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Grounding/Bonding: Was Re: [Elecraft-K3] Factory service still available?

Clay Autery
 

I did not answer the original questions:

How would you measure that impedance? Between which two points?
Lou KE1F

2nd question first....  between ALL of them, from end to end...  Wherever the lightning event may travel....
How?  "It is commonly measured by using a frequency generator and an oscilloscope or an LCM multimeter."

You COULD do it with a combination of mathematics and instrumentation....  In those parts of the SYSTEM where you can calculate the resistance and inductance mathematically, you could do so.
In the "choke points" and/or places that don't lend themselves to mathematical computation, use the instrumentation....  EVEN THEN, you will have to make measurements on time scales and frequencies attainable, and then use math to get "true"er readings for the time frame, frequency, et al. of the lightning event level at which you are engineering protection.

Not all lightning events are the same, local, direct, indirect, same energy level, etc, etc....  You have to PICK an engineering standard and design toward it.

73,

______________________
Clay Autery, KY5G
(318) 518-1389
On 05/10/20 11:30, Clay Autery wrote:

Lightning events happen in a VERY short time period... 

As I understand it, the conductors that you are using in your lightning protection system to BOND all the chassis together and thence to your entrance panel, and thence to your grounding system (rods, horizontal connectors, et al) need to be LOW INDUCTANCE.

IF I still grasp what Jim, et al. have been trying to teach us about lightning protection vs. RFI prevention....

The GOAL is to keep our stations at the same ground potential as where we want the lightning energy to GO....  Because the lightning event IS going to enter your shack if the event occurs close enough to ANYTHING connected to it.
Thus, the GOAL is to keep the energy from the lightning event on the grounding conductors and on the outside of the devices (chassis) long enough for the energy to seek a "safe"er path to ground....

Inductance and resistance....  BOTH need to be minimal in the path to earth ground so that the lightning event can pass through the system without creating too high of a ground potential difference anywhere and arcing/jumping from a "safe" place to a "dangerous"/damaging place.

Resistance can be reduced by shortening a conductor or merely making it BIGGER....  This reduces the "resistance" to change in voltage in the event...
INDUCTANCE opposes the increase in CURRENT through the conductor....  And as I understand it, inductance is reduced in a conductor by INCREASING the surface area of a conductor....  and the most reasonable way of doing THAT is by using wide, thinner conductors like straps....  typically COPPER straps as copper is the best compromise between lower cost and higher conductivity.

Thus, in summary.... the conductors you are using to bond everything together would IDEALLY be the widest copper strap you can route from place to place....  Strap/sheet copper is notoriously hard to route around corners, et al.... and this is ACTUALLY a good thing, because lightning does NOT like to turn corners....  The strap/sheet should be routed as close to a straight path as possible.... Where you MUST make direction changes, they should be as gradual as possible...  AND IF you must make a 90 degree change indirection over a short radius, you should consider engineering to do so with additional methods of reducing inductance in other ways. (soldering/brazing folds, et al).

I know this isn't totally correct and complete, but I think it's pretty close.

73,

______________________
Clay Autery, KY5G
(318) 518-1389
On 05/10/20 09:46, KE1F Lou wrote:
How would you measure that impedance? Between which two points?
Lou KE1F

On 5/10/2020 9:19 AM, john ni0k wrote:
John,

Have you measured the impedance of your ground connection? If the impedance isn't very low all the surge suppressors won't help you. Telcos and cell sites will do this and add to the ground system until it gets below 20 ohms. In some cases much lower than this.

73,
-de John NIØK

John Canfield wrote on 5/10/2020 8:08 AM:
I faithfully followed the grounding and bonding recommendations in the ARRL book. My entrance panel is by KF7P, every conductor (even the SteppIR 16 conductor control cable) that enters the shack is surge suppressed - both at the tower base and the shack entrance. The copper plate in the box is bonded to a ground rod which goes to another ground rod a few feet away and then on to the main AC load center ground rod and then up to the ground buss in that box. In the KF7P entrance box, a copper strap goes to a common ground buss in the shack. Every piece of equipment in the shack is connected directly to the common ground buss via braided wire.

My tower is 165' feet from the shack so there was no reason to bond the tower to the entrance panel. All coax is in one 3" conduit and all other wiring is in another 3" conduit.

I've put a lot of research and effort (and $$$) into lightning mitigation and I'm very happy with the results so far. We've taken some very close lightning strikes in the last few months.

Thanks to all for your tips and recommendations es 73 de John WB5THT

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