Mystery Mast Bonding in E35-2

[WindHorse]

In the process of trying to track down an RF issues (receiving adjacent channel interference on my fancy new VHF), I determined that my mast is not connected to DC ground (not continuity, at least). However, with the coax disconnected from both the antenna AND the radio, I read 12v (with digital multimeter) between the coax shield (black to shield; red to batt). Again, this is with a totally disconnected coax cable on both ends. When I disconnected the ground DC ground connection to the engine/prop, the circuit was broken. This tells me two things: 1) the coax is somehow (intentionally or not) bonded with the mast, and, 2)The circuit for the 12v reading included coax to mast (possibly a "grounded" connector at base of mast), a MYSTERIOUS connection between the mast and the seawater, and back through the prop shaft/engine.

Does anyone know if the 35-2 masts/deck steps were somehow bonded for lightening or RF protection??? I cannot seem to identify any straps/wires from any of the chain plates or mast wiring (FYI, I disconnected the DC ground wire to mast electronics for this test), and yet something other than the DC ground circuit is allowing 12v to flow between the mast and the battery.

Incidentally, I found that I could eliminate the VHF interference issue by simply grounding a chain plate to the DC ground...but I've read that it's best for the mast to be independently grounded to water--and not through the DC ground system... I can obviously get to the bottom of this by hauling out and taking down the mast, but I'd rather know what's going on first.

Any and all ideas, experience, and advice appreciated!

 

[steven]

On my e35-2 there is nothing I can find that looks like a mast ground.

 

[Loren Beach]

Data point: My California-built EY boat has no mast connection to ground. OTOH, our previous Niagara (by Hinterhoeller Yachts) did -- but it was built in Ontario CN, so lightning might be more of a concern there.

 

[Dave G.]

There must be another ground circuit(wire) going into the mast that is tied into the engine ground somewhere. Don't think there is another possible explanation ?

 

[steven]

I thought maybe the shrouds are bonded. But I cannot find any evidence of that.

Its possible there is a grounding wire inside the compression post that goes to the bottom of the compression post (where there might be a steel shoe) and than to something in contact with the sea. Next time I'm aboard I'll try to get a camera in there from the bilge.

 

[DaveE26]

I grounded my mast shrouds and rudder stock to a 12X12 copper plate on my hull I also grounded the life lines and pulpits. I then grounded all the thru hulls to the plate as well. I hate lighting now! I am in fresh water so the plate should be twice as big but I have plans of going south.

 

[WindHorse]

There must be another ground circuit(wire) going into the mast that is tied into the engine ground somewhere. Don't think there is another possible explanation ?

Agreed. For the life of me, I just can't find it. It looks like I will be taking down the rig on the next haulout, as I have to deal with the coax short in any case...

 

[Farlander]

On my mast there is a common ground that serves all the lights on the mast. It's possible that somewhere inside the mast conduit, or outside the conduit if that's the case, chafe may have caused the main negative for the lights and the antenna coax ground to get together.

The definite solution would be to install a Shakespeare antenna on the transom or stern rail and just ditch the old antenna wire for now. I got a 6 footer on the transom that will definitely work even if the mast comes down, and I have a handheld HX890 which I keep attached to me when soloing. Eventually I'll have a mast head antenna too that will be the primary, and the shakespeare will be easy to plug in if I lose the rig.

I would suggest check your volt meter is set to the right mode, check with a different meter, verify antenna wire disconnected at both ends, and check the cable again. If you are truly getting 12V on your coax between batt+ and coax grounding shield, it's probable the main ground for mast lights has chafed and is contacting your antenna cable. See if turning mast lights on/off makes static change pitch.

 

[WindHorse]

On my mast there is a common ground that serves all the lights on the mast. It's possible that somewhere inside the mast conduit, or outside the conduit if that's the case, chafe may have caused the main negative for the lights and the antenna coax ground to get together.

The definite solution would be to install a Shakespeare antenna on the transom or stern rail and just ditch the old antenna wire for now. I got a 6 footer on the transom that will definitely work even if the mast comes down, and I have a handheld HX890 which I keep attached to me when soloing. Eventually I'll have a mast head antenna too that will be the primary, and the shakespeare will be easy to plug in if I lose the rig.

I would suggest check your volt meter is set to the right mode, check with a different meter, verify antenna wire disconnected at both ends, and check the cable again. If you are truly getting 12V on your coax between batt+ and coax grounding shield, it's probable the main ground for mast lights has chafed and is contacting your antenna cable. See if turning mast lights on/off makes static change pitch.

I actually disconnected all the wiring from the mast as I tried to chase down the problem--and, to be clear, I do not get continuity between the mast and DC ground...thus, the only pathway is through the water (unless there is a mysterious connection to the engine block that I didn't isolate)