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Hi,
Key to grounding is to ensure everything is at the same potential. There will be zero current between two wires that are at the same voltage. No current, no damage.
If you ground the AC surge protector which uses MOVs to connect all it’s wires together and to ground, the antenna shield with a coaxial surge protector to connect the center conductor to ground, and if used, all 8 of the rotator control line to the same ground with MOVs and possibly GDTs then everything is at the same potential during a strike.
This is extended to the radio and computer by grounding their cases together and to the common station ground. This process of tying everything together is called bonding.
If this is all there is the equipment would survive a 2KA spike. Note that even a strike on the power grid, which is likely, will appear on the AC surge protector at the station ground and via all of the MOVs and GDTs will result is a equal potential on all of the lines, including the antenna and rotator.
Where the damage occurs is when paths outside of the “bonding” are introduced.
As an example everything is bonded except the computer or monitors are plugged into a wall plug and not the station surge protector. There is a USB cable between the PC and radio. During a strike on the antenna the radio will be at many KVs, the PC grounded back at the service entrance will be near zero V. The potential difference will be across the USB cable and the current through PC/radio circuits. The same is true if the strike is on the power grid and the current is flowing to the station ground.
<p style=”text-align: left;”>Lightning has a broad RF spectrum. A larger conductor will have more surface area to reduce skin effect and will have a lower inductance.</p>
The ground wire 60′ across the basement to the service panel isn’t directly part of station bonding. The strike will be over before the service panel end of the wire will reach its peak voltage. It will help to mitigate the damage to everything outside the operating position and provide protection from AC ground faults.I see a radio every few weeks with lightning damage. Damage to USB devices is most common, the DC power input circuit is second, both likely due to power line strikes. The RF input is last, but typically has the most visible damage with missing parts, melted relays, and burnt traces.
The take away is to eliminate potential voltage differences and to watch for stray paths, this includes the desk lamp next to the radio.
I ran across this article on grounding and bonding last week as I was searching the net for information on article 810 in the NEC. It might be helpful to some folks.
https://pslara.org/docs/2.D.pdf
Technical Problem with RG8X Coaxial Cable Connector Pins.
I am finishing up my home ham radio station and trying to install a lightning surge protector between the J-pole antenna feed and the line going to a window pass through to the transceiver.
When attempting to install the surge protector, I noticed that the cable center connectors were splitting apart the small copper host in the protector due to the connector angle (sloped) in the cables. So, I used a file, sand paper, and polishing cloth to flatten the center connector to help mating with the surge protector copper host. Unfortunately, with this action I have lost signal connectivity.
I was using a HT radio to check signal connectivity with the coaxial cables and J-pole before undertaking the connector modification. Local NWS weather signal was received load and clear. Now, I do not receive this same signal with / without the lightning surge protector. In the latter case, I used a simple Female-Female connector to receive the two cable connectors.
So, my questions are why cannot the cable center connector geometry be adjusted to “mate” with the lighting surge protector in the manner used? How can the signal transmission problem in the cable connectors be corrected?
Note that no other changes have been made to the radio configuration, so the issue resides with the connectors. HT radio functionality has been checked by directly connecting to the J-pole too.
Thank you,
John Wagner, KN4OMB
I don’t know how to answer the question about modifying the center pin. But, I can comment on grounding and protection strategy.
The J-Pole antenna has the center conductor connected to the ground through a quarter wave shorted stub. At the frequencies of lightning and static discharge (KHz and low MHz), the J-Pole shorts the coax center to shield. There is little benefit for a coaxial surge protector type device.
The risk to a radio is from the lightning surge current on the _outside_ of the coax conducting _through_ the radio and power supply to the power line or computer equipment connected to the radio.
Most of the protection from a coax surge protector comes from grounding the device near the station ground, assuming the radios and other equipment are also grounded.
The best approach is to surge protect the power lines and connect the green wire ground to the coax shield so the current has a better path _around_ the radio rather than through it.
My cheap low power solution is to get a surge protected power strip with two F connectors. Then loop the coax from the radio to power strip then to antenna. I have used this successfully at 100W on HF and at 50W on VHF. Also plug any computer or audio equipment into the same outlet strip.
Yes there is a mismatch between the 50 Ohm radio and the 75 Ohm F connections, but the length of the 75 ohm portion is short compared to 2 meters so adds little SWR to the system.
Also, internet connections are a big risk because they connect to long external wires. I use WiFi or Ethernet over fiber to isolate the shack computers from the wired internet.
jeff, wa1hco
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