[C38] SSB Radio Grounding

[Les]

The counterpoise also carries RF, until it reaches the ocean.  The
wavefront builds according to the physical configuration of the mass
tied to the element (in this case the coaxial sheild), if this is the
only path to ground.  In the case of an engine block and associated
wiring, the RF will or at least can setup a field that puts a voltage
node at the alternator.  This voltage is in essence unconstrained,
consisting of the voltage loops of SWR.  The diodes of an alternator can
handle a lot of current, but their voltage limitatioin is typically 35
or so volts.  The RF loops on 50 ohm conductor are up to 70v at 100w
(the typical power out of a marine HF transmitter).  The possibility
exists that on some frequency the voltage peak could manifest at the
alternator and poof, there go the diodes.  ANd being a boat, Murphy
applies, only in a storm, with other problems as well, then you can kiss
your anode good-bye ;-)

Regards,
Les H

Regards,
Les H
On Tue, 2008-03-11 at 22:07 -0400, Tom T. wrote:
> Les,
> 
> How will "stray" RF burn out the diodes if the RF counterpoise is grounded
> to the block and not to the DC positive side of the alternator?
> 
> Tom Troncalli
> 
> 
> 
> 
> > [Original Message]
> > From: Les <hlhowell at pacbell.net>
> > To: <larrypi at linkline.com>; Catalina 38 Listserve
> <listserve at catalina38.org>
> > Date: 3/11/2008 6:20:31 PM
> > Subject: Re: [C38] SSB Radio Grounding
> >
> > HI, everyone,
> > 	Do NOT do this.  You run the risk of blowind your alternator diodes
> > with stray RF.  The specs call for a separate RF ground for good reason.
> > The engine to ocean ground is via the propshaft, and that doesn't have
> > sufficient planar area either.  Get the 
> >
> > Boatowner's Guide to Marine Electronics  by Gordon West.  You can get a
> > used copy for 6.99 from Amazon.  Read it.  Follow its instructions.
> >
> > 	If you are not a radio amatuer, get the radio professionally installed.
> > It will save you lots of headaches and be more reliable.  If you are a
> > radio amatuer moving to marine means just learning what does and doesn't
> > work.  One thing for sure, get the self sealing tape for connectors
> > (similar to rigging tape).  Use it on all connectors.  The best process
> > is to properly assemble the connector, apply some marine silicon sealant
> > to the fixed part of the shell, then cover that with the self sealing
> > tape.  After the connectors are joined outside, cover the whole
> > connection, starting about 1" back on the cable to as good as you can
> > get beyond the other connector.  This keeps out salt, water, corrosion
> > and curious birds, all of which can defeat your radio's connections.
> > (Old ETC talking here with 20 Navy years behind him.)
> >
> > Regards,
> > Les H
> > On Tue, 2008-03-11 at 10:54 -0700, Larry Malmberg wrote:
> > > Has anyone grounded their SSB to the engine?  If so, how has it worked
> out?
> > > 
> > > 
> > > 
> > > 
> > > 
> > > Larry Malmberg
> > > Hassle Hull 149
> > > 
> > > 
> > > 
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