Agreed. Plus, a constantly-operating fan pulls a lot of dust and dirt into the equipment. Besides, the fan is ineffective until the heat sink gets warm, so starting it immediately upon key-up is a waste of energy. In my opinion, a snap-action thermal switch mounted on a heat-sink fin is the simplest and most practical means of controlling a fan. I use a switch that turns on the fan when the heat-sink reaches 120 degrees F and stays on until the temperature drops to about 90 degrees. My preference is a switch sold by Digi-Key as Catalog Number 317-1094-ND.
73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of skipp025 Sent: Wednesday, December 23, 2009 8:24 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Henry Amps > >The question is... do the fans run all the time or do they > >turn on with temperature or keyed with RF or an external > >logic (PTT) line? > > > >It's pretty bad listening to fans whining at a radio site > > A spinning fan is a working fan. Also kind of hard for a > mouse to build its nest in a spinning fan. A constant spinning fan makes unnecessary noise, consumes energy and wears out much faster. If there's a mouse in the works, chances are they most often migrate toward warm parts in the power supply section and you'll have a much bigger program down the line. "Bite Blocks" for the Mouse and all will be quiet... s.
