[Hallicrafters]V16#26 - Line Cord/Safety/Capacitors

[Phil Barnes-Roberts]

At 04:00 AM 5/16/05 -0400, hallicrafters-request at mailman.qth.net juggled 
the keys to produce...

>From: Mike Everette <radiocompass at yahoo.com>
>Precedence: list
>Subject: Re: [Hallicrafters] antenna
>Cc:
>Date: Sun, 15 May 2005 10:08:23 -0700 (PDT)
>To: chandlerh2 at aol.com, hallicrafters at mailman.qth.net
>In-Reply-To: 6667
>Message-ID: <20050515170823.62349.qmail at web52106.mail.yahoo.com>
>Content-Type: text/plain; charset=us-ascii
>MIME-Version: 1.0
>Message: 2
>
>For general receiving I'd just put up a long wire, say
>from the eave of the house to a convenient tree.  You
>could put a rotary switch in the line to select which
>radio you wish to use, and just feed each of them with
>a single piece of wire.
>
>Don't forget lightning protection.  The simplest is to
>put a knife switch in the line -- OUTSIDE the house --
>to disconnect the antenna from the radios and run it
>straight to ground.  Always leave the antenna grounded
>except when you are using the radios.

Emphasize that STRAIGHT to ground.  Lightning behaves something like RF (a 
LOT of it!) in that a multi-microsecond (Megavolts at Kiloamps) pulse 
doesn't really want to bend around a corner if it can help it - and it 
can.  If it comes to a sharp corner, the voltage it takes is inversely 
related to the corner radius, to hop off to somewhere else, so make your 
lightning grounds runs straight (slight curve is OK), with as wide a 
connecting strap (wish there was still affordable copper roof flashing!) as 
possible.  If not strap, multiple #4-to-8 wires to multiple ground rods, 
wired together a few feet apart, but all this is yet another discussion; 
good scoop at PolyPhaser, and at < http://www.arrl.org >


>If you leave the antenna connected during a storm,
>current can be induced into the wire from nearby
>lightning -- enough to burn out an antenna coil.  It
>does not need to be a direct strike.
>
>BE CAREFUL with that S-22R (or any other radio with an
>acey-deucey power supply)!!!

This subject of line cords, fuses, and power-line entrance capacitors has 
been covered in some depth on 04/06/05 in this reflector, by K1LKY and 
several others; see < http://www.justradios.com/safetytips.html > for more 
discussion of line cords/safety/the new safety X and Y capacitors.  Mouser 
carries them.

>There are 3 capacitors in the S-22R, all 0.25uf,
>between the chassis itself and the "electrical"
>ground.  There is another, a 0.002 or 0.005 uf, from
>the hot side of the line to the chassis.  BE SURE you
>have changed all these and replaced all of them with
>something rated for AC.  If you don't you are
>GA-RON-TEED to get lit up (been there, done that, not
>fun -- happened before I recapped the radio), and you
>may not need a radio to listen to the celestial
>voices.
>
>Also be sure you either replace or remove altogether,
>all the power line bypass caps in the
>transformer-operated radios, or you may get lit up (or
>at least tingle-ated) if you touch two of them at the
>same time.  These old caps LEAK!  And in the SX-110,
>get rid of that 470K resistor from one side of the
>power line to ground (who knows what the designer was
>thinking when that was specified!! Duh!).  If you
>replace the caps, use parts rated for at least 1000
>volts AC so they will withstand surges.  (In the
>S-22R, the aforementioned capacitors must be in the
>circuit).
>
>Bond all the radios together for common ground -- but
>BE SURE, before you connect the S-22R to the ground
>system, that the radio is plugged in such that the
>chassis is not hot!  Best way to avoid this is to use
>a 3 wire cord.  Connect the black lead to the supply
>side of the circuit (so it goes to the rectifier), the
>white lead to the chassis, and the green lead to the
>ground terminal on the antenna strip.
>
>73
>
>Mike
>WA4DLF

--
73, Phil Barnes-Roberts WA6DZS < Mailto:pbarnrob at acm dot org >
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