"BIG FUSES" or RF SURGE PROTECTION
Panama City
October 20, 2012
With my captain away, I have nothing better to do than catching up on my writing. Yes, I’m way behind, still reeling from the havoc of the lightning strike. What have we learned? How did we make the boat better?
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| Not an easy position: surge suppression on the Glendinning control head. |
I sent out a marine lightning survey to cruisers. I am amazed to learn that although all are worried about lightning, cowering under the pillows during a storm, very few are actually doing something to protect their boat and equipment beyond tossing a handled VHF and GPS in the oven. We think there is much more that can be done. For example, protecting the equipment from electrical and RF surges.
In a previous blog, I have explained about “little fuses” or transient surge suppressors (TVS diodes) to protect the AC and DC electrical circuits and equipment. As an example, I posted pictures of our engine protection system. JP installed some 20 of those diodes on all the equipment, and I’m posting here pictures of some of the in-line applications.
1) In-line TVS diode - Twisting the wires reduce the magnetic field between the wires.
2) TVS diode on shielded wire - Adding foil as a shield.But how to protect your VHF, AM/FM, AIS, and SSB from RF surges? Coax cables demand another kind of protection. For this, we turned to The Protection Groupagain and their line of POLYPHASER gas capsules. I’m not a tecchie, so I’m not going to launch into an explanation of how the stuff works. There is plenty of info on the Protection Group site. It goes without saying that what is good enough for all the large cell phone towers, ships, locomotives, is good enough for me. But how do you choose the right RF protection for your application? DC block or DC pass?
To choose our arrestors, we turned to our manufacture techs as well as the TESSCOtech support. This is what we have chosen, based on frequency range, throughput energy, connectors and maximum power frequency.
Bulkhead-mounted Polyphaser - N-connectors, N-male and N-Female (if we need to remove the Polyphaser, we can always connect the M/F ends); Note the grounding and the coax cable loop. Mounted at the base of the antenna.
For our ICOM 718 radio, we are still in the process of selecting a product. These are the recommendations from ICOM:
“ A Polyphaser could be installed between the 718 and the tuner. DC Block would be fine.
- I would also look for a "control Line" Polyphaser unit for rotor control cables as this could be used on the tuner control line. It would need to be a DC pass device.
- The antenna side of the tuner does not have a lightning protection device available.”
- I would also look for a "control Line" Polyphaser unit for rotor control cables as this could be used on the tuner control line. It would need to be a DC pass device.
- The antenna side of the tuner does not have a lightning protection device available.”
In other words, there is no way to protect the tuner.
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| Connecting the coax cable to the N-terminal |
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| Making sure that the connection is proper: no short |
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| Connecting the surge protector to ground |
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| Using KOPR-SHIELD to enhance connection |
We take lightning seriously. While doing the survey, I’ve read horror stories of boats being blown to pieces (40 holes in the hull), being struck 3 times, losing all power and electronics. When at anchor, we still disconnect most of our electronics. But, being a powerboat, we can’t do that while underway, and I certainly would not have disconnected the AIS last month when a sudden T-storm surprised us while transiting Colon Harbor, one of the busiest ports in the world: we couldn’t see 100 yards outside but the AIS showed us surrounded by boats. Lightning or not, we had to rely on our radar and AIS. Unplugging the equipment at every sign of lightning is NOT a viable option, not for us, not while underway.
So, I’ll let the pictures do the rest of the talking, while I visit with my neighbors at anchor, all hit by lightning within the last 3 months: “Samara II” in Portobelo, “Eyes of the World” in Las Perlas, and “My Muse” in Belize. FYI, that’s one monohull and 2 catamarans.
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| JP can't gain weight! He needs to get into all those tight places. Here, under the "Kepi" to reach the base of the antennas |
Until next time....
dominomarie
