The first bugs in the old large 1st generation computers were actually insects 
(bugs) that were raising havoc with the insulation.  Hence, "bugs" has become 
our favorite term!

73,

Jim, W7OWI

________________________________
From: elecraft-boun...@mailman.qth.net <elecraft-boun...@mailman.qth.net> on 
behalf of Andy Durbin <a.dur...@msn.com>
Sent: Saturday, November 7, 2020 07:50
To: elecraft@mailman.qth.net <elecraft@mailman.qth.net>
Subject: [Elecraft] Tuner bug

My top band antenna is an OCF wire running round my back yard wall at about 5 
ft above ground.  It has been through a number of iterations to make it tunable 
on 160 and to handle 500 W.

500 W capability was achieved with a home brew feed point L match consisting of 
a large air-spaced variable capacitor and an inductor wound on PVC pipe.  It 
worked fine until the small hours of Saturday morning when the SWR jumped to a 
really high value and tripped my KPA500 reflected power monitor.   Some quick 
tests showed it worked fine up to about 200 W but anything over that gave an 
instant transition from low SWR to very high SWR.  All easily seen in my 
station controller's data log.   It seemed likely there was an insulation 
breakdown somewhere, but where?

Careful inspection of the air-spaced variable revealed a small bug between the 
plates.  It was carefully extracted and viewed under the microscope.  It was 
well charred!

Quick check on 160 m and the antenna will handle 500 W again.  Now ready to try 
for a few missing states in ARRL Sweep Stakes.

Not all bugs are neatly categorized as either hardware or software.

73,
Andy, k3wyc


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