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Re: [TowerTalk] Shack wiring

To: "" <>
Subject: Re: [TowerTalk] Shack wiring
From: "Jim Brown" <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Mon, 15 Mar 2010 10:33:37 -0700
List-post: <">>
On Mon, 15 Mar 2010 08:55:50 -0400, Pete Smith wrote:

>I have my shack wired through a series of plug strips, 


What you're describing is quite common, and at one point I thought it was a 
good idea. It is NOT. There are two problems, both important. First, the 
use of MOV devices on branch circuits is a recipe for lightning DAMAGE, not 
protection. That's because in the event of a strike, they are shorting the 
pulse to equipment ground at the point of every MOV, but thanks to the 
resistance of the green wire, every outlet is at a different (and very 
high) potential. Any equipment connected into outlets at different 
locations with signal wiring between them is likely to be damaged by the 
strike. The more inductance in the green wire, the more likely and the more 
severe the damage. I have heard MANY anecdotal reports of computer and home 
entertainment equipment destroyed by lightning damage. Plugged into MOV 
outlet strips, no antennas at all, only Ethernet connections or audio 
cables connecting them together. 

As to the second problem -- Several years ago, I was asked to fix severe 
hum and buzz at N6RO's 6-transmitter super station just east of San 
Francisco. It had been wired years ago by person(s) unknown, and that 
wiring job was excellent, with steel conduit from a local breaker panel in 
the shack to quad boxes and 240V outlets for each station. Over the years, 
a half dozen multi-outlet strips had been added, rather than use outlets at 
the quad boxes. I measured something on the order of 30mV between each 
computer chassis and the associated radio chassis. That's what was causing 
the buzz. The very simple power wiring and chassis bonding detailed in is the result of that work. 

In about two hours, that station was buzz free. The executive summary is 
that I got rid of all of the strips, plugged everything directly into the 
original good outlets, bonded the outlet boxes together with copper braid, 
and bonded the gear in each station together with copper braid. The only 
material used was about 20 feet of copper braid stripped from some old RG8.

The whole house shunt protector IS a good idea -- if the house wiring is 
proper (that is, all the equipment and grounds bonded together), a strike 
coming in on the power line raises the ground voltage for the entire house 
by the same amount when it shunts it to ground. With that in place, the 
differential voltage due to a strike is limited to what's on branch circuit 
wiring between the panel and your equipment. The only safe way to protect 
those branch circuits is with a SERIES MODE suppressor, such as those made 
by SurgeX or Brick Wall. In essence, they store the strike energy in a very 
robust inductor, then discharge it slowly as a DC current after the event. 
They are not cheap, but neither is our ham gear. :)  

Disclosure -- SurgeX is well respected in the pro audio world, and most 
good consultants have been specifying their gear for 10-15 years. About 
five years ago, they hired me to write a tutorial for them on power and 
grounding, and to teach classes on that topic at trade shows, and I still 
do that. I was specifying their products for nearly ten years before taking 
that commission, and I have a half dozen of their protectors in my 
home/office, all of which I paid for. 


Jim Brown K9YC 


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