[TowerTalk] A different question (I think) on SPG

[Jim Brown]

On Wed, 4 Aug 2010 15:31:22 -0500, Bill Aycock wrote:

>Jim--
>In the answer you posted Z(below) you said:
>>
>> All equipment in the shack should be bonded together by very short, beefy
>> copper. This combination of bonds is what goes to the earth electrode.
>>
>This is NOT what the grounding instructions say in my Yaesu FT-950 manual.
>Traditionally, this list adheres to :  "Do what the manufacturer says". 

Hi Bill,

I have NEVER said that as a blanket statement, and I probably never will (except 
on the rare occasions when they happen to be right). Yaesu is not going to 
replace your radio or your house if they are damaged by lightning. Further, it 
is VERY common to see outright errors in manufacturer manuals. They are 
repeating past folklore. Hell, they can't even build radios without pin 1 
problems -- you expect them to get anything else right? :) 

>I am 
>getting several interpretation of "SPG" here, and am confused. In the past, 
>I have read your posts with close attention and admiration; I need a 
>clarification.

Then re-read them. :)  I've tried to not contradict myself and to write clearly. 

>Another question: You mention "Short, Fat" as desired form for connections 
>here, but in many other places, "Short, Flat" (as: Copper strap) seems to be 
>preferred, as having low inductance and lots of area for "skin" effect.

There are two considerations. Low resistance for minimum audio frequency noise, 
which translates to short and beefy. Low inductance for minimum impedance to RF 
(lightning), which translates to short and wide. Skin effect causes RF current 
to spread to the outside of conductors, so a FLAT conductor will see most of the 
current at the edges. It thus becomes two conductors in parallel. Most experts 
agree that MULTIPLE parallel paths between the the equipment and the ground 
offer the lowest impedance, and for that reason, most building codes tell you to 
bond neutral to BUILDING STEEL, which offers multiple paths to the earth. 

73, Jim Brown K9YC