From: spam@spam.com   
      
   On Fri, 5 Jul 2013 10:44:26 -0700, dplatt@coop.radagast.org (David   
   Platt) wrote:   
      
   >>>Does anyone see an issue with mounting a pre-amp for a attic mounted   
   antenna in   
   >>attic with the antenna ?   
   >>>   
   >>>Will the attic heat cook the pre-amp ?   
   >>>   
   >>>Thanks   
   >>   
   >>I design such equipment, and we life test it for a month at 85C. It   
   >>has to meet spec all through that - and down to -40C. It'll be ok   
   >   
   >I'd expect that there may be somewhat reduced long-term reliability   
   >due to the heat... continued high operating temperatures are   
   >notoriously bad for electrolytic capacitors.  A preamp designed for   
   >commercial-grade service, and built with high-quality 105C capacitors   
   >would probably be less subject to trouble than designed-to-be-built-   
   >cheaply consumer-grade junk.  You often get what you pay for :-)   
   >   
   >Some of those cheap "mount on the mast" preamps and "active antenna"   
   >systems have caused real problems in the past.  There was an incident   
   >a few years ago in which one or two of these were installed on boats   
   >moored in a harbor here in Northern California.  Under certain   
   >conditions they'd "go unstable" and break into spurious oscillation   
   >(always a risk for any amplifier) and they were squealing enough UHF   
   >noise back out through the antennas to saturate and blank out GPS   
   >receivers located within a mile or so of their location.  This is a   
   >Very Bad Thing for captains who are trying to enter a fog-bound harbor   
   >safely!   
   >   
   >   
   >   
      
   There are equations for calculating electrolytic longevity. They use   
   ripple current, voltage and temperature. 30 years minimum is the spec   
   I work to. In practice, they last a lot longer   
      
   d   
      
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