hokey but it works.

* If your radio uses an external antenna, you can buy filters (for AM, get a LOW Pbutt filter with a cutout just above the AM broadcast band.)

* Some RFI sneaks in via the power supply. Most times, this is stuff that comes from other devices in the home or connected to the transformer that serves your home. In this case, an isolation transformer and filter on the power supply can limit the RFI that gets in that way. Use caution when putting your radio on a cheap UPS -- the UPS uses a switching power supply to generate the AC -- these often produce more RFI than they eliminate.

* Finally, make sure that your own computer gear keeps its RF to itself. Don't run PC's with the covers off. Keep the system well grounded. Use shielded cables (particularly VGA and thinwire Ethernet.) Make sure that the shields on the cables are connected to ground. Don't forget the other potential radio transmitters in the home: microwave ovens, television sets, VCR's, DVD's, satellite receivers, camcorders, baby monitors, cordless phones, blenders, vacuum cleaners, and just about everything else that uses stuff developed by Tesla, Edison, or Maxwell.