From: damian@wshb.csms.com (Damian Centgraf - WSHB Engineer)
Subject: transmitter safety / highvoltage shocks (Long) 
Originator: wdp@gagme
Organization: WSHB, Herald Broadcasting Syn., Inc., Cypress Creek, SC, USA 
Date: Thu, 20 Aug 1992 22:07:33 GMT

>From: eds1!compnect!frackit!dave@psuvax1.cs.psu.edu (Dave Ratcliffe)
>Message-ID: <1992Aug13.215240.13502@gagme.chi.il.us>

....[stuff about lightning hit deleted].....

	I've heard of people working on equipment in a lightning storm
	I really can't understand why anyone would take the chance on
	being hit by lightning via hit to the tower... the incoming
	electric service... or even the phone line, though this is rare.
	Even if the station manager is breathing down your neck to get
	you back on it's not worth losing a life over.


>Using the kind of intelligence only a Chief Engineer
>can muster he bypassed the safety interlocks on the back door (see, my
>mama always told me clothspins were good for SOMEthing!) and proceeded
>to start taking voltage readings on the inside of the front panel. To do

	Interlocks are installed for a reason... SAFETY...PERSONAL SAFETY.
	I know there are times when interlocks need to be defeated.
	But a strict safety procedure needs to be implemented and followed.
	NEVER work alone when working around defeated interlocks.  If this
	means getting one of the annoucers or even a friend to stand by
	and know ahead of time where the breakers are to shut off the 
	piece of equipment you are working on.  And if necessary how
	to shut off the incoming service breaker.  Better a dark building
	then a dead individual.
		As for the clothes pins I'm not sure it you meant to use
	them for defeating an interlock? or to hold the probes... I would
	not reccommend either!

>that he had to reach PAST the modulation transformer, only a few inches
>above the spark-gap on the terminals. He was being VERY cautious in most
>respects.... no jewelry, left hand behind his back, rubber soled shoes

		No jewelry...that includes watches, rubber mats, rubber
	soled shoes, and left arm behind the back are all good, however
	the Chief should have NEVER been in that transmitter while it was
	hot....NEVER< I repeat > NEVER been in a hot transmitter.  Inter-
	locks when jumpered around create a HUGE safety hazzard.  
	
		IF it is necessary to take readings while the transmitter
	is on turn the transmitter OFF and hook up you meter.  Set the
	meter on the floor or a cardboard box.  Stand back and turn on
	the transmitter and get your reading.  DON'T TOUCH THE METER 
	while the transmitter is on.  If you need to get other readings
	turn the transmitter off use the GROUNDING STICK!!!! then move
	your meter probe stand clear of the transmitter and again turn
	the transitter on and get your reading without touching the meter
	even if the meter is out of range.  DON'T Touch IT.  Some may
	consider this to be excessive but if it can save your life
	isn't it worth the little extra time that it takes?

>on a rubber mat. I was about 3 feet to his left reading the DVM and
>taking notes while he watched where he was putting his hand. Unfortunately
>he forgot to watch where he was putting his arm and drew a healthy arc
>from the point on the front panel he was testing, THROUGH his arm and
>onto the spark-gap terminals on the modulation transformer. The station
>was running a talk-show at the time so it could have been worse if the
>modulation had been cooking up around the 97.5% we usually hung at with
>music (yeah, compression was AWFUL but that's what the bosses wanted). 
>
>The BANG blew him back from the transmitter (which merrily recycled 3
>times from the surge) and into a cinder block wall 4 or 5 feet back. 
>The remains of the Sencore probe wound up several feet away by the back
>of the 1kw Gates standby transmitter and the DVM itself was sitting on
>the floor with the display flashing something incomprehensible.  Jeff

	.... [stuff about scolding and being incoherant deleted]...

>lucky ones. If he had had his left hand on the cabinet he could have
>been dead. 
>
>				   We buried the melted probe with
>honors under the center tower and christened the gravesite with Iron
>City beer and Kodiak Cream Ale. It was a touching ceremony :)
 ^^^^^^^^^     ^^^^^^^^^^^^^^^^
	It's a good thing the commission didn't show up that day they
	would have added insult to misery and given you a fine.  I can't
	condone the use of alcohol or drugs around something so dangerous
	and WILL NOT WORK WITH SOMEONE UNDER THE INFLUNCE!!!!  They can
	hurt or kill you through their negligence.

>The moral of the story? Those interlocks are there for a REASON! USE
>them!

>From: ampex!newsq@decwrl.dec.com (Stan Busby)
>Message-ID: <1992Aug17.061003.6247@gagme.chi.il.us>
>
>In a recent posting, someone described the result of 
>high-voltage shock.  The results might have been very
>different had the voltage been DC or 60 Hz.  RF tends
>to flow on the surface of a conductor.  The higher the
>frequency, the thinner the surface.  This is why many
>waveguides are silver-plated inside.  Since the current
>doesn't flow so much through your internal guts, especially
>the heart, it is unlikely to kill you.

	Even though there is a "skin effect" with RF it can still kill
	you dead!!!  Don't think that just because it's low power RF
	it won't!  Everyone has a different tolernce to electricity and
	RF, what might kill one won't kill another.  Always treat it
	as it could kill you.

	...[mysteries of RF deleted].....
 
>I have grabbed ahold of 450 volts DC and I can verify that
>DC is harder to let go of than AC.
> 
>While on the subject, a current through the chest of less
>than one milliampere usually does no harm and may not even
>be felt.  Between 10 mils and one amp, electric shock can
>cause fibrillation of the heart, from which you can die
>quickly.  Somewhere between 1 amp and 5 amps, the heart
>freezes up and stops, but generally starts up ok when the
>shock is over.  Emergency rooms have at least one
>"defibrillator".  If you go into fibrillation for natural
>reasons, they put the paddles on your chest and discharge a
>great whacking capacitor through you.  Think of it as
>a kind of one-time sync pulse.
> 
	You just can't make generalization like that.  EVERYONE
	is different.  Always treat equiment as it's hot and 
	you won't need to worry about getting a shock or electricuted!

>Another thing to remember about high-voltage RF.  The thick
>rubber gloves often worn by power company linemen is no
>good at all at 5KV of RF.  After a hurricane, we hired
>a line crew to retighten our transmission lines.  Before
>I had a chance to switch towers, one of the linemen put
>up a ladder and tried to shake the line.  His glove, and
>hand, looked like somebody took a Chinese meat cleaver to it.
> 
	You can't shield yourself from RF by rubber gloves...
	only an adequate amount of space between you and the
	conductor can protect you.  And Yes open feed feedline
	is very dangerous.  Always treat it as hot and always
	ground it before working on it.
	
>The only time I ever shorted out the cabinet interlocks, 
>(This at WTAR-TV), the FCC inspector showed up, caught me
>and wrote me up. 
 

		Safety is such a key item and yet so many people
	take it for granted that the grounding circuit is working
	or that someone else grounded it.  Only you can ultimatily
	be responsible for your own personal safety.  Take the time
	to check that you are safe!  The life you save may be your 
	own!!!!
-- 
       Damian L. Centgraf II        | "Take the key unlock the door" 
      WSHB-Broadcast Engineer       | "See what your fate might have in store" 
 INTERNET ...damian@wshb.csms.com   | "Come explore your dreams creation"
      COMPUSERVE ...70571,313       | "Enter this world of imagination" -Rush


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