Jedi VHF/AIS station design

[s/v Jedi]

I have new antennas and cables ready for installation so it was time to tackle this part of boat electronics for the final time.

This diagram is for a 24V boat. If you have 12V, simply swap the dc-dc converter from a 24/12-9 to a 12/12-9 model.

I will explain the diagram and describe how to use this.

The coax switch and Orion are installed in close proximity of the radio. If the coax between antenna and switch has a coupling at the mast (for pulling the mast) then I recommend you use a surge suppressor instead of coupler there as well. You can order the surge suppressor with female connectors at each end to make it plug compatible with a coupler piece, but don’t forget the bonding wire to the dynaplate.

The coax switch has one important feature: the unselected port is grounded. Make sure your switch does this; the Daiwa switch in the diagram does this but there are many clones so make sure by measuring with a multimeter. For the unselected port, the center conductor must be shorted to the outer conductor.

Normally you would attach a bonding wire to the metal housing of the switch. In this case the suppressor is directly connected to it and we combine switch and suppressor with one bonding wire. If you would leave out the suppressor () then make sure to have a bonding wire connected to the metal housing of the switch.

The DC surge suppressor is connected to the output of the dc-dc converter. It is assumed you already have a suppressor at the busbars of the power you feed to this Orion. If not then this is a good time to do this as well.

The Dynaplate is an underwater grounding plate. I recommend to connect the following and only the following parts to it:

- bonding wire from the base of the mast.
- bonding wire from each chainplate.
- SSB tuner ground lug (make sure the radio and tuner have an isolated power supply)
- ground wires from DC and AC surge suppressors.

- DO NOT- connect any AC ground or DC negative wires to this bonding plate.

-MAKE SURE- the bonding plate is rated for lightning protection.

What we have here is a simple and cheap coax surge suppressor on the incoming antenna coax cable. It is connected to one of the ports of the coax switch, while the other port has a dummy load rated for VHF frequencies and 25W minimum. The common port connects with a short coax jumper to the radio antenna connector.

Next is the power supply. The small 110W Victron isolated dc-dc converter does two things for us: it stabilizes the voltage and it galvanically isolates both the positive and negative conductors. It has a small potentiometer where you can set the output voltage: I recommend you set it at 13.8V.
On the input I show Anderson Powerpole connectors. I highly recommend you create a disconnect with these or even add another one between Orion and radio.

The VHF will come with a power cord that has an inline fuse; don’t remove the fuse and keep the cord long enough so that you can easily check/replace the fuse.

How to use this:

The coax surge suppressor has a gas charging arrestor element which connects the center conductor to the shield which is also the metal housing that has the bonding wire connected. When a surge occurs, the arrestor shorts it out to ground. Normally it will survive this and keep protecting, but in a bad hit it is a self sacrificing element that can be replaced (but is more expensive than the whole suppressor so just buy one extra).
You have this protection online all the time. I have been hit by lightning multiple times and the arrestor elements all survived it so far.

If you see a lightning storm approaching, you can take action to bring protection one step up by selecting the dummy load instead if antenna on the switch and turning the radio off. The coax switch will connect the antenna center conductor to ground via the bonding wire on the surge suppressor. Also, the radio has it’s antenna port connected to a 50 Ohm power resistor which prevents damage to the radio in case it transmits (AIS transponder transmissions) as well as provide termination of the otherwise open connector.

With the radio switched off, simply use a handheld VHF until the lightning storm passes.

If all coax protections fail and the radio internal protection fails too, then the Orion still isolates the radio from your main busbars to minimize chances of further damage.

[team karst]

Does your VHF SO235 connector internally bond with DC NEG?

[s/v Jedi]

Originally Posted by team karst

Does your VHF SO235 connector internally bond with DC NEG?

I have multiple VHF radios and I believe one does and one doesn’t. You need the isolated converter anyway so it doesn’t really matter.

Also, within a radio it is all a gamble on what will happen. Most radios have some internal protection but as you can guess this varies wildly and even when coax shield is isolated, a surge on DC power supply must be expected.

