i just pulled new wire and coax up my mast. when i did the coax and disconnected the VHF mounting bracket i noticed that the ground for the VHF is not only grounded to the radio through the coax as it should be, but because the VHF antenna mounting bracket is stainless, and the screws that screw the bracket to the mast are stainless, the antenna/VHF are technically grounded to the mast also...which is of course grounded to my iron keel. (hunter 23' bolt on keel). now while water isn't much of a "Ground" and salt water is little better but still not a real ground, there is some conductivity. i wonder if this has any effect on the ground and or performance of my VHF. i could possibly remedy this with either nylon bolts through the VHF mount or possibly plastic, (or other non-conductive), mounting bracket. i backed it with rubber gasket material. tia~ william
VHF grounding question
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Good Question
Good question because this is possibly the ONLY point where your electrical system is connected to the mast, rigging, lifelines, pulpit, pushpit etc. If the shore power ground wire fails the whole boat could be lethal. Your mast is also likely to be bonded to your keel so the little anode, whilst trying to protect prop and shaft, now finds itself protecting keel as well. My boat is set up like this and I have always worried. Recently I tested the SWR on the antenna and it checked out almost perfect (1.1:1), so I would not expect any troubles in your setup either.
Good question because this is possibly the ONLY point where your electrical system is connected to the mast, rigging, lifelines, pulpit, pushpit etc. If the shore power ground wire fails the whole boat could be lethal. Your mast is also likely to be bonded to your keel so the little anode, whilst trying to protect prop and shaft, now finds itself protecting keel as well. My boat is set up like this and I have always worried. Recently I tested the SWR on the antenna and it checked out almost perfect (1.1:1), so I would not expect any troubles in your setup either.
VHF GROUNDING
The marine VHF frequencies are usually not a problem with your setup as far a ground is concerned. When you start using the Marine SSB which is a lower frequency in the HF band it requires a very good ground set up. If you check your antenna with a VSWR meter as Donalex suggested and it is between 1.5 and 1 you should not have any problems
The marine VHF frequencies are usually not a problem with your setup as far a ground is concerned. When you start using the Marine SSB which is a lower frequency in the HF band it requires a very good ground set up. If you check your antenna with a VSWR meter as Donalex suggested and it is between 1.5 and 1 you should not have any problems
Nylon HW not a good idea
Any non-conductive mounting will quickly fail and your VHF antenna will wind up getting whipped around on the top of your mast. Until it finally gets airborne. Antennas cost more than zincs.
Any non-conductive mounting will quickly fail and your VHF antenna will wind up getting whipped around on the top of your mast. Until it finally gets airborne. Antennas cost more than zincs.
I would check it with a multimeter
just to make sure you are not feeding DC into the bonding system and thereby causing electrolysis. If I had any doubt, I would insulate any DC on the coax (RF) ground from the bonding system. Other opinions may be different but I spent $4500 last year replacing the prop and shaft due to electrolysis so I plan to be much more careful. TV antennas are notorious for this so I would check that too if you have one.
just to make sure you are not feeding DC into the bonding system and thereby causing electrolysis. If I had any doubt, I would insulate any DC on the coax (RF) ground from the bonding system. Other opinions may be different but I spent $4500 last year replacing the prop and shaft due to electrolysis so I plan to be much more careful. TV antennas are notorious for this so I would check that too if you have one.
Where are the technocrats?
I always thought that VHF didn't need a 'ground'. The radio only needs to have both wires properly connected to the battery and no other connections. And the antenna is free standing, not grounded. And that the 'ground' on a ham/ssb set is really a counterpose to reflect the antennas radiated waves. But that's the limit of my knowledge. Or lack of knowledge.
I always thought that VHF didn't need a 'ground'. The radio only needs to have both wires properly connected to the battery and no other connections. And the antenna is free standing, not grounded. And that the 'ground' on a ham/ssb set is really a counterpose to reflect the antennas radiated waves. But that's the limit of my knowledge. Or lack of knowledge.
probably not a real problem in my case...
i dont have shore power so for all practical purposes water could mostly be treated as an insulator. "ground" is probably a misleading term in the case of my 12v only system and the VHF. ground = shield of the coax = neg batt terminal. (but this is also the issue since the neg batt terminal HAS to be at a different "potential" than the water) ..doesn't it? now if i burried my iron keel in soft, salty mud and tried to call for help this might be a little different story?? anyway, i guess its food for thought. my radio works so i guess i'll put an swr meter inline when the mast is raised and see what i will see. seems like these days of regulation "up the stern" if it were a potential safety hazard someone besides me would have thought of it by now...i better keep my mouth shut or i could find my mounting system REGULATED! thanks for the responses guys~ william
i dont have shore power so for all practical purposes water could mostly be treated as an insulator. "ground" is probably a misleading term in the case of my 12v only system and the VHF. ground = shield of the coax = neg batt terminal. (but this is also the issue since the neg batt terminal HAS to be at a different "potential" than the water) ..doesn't it? now if i burried my iron keel in soft, salty mud and tried to call for help this might be a little different story?? anyway, i guess its food for thought. my radio works so i guess i'll put an swr meter inline when the mast is raised and see what i will see. seems like these days of regulation "up the stern" if it were a potential safety hazard someone besides me would have thought of it by now...i better keep my mouth shut or i could find my mounting system REGULATED! thanks for the responses guys~ william
Your right Fred
On the vhf antennas it would be nice to have a metal plate under the antenna to act as the other half of the signal plane. However, vhf is considered line of site and you are not trying to use ionosphere reflections for distance.
On the vhf antennas it would be nice to have a metal plate