>From a good friend of mine who is a ham: -- Start Email --
You could try to find some sort of industrial low-noise rated PSU, but it's probably not necessary. Switching supplies generate a lot of noise. There's not really any getting around it. But you can do a lot to keep the noise inside the PSU and out of your radio. First of all, verify that the noise is even coming from the PSU. Monitors, both LCD and CRT, are often major noise culprets. Any digital periipheral, mice, keyboards, scanners, whatever, they are all suspect. Use the process of elimination to determine what is really causing the noise. There are two basic approaches to dealing with noise generators: Choke the noise using inductors, or shunt the noise to ground. Shunting relys on shielding, bypass capacitors, and most importantly a good ground system. You know that lump on your monitor cable? What you might not know is that it's an inductor. It's just a tube of powdered ferrite, and it doesn't have very much inductance, but it doesn't take much inductance to choke off RF. Buy a supply of RF noise suppression ferrites, either the toroid type or the snap on type or both, and fit them to all of your cables at both ends. Power cables, USB cables, everything. This is quick and easy and often resolves the issue. You might find some at radio shack or you can order them from teh internets. Your PC is probably already pretty well shielded, but it doesn't hurt to evaluate it. Do you have a big dumb plexiglass window in the side of your chassis? It's leaking craploads of RF energy. Look for any big gaps in the shielding. You can use metal window screen to cover them up. I can't say enough about grounding. All your equipment should be grounded to a single common point which should then be connected to the ground plug on your AC outlet, or even better to an 8 foot ground rod located no more than a few feet from the radio. Don't daisy chain stuff. But wait, some devices actually must not be grounded because their grounds are "floating" and there is actually a voltage potential between their chassis and earth ground. PC chassis are never floating AFAIK. I've never actually blown something up except once when I grounded a radio to a laptop when both were running from a 12v battery but the laptop was using a 12v to 18v DC-DC converter. It burned the ground traces right off the radio's PCB. It's funny because when the laptop was plugged into a real AC outlet I grounded it to the radio with no problems. I had a laptop power supply that was very noisy, I wrapped it in aluminum foil, connected the foil to ground, and put ferrites on both ends of both the DC and AC wires. It helped a lot. Shortening unnecessarily long wires can help too. Coil them up to make them act like an inductor. 73 de n1ywb -- end email -- Stan On Sun, Aug 10, 2008 at 8:30 PM, Anthony Carrico <[EMAIL PROTECTED]>wrote: > Anthony Carrico wrote: > > Mike Raley wrote: > >> Greetings Vaguerites! > >> > >> Does anyone out there have any knowledge of/experience with PC power > supplies that are rated low RF noise? A good friend of mine is into Ham > Radios and is looking for a PC power supply that is either well shielded or > has a very low RF noise component. At this point he has to turn his PC off > to do just about anything. > > It might also be worth checking out any model that is sold in Europe. > They have "power factor" standards, some of the US models follow those > standards too. I think maybe my seasonic supply does. > > The idea is to reduce the amount of reactive power that is reflected off > the load back into the line (which is bad for the grid). I don't know if > that circuitry does much to contain the switching frequencies though, > just an idea. I think there are active and passive versions of these, > which may behave differently. > > -- > Anthony Carrico > > >
