Excellent explanation!
There should be better info in the handbook and all companies making these
toys should have properly designed power interfaces.
Thanks
K6EXO
-----Original Message-----
From: Jim Smith <jimsmith@ns.net>
To: amps@contesting.com <amps@contesting.com>
To: <amps@contesting.com>
Date: Friday, December 25, 1998 8:40 PM
Subject: Re: [AMPS] Line input wiring
>
> Hi everyone,
>Sorry to keep going on about this same topic, but I just couldnt let this
>one die while I thought so many people have a misunderstanding on the
>subject. Im relatively new to ham radio, and joined this reflector to
learn
>more about amplifiers, but I do know electrical.
> I think that many people dont know the difference between a chassis
>ground, and an equipment ground. The symbol for a chassis ground looks
>something like this:
>
> _I_
> / / /
>
> The symbol for an equipment ground looks something like this:
>
> _I_
> =
>
> Sorry for the poor representations, its the best I could do with a
>keyboard, but I think you can figure it out.
> A chassis ground is not a ground at all. A chassis ground is a neutral,
>or common conductor. The chassis is used as this common conductor for ease
>of construction. It allows the manufacturer to do a lot less wiring. The AC
>line connection to this chassis ground will carry the imbalance between the
>2 hot conductors back to the panel. This conductor is defined by code as a
>neutral conductor, and is necessary for proper operation of the amplifier.
> An equipment ground is not necessary for the operation of the
amplifier,
>but does make it safer. The NEC forbids using the equipment ground as a
>conductor. The equipment ground should be bonded to the amplifier case,
>which should be isolated from the chassis that the components are mounted
>to.
> A local man knew just enough about electricity to be dangerous. He knew
>that the neutral was tied to ground in the panel, and tied the two together
>elsewhere when he lost continuity on one. He learned just how little he
knew
>when it resulted in his daughters death. Some of my best customers are
>former do-it-yourselfers that learned the hard way to call an expert.
> A few of the reasons a ground should not be used as a conductor are:
> 1. Grounds are often sized smaller than the conductors.
> 2. A ground may be run by itself, and a conductor may never be.
> 3. Grounds may take a path not allowed for conductors.
> 4. Conductors require more protection from physical damage than
>grounds.
> 5. A ground may be something other than wire for part of its
>length.
> I looked in my ARRL Handbook at an amplifier plan. It showed a 4 wire
>plug being used, with the chassis ground attached to the neutral, but did
>not show what to do with the equipment ground wire. I looked at my recently
>acquired Dentron DTR 2000L. It has a 3 wire plug, but no U.L. approval.
> Any amplifier, regardless of brand, or performance is poorly designed
if
>it cannot obtain an U.L. approval due to the fact it forces you to use the
>equipment ground as a conductor.
> So theres my 2 cents.
>Jim Smith, KQ6UV
>
>
>
>--
>FAQ on WWW: http://www.contesting.com/ampfaq.html
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>
>
--
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Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
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