At 12/21/2008 09:24, you wrote: >Some of our local "start-up" radio clubs throwing repeater >packages in place often start out using and stay with an >external RF amplifier designed for mobile operation. Sometimes >the amp runs so hot you can't keep your hand on the heat sink >but I've yet to see one fail. > > >cheers, >skipp
70 °C, the upper operating temperature limit of many RF devices, is too hot to touch. However, MTBF will definitely be reduced. In addition, without better cooling the devices & board will experience greater temperature extremes, which would result in more failures caused by thermal cycling. Mobile amps often lack adequate power supply bypassing, resulting in a lot of in-cabinet RF coming off the amp's power leads. This can be avoided by feeding the +12V through bypass capacitors or high current EMI feedthroughs, & rerouting the - power connection directly to the case instead of through an unbypassed terminal strip. Bob NO6B
