[TowerTalk] ARR Preamp Failures

[Jim Brown]

On Tue, 05 Oct 2004 09:16:39 -0500, W0UN -- John Brosnahan wrote:

>So I owe K9YC an apology--ASSUMING he is using the 160 watt model.

Apology accepted, although not needed. :) I appreciate the input. 

The failure mechanism was the FET, not the relay.  

I appreciate all of the responses on this, nearly all of which make sense. But if, as you 
say, 

"RF switched preamps are PRONE to this type of problem by their very nature.  The 
sensitive FET gets clobbered with RF for as long as it takes the preamp switch circuitry
to detect the RF and actuate the relay."  

why would ARR sell a mast mounted preamp that relied on that and specified it's 
performance?  ARR's data sheet and instruction sheets say that the unit CAN be hard 
switched IF a suitable pre-keying system is used (virtually all modern transceivers and 
power amps do this, and many transceivers have a pre-delay output). But the ARR 
documentation does not make even the slightest suggestion that this method is 
preferred over auto-detect operation.  

Remember -- when it fails on top of a tower, it can be a very big deal to repair/replace, 
and requires climbing twice -- once to pull it down for repair, once to re-install it. And 
you take your life in your hands climbing a Chicago roof in the winter! 

And how is a ham radio product that is designed to go on a tower not a topic for tower 
talk?  Did I miss something?  

Jim K9YC