[AMRadio] Amazed any young ham made it to adulthood


sbjohnston at aol.com sbjohnston at aol.com
Mon Jan 19 23:27:52 EST 2009


Hey, *I* was there...  It was at my "Boat Harbor" transmitter site at 
WGH in Virginia.

What a hoot - the #2 of a combined FM transmitter was on fire and Fred 
opened the cavity door and bent over to try to blow out the fire.  But 
the blower was blowing a huge amount of air on it already - how else 
can you get teflon to burn?!  I just turned off the other transmitter 
and killed the blower breaker and the fire stopped immediately.

The trouble was that we didn't know that the reject load was no longer 
50 ohms, and when we shut down the #2 transmitter, RF from #1 got back 
into #2 via the now-unbalanced combiner, arc'ed over the plate blocker 
and set the insulating shelf on fire.

It had happened before at that site (before Susquehanna owned it) when 
no one was around and burned up the entire transmitter.  The Chief 
Engineer lost his job over it - but it wasn't his fault, it was those 
terrible oil cooled Bird loads.  I switched to an Electro-Impulse air 
load for the reject and the trouble never happened again.

I wrote an article about it for Radio Guide - see

http://www.wd8das.net/RCAfire.JPG


Steve WD8DAS

sbjohnston at aol.com
http://www.wd8das.net/
-----------------------------------------------------
Radio is your best entertainment value.
-----------------------------------------------------


-----Original Message-----
From: BILL GUYGER <bguyger at sbcglobal.net>
To: Discussion of AM Radio20in the Amateur Service 
<amradio at mailman.qth.net>
Sent: Mon, 19 Jan 2009 10:10 pm
Subject: Re: [AMRadio] Amazed any young ham made it to adulthood










Steve

This isn't going to mean a thing to the rest of the list, but your 
story
reminded me of the tim Fred Greaves got his picture taken when he 
opened the PA
cavity door of a FM transmitter that was off, but the cavity was still 
hot with
RF from another transmitter getting back through the combiner. At least 
I think
those are the facts, I've slept since Norm Philips told me about it.

Bill AD5OL



----- Original Message ----
From: "sbjohnston at aol.com" <sbjohnston at aol.com>
To: amradio at mailman.qth.net
Sent: Monday, January 19, 2009 8:20:33 PM
Subject: Re: [AMRadio] Amazed any young ham made it to adulthood


The shock I experienced did not deter me - it just made me more
careful.  And now I have over 25 years as a broadcast engineer working
with plenty of high, low and indifferent voltages.  I've been shocked
a few more times, too.  But I still have the good habit of only using
one hand on live gear.  The other hand is down my pants, er, I mean,
hooked in my belt around the back.

Steve WD8DAS

sbjohnston at aol.com
http://www.wd8das.net/
-----------------------------------------------------
Radio is your best entertainment value.
-----------------------------------------------------


-----Original Mes
sage-----
From: CL in NC <mjcal77 at yahoo.com>
To: amradio at mailman.qth.net
Sent: Mon, 19 Jan 2009 8:00 pm
Subject: [AMRadio] Amazed any young ham made it to adulthood










I thought electric shock was a right a passage.  I tried to build a
Jacobs
ladder as a kid of about 10, using brazing rods, a Ford ignition coil,
and a
Lionel train transformer.  Yes, I knocked the stuffing out of myself,
but I
learned something in the process.  I had a real Gilbert Erector set
too, with
all kinds of sharp metal items, a real 110VAC electric motor, and an
imagination
to build twirling things of great danger.  My first electronic project
was right
out of Boys Life Magazine as a Cub Scout, a 2 tube audio amp,
transformerless I
might add.  Worked like a champ, and not a word of warning in the
directions
about how this could be dangerous, just if it hummed  turn the AC plug
around.
The only 'real' shock I have endured was from my GE Prog Line, I had
mounted to
a 19 inch rack panel with speaker, discriminator meter, volume,
squelch, and a
pot to adjust the screen voltage of the final to change power out.  It
was on,
and I needed to turn it
  over, and when I reached around both sides of the radio chassis, I
grabbed hold
of the 110 in.  The weight of the radio is what broke the connection
when it
shook loose from my hands.

Everything in this=2
0hobby can be dangerous, just like everything in life
is
dangerous.  If you take care in what your doing, you can avoid the
stupid
mistakes, but failures of interlocks, insulation, or tower sections
will claim
even the most careful.  To leave the 'dangerous stuff' to a real
technician is
fine if you bought a Volvo just because it's a safe car.  But, to be
afraid to
open up a piece of equipment after following the safety rules because
it says
'Danger HV', makes as much sense as buying a rifle and never firing it
because
it has the words, "may cause injury or death" engraved on top of the
barrel.

Charlie W4MEC in NC



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