[TowerTalk] Comprehensive Grounding

[Jim Lux]

At 10:19 AM 2/7/2005, kb9cry at comcast.net wrote:
>I'd like to offer a few comments based on my learnings and personal 
>experience.  I am not an expert but do know what I know.
>
>A previous poster made the following comments.
>Those facilities are quite standardized and are often
> > built from scratch. If you want to convince me that a particular 
> lightning protection
> > system - grounds, surge suppressors, etc. - is safe and effective, you
> > have to _test_ it under realistic conditions. We get anecdotes on
> > TowerTalk, but I don't know of any serious testing.
>I'd suggest you talk with the manufacturers of these devices (ICE, 
>Polyphaser, etc.) and find out what type of testing they have done and 
>what are the reports back from their users from the "field".

One might wonder why they don't just publish this data on their website?
(They do publish some results, or at least, advertise compliance with 
specifications that would require testing.  However, there is this little note:
"
Testing can be done on any product. Please indicate the type of testing 
that you need. Testing results to Mil specs such as MIL-STD-462 or equal 
can be obtained in writing only. Some results may be considered proprietary 
and may not be released.
"

Polyphaser does do testing on their components:
"
The let-through energy for PolyPhaser products is determined by testing the 
products with a Haefely PSURG6.1 surge generator equipped with a Hybrid 
Network input module, which will output a surge waveform compatible with 
IEC 1000-4-5 requirements for coaxial products. The surge generator is 
capable of a 6kV by 3kA combined waveform.

Products are connected to the surge generator through antenna or surge side 
connector of the device under test (DUT). The surge let-through energy is 
measured by capturing the voltage waveform on the equipment or protected 
side of the DUT with an H.P. 54522C oscilloscope through a length of line 
which has the specific impedance compatible with the DUT (50 ohm coaxial 
line, twisted pair line, etc.).

The digitized captured waveform is then mathematically processed to 
determine the let-through energy.

Our largest surge generator can produce up to 100kV and 65kA 8/20µs 
waveform IEC 1000-4-5.
"

However, what's really important (at least according to the ap notes) is 
the system, not just the components.  That's where the unbiased advice is 
needed.

And, anecdotal results from the field are useful, but, in many ways are not 
necessarily sufficient.  Field reports are "self selected" (you don't hear 
about the successes as often as the failures).  A manufacturer also has 
very good reasons to not publish all their customer data.




> > > What I want to know is how I can make the best installation in my
> > particular residence with my particular array of trees, utility lines,
> > etc.without spending too much money . It's never going to be easy to
> > use a standard developed for an industrial situation.
> >
>Amateur radio/antenna/tower installations are no different than a 
>commercial installation, the same laws of physics and nature apply.  So 
>don't kid yourself.  Maybe the real question/problem some folks have with 
>the guidelines/standards is summed up in the following phrase, "without 
>spending too much money ".
>Many folks have a problem with doing it the "right way".  Again, 
>physics/nature/lightning don't care if you're a commercial installation or 
>an amateur installation.

The physics may be the same, but the financial (or other) impact of a 
failure is very different between commercial and amateur installations.

A commercial installation is going to be concerned with revenue, and 
"keeping it on the air".  The owners don't like having to write checks for 
new equipment to replace the destroyed stuff.

An amateur installation may be willing to take the outright destruction of 
the equipment in an unlikely event, as long as nobody dies or is injured.

And, that's what's missing from the commercial literature.  The commercial 
literature is (correctly) aimed at keeping the radio on the air.  There's 
not a heck of a lot of guidance for the ham who just wants to make sure the 
house doesn't burn down.  A perfectly viable strategy for a ham may be to 
consider the antenna switch as a "fusible link", something that would be 
unacceptable in a commercial installation.






> > So I end up with an _amateur_ installation, hopefully using enough of
> > standard practices that my station and I will survive the most likely
> > environmental threats. And with some luck, I will even be able to work
> > some DX.
> >
> >
>So to sum it up, life is a series of choices.  You can read the 
>literature, talk to the vendors, solicit suggestions from other and then 
>make a choice.  And then you take your chance.  Gd luck to all, Phil KB9CRY


Jim, W6RMK