[aprssig] Wholehouse Surge protection?

[Al Wolfe]

    First off, I have been a broadcast engineer and consultant for about 
forty years and a licensed commercial electrician for thirty years. I have 
hardened many sites for lightning protection as part of the job. 
Broadcasting facilities don't have the luxury of shutting down every time a 
thunderstorm is forecast. We have to carry on.

    A whole house surge protection will provide a degree of protection from 
surges on the power lines, provided that it is installed properly according 
to the instructions, normally attached directly to the entrance panel.

    But it is only part of the protection plan. Don't bet the rent on it. 
Protection at the equipment end is just as important. As hams we are 
probably more exposed to damage from currents and voltages induced onto our 
antenna structures by lightning than from those on the power lines. It's 
along way from the back of the rig to the suppressor on the entrance panel 
for a lightning induced current. The whole house surge suppressor will 
probably do nothing for antenna system lightning charges.

    (So, how do you know your protector is working if it fails open? If the 
breaker tripped what does it mean? How do you test it? How many folks happen 
to have a hi-pot tester laying around?)

    As someone mentioned, lightning behaves much like RF. It has an RF 
component broadly peaking from 100 KHz. to 500 KHz, but contains energy 
literally from DC to light. RF hates ferrous materials and will usually take 
a copper path if given a choice. I have solved several stations' lightning 
problems simply by running all the feedlines and other cables to the tower 
through four inch or so, EMT (electrical metallic tubing (steel)) used as a 
choke. Of course these line are  grounded at each end of the EMT. A little 
series L, the conduit, makes the lightning seek an alternative path, the 
ground rods at the base of the tower.

    Probably as important as grounding is the concept of bonding everything 
together so when one does get hit (not if) all the equipment rises and falls 
at the same potential. I use copper straps from two to four inches wide for 
my professional work. Then these straps all run to a common point ground. 
Alternatively, one can use copper tubing if it is flattened at the end for 
attachment purposes.

    For a home station ideally all feedlines, including those for APRS, need 
to come through a copper bulkhead that is properly bonded to the common 
ground.

    I do not normally use braided bonding cables, especially outside. 
Exposed to the elements they oxidize in a few weeks or months and becomes 
worthless for anything but DC current. (Well, the shields from real RG214 
are probably OK for rig bonding as they're silver plated and used indoors.)

    FWIW, the Polyphaser website has some very useful info about the 
grounding picture and concepts.

73,
Al, K9SI, retired, mostly