[TowerTalk] Ground system design, RF vs AC

[Martin AA6E]

Maybe - If your equipment is grounded via the green AC wire (third pin)
AND to a separate ground, then you have to expect some current will
flow from one "ground" to the other under various fault or surge
scenarios.

A lot of rigs now don't have a 3-wire power connection, but rely on
external 12 volt supplies, whose outputs could be floating with respect
to the AC third wire ground.  Potentially (no pun), that's a good thing
if you want an isolated system.

My old TS-520S has a 2-wire AC cord, which I always thought was the
right way to do it, if you can trust the user to attach his/her own
ground system.

73, Martin

--- Keith Dutson <kjdutson at earthlink.net> wrote:

> >If you cross-connect your ham & AC power grounds, any such fault
> currents
> will flow in your ground system too, for better or worse.
> 
> AFAIK, every piece of ham gear that uses a three prong AC cord has
> the
> safety (green) wire securely attached to the chassis.  If you attach
> a
> ground strip from the chassis to the ham system ground, does this
> meet your
> definition of "cross connect"?
> 
> Keith NM5G
> 
> -----Original Message-----
> From: towertalk-bounces at contesting.com
> [mailto:towertalk-bounces at contesting.com] On Behalf Of Martin AA6E
> Sent: Friday, February 25, 2005 3:11 PM
> To: keith at dutson.net; towertalk at contesting.com
> Subject: Re: [TowerTalk] Ground system design, RF vs AC
> 
> Keith,
> 
> I believe "fault" is the general electrical term for power going
> where it
> shouldn't.  That's why we have protective system grounds in AC
> systems.  If
> there is a short circuit in an appliance connecting the hot side to
> the
> chassis, a fault current flows in the ground lead and the user is
> protected.
> 
> A GFCI detects even tiny fault currents and shuts off the circuit
> asap.
> (It detects a difference between hot & neutral current, as you
> suggest.)  That's a good thing, but old-fashioned fault protection
> involves
> blowing the upstream fuse or breaker with an overload current.
>  That's one reason why your branch circuit wiring has to be matched
> to your
> breaker - to be sure it will trip quickly if there is a short.
> 
> If you cross-connect your ham & AC power grounds, any such fault
> currents
> will flow in your ground system too, for better or worse.
> 
> -Martin (who is not an electrician)
> 
> --- Keith Dutson <kjdutson at earthlink.net> wrote:
> 
> > You wrote:
> > >The problem with connecting the AC green wire to the radio room
> > ground and
> > then connecting my bulkhead "SPG" to a new ground rod or even a 
> > perimeter ground connection is that my radio installation becomes
> part 
> > of the AC protective ground system for the house.  That is, any
> house 
> > fault or other current will partly be routed through my radio
> ground 
> > system. Is that what we want?
> > 
> > When you say "house fault" I assume you are referencing a ground  
> >fault  circuit interrupter (GFCI) system.  Such a system interacts
> with 
> >the  white  neutral ground, not the green safety ground.  So the
> answer 
> >is yes,  we do  want the safety ground connected.
> >...
> _______________________________________________
>