[RFI] DSL surge protection

[Martin AA6E]

Jim,

I agree that losing a DSL modem is not the end of the world.  But
losing my computer is pretty bad.  The rule is that all wires coming
into the shack have to have overvoltage protection referred to the
local SPG.  So, I should do something on the phone lines.  The spark
gap + dsl modem sacrifice might protect the rest of the network.  

That's not completely clear, however, because my modem and Ether/wifi
router have no concept of "ground" -- no place to tie to my SPG. It's a
plastic box and a wall-wart.  Maybe I could go in and find a groundable
point on the PC board, but the boxes weren't designed for that.

A fall-back would be not to worry about the telco line, but to protect
the Ethernet connection from the modem to the rest of the network.

By the way, the 3.3 ohm resistors - I can't easily tell if they're WW
or carbon.  They have a dull coat that might indicate WW.  Of course
the whole unit was sold for DSL use, which you might think would imply
benign frequency response!

73, Martin AA6E


--- Jim Brown <jim at audiosystemsgroup.com> wrote:

> On Thu, 24 Feb 2005 10:59:28 -0800 (PST), Martin AA6E wrote:
> 
> >I am working on a comprehensive surge grounding system for my
> station
> >that will include my computer and DSL gear.  I found the ideal
> >protection device, I thought, but there were surprises.  Namely, my
> DSL
> >modem would refuse to sync on the "protected" signal.
> >
> >See my write-up at http://blog.aa6e.net.  I'd appreciate hearing
> from
> >anyone who has worked in this domain.
> 
> I suggest that you consider the networking hardware as sacrificial
> --it's all 
> cheap gear and from what you say, difficult to protect while still
> working well 
> -- and pay more attention to damage to computers and ham gear that
> can result 
> from pollution of the ground system by MOV-based surge protection
> systems. See 
> the discussion of this issue in the Power/Grounding White Paper on my
> website.  
> 
> Jim Brown  K9YC
> 
> 
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