The wildest I have seen is a direct hit on the VHF antenna which evaporated, with many electronics items ruined but the radio itself still okay. This is a case of a well protected radio, i.e. this protects the radio itself, but nothing else.

[s/v Jedi]

The attached image is an export and it’s weird so I tried again and again until it was normal

[wholybee]

This is probably the best lightning protection I have seen. Maybe the only protection system that I would expect to actually work. Very nice and well thought out.

[S/V Illusion]

I have two Daiwa switches on which I’ve tested isolation. Although my knowledge is limited to these two, I found the isolation differs by -40dB.

You might want to ensure yours isn’t like my bad one.

[s/v Jedi]

Originally Posted by S/V Illusion

I have two Daiwa switches on which I’ve tested isolation. Although my knowledge is limited to these two, I found the isolation differs by -40dB.

You might want to ensure yours isn’t like my bad one.

What do you mean by “isolation”? These switches have so many knockoff’s… original are made in Japan.

[s/v Jedi]

Originally Posted by wholybee

This is probably the best lightning protection I have seen. Maybe the only protection system that I would expect to actually work. Very nice and well thought out.

Let’s hope it works well. I’m really trying to harden systems and it’s an extra $150 or so to do this, although half of that is the Orion which I need regardless.

It gets involved for boats that don’t have the bonding plate yet…

[Jammer]

In my experience the gas discharge arrestor is good enough that you don't need the switch. If you get a bad enough hit to burn up your radio behind the arrestor then the coax in the mast will be melted anyway and it won't matter whether or not your radio works.


I would omit the DC-DC and use a capacitor with a MOV bypass and a drain resistor at the dynaplate instead

[s/v Jedi]

Originally Posted by Jammer

In my experience the gas discharge arrestor is good enough that you don't need the switch. If you get a bad enough hit to burn up your radio behind the arrestor then the coax in the mast will be melted anyway and it won't matter whether or not your radio works.

I would omit the DC-DC and use a capacitor with a MOV bypass and a drain resistor at the dynaplate instead

It isn’t as much as protecting the radio but rather other electronics aboard. Using an isolated power supply is the industry norm and required anyway when you have a 24V supply for a 12V radio
Of course the surge suppression you describe is in the DC surge suppressor in the duagram.

The switch still adds protection because the arrestor doesn’t disconnect the center conductor from the radio like the switch does.

I used to remove the coax from my radio until I got half electrocuted from the charge hanging in the air and caught by my antenna. When I moved the coax plug center pin towards the radio, sparks jumped almost an inch

I have also experienced a radio with damaged output stage that was completely disconnected during a strike (my Kenwood 480 ) and I am convinced it was because of the open coax connector.
Edit: no, it was my Kenwood TM-D710

A year from now I’ll be able to report if it works because we’ll spend coming Nov-June in the Abacos lightning alley

[s/v Jedi]

BTW, I once had a lightning strike that evaporated half the antenna but left the cable completely intact. I still have that cable today, many years later and am replacing it simply because of it’s age.

[S/V Illusion]

Originally Posted by s/v Jedi

What do you mean by “isolation”? These switches have so many knockoff’s… original are made in Japan.

Isolation between ports (so as to not overload the inactive radio)

[s/v Jedi]

Originally Posted by S/V Illusion

Isolation between ports (so as to not overload the inactive radio)

Ah yes, I think that is caused by lack of internal shielding. The genuine one, at VHF frequency should have 60dB isolation.

[team karst]

Originally Posted by s/v Jedi

...
I used to remove the coax from my radio until I got half electrocuted from the charge hanging in the air and caught by my antenna. When I moved the coax plug center pin towards the radio, sparks jumped almost an inch
..:

eek; precipitation static. Was it raining or windy? or a bad black cloud nearby?

[s/v Jedi]

Originally Posted by team karst

eek; precipitation static. Was it raining or windy? or a bad black cloud nearby?

Lightning… which is why I removed it. But with no apparent strikes you still get high voltage there and my mast is only 20 meters high…