I guess I consider myself lucky. In all the years that I've used 12 VDC fans on various configurations of repeaters, I've never had one that created whine. And I've used mostly cheap or surplus fans. The only time I had a problem with fan whine it actually turned out to be an issue with the ground on a third-party controller.
Now that I've said this, I expect Murphy to strike the next project involving a fan ;-) Chuck WB2EDV ----- Original Message ----- From: "Eric Lemmon" <[email protected]> To: <[email protected]> Sent: Tuesday, April 14, 2009 9:11 PM Subject: RE: [Repeater-Builder] Funny noise on repeat audio > John, > > Perhaps you should use DC fans that are designed to be low-EMI. Panasonic > (among several other makers) offers a line of "low-EMI" DC fans that are > specifically designed to minimize or eliminate any conducted or radiated > EMI > during operation. I have used such a fan on a solar-powered repeater, and > have zero interference from it. Some cheap DC brushless fans are made to > a > low price target, and are prolific generators of hum and hash. I have > found > through several years of experience that a high-speed fan- which can > generate acoustic noise- is often not needed. A small, 3-inch low-EMI fan > that runs at a very slow speed is adequate for most applications. A fan > that runs at less than 1000 rpm is usually adequate, and is almost > noiseless > to boot. Nobody likes a whiney fan! > > 73, Eric Lemmon WB6FLY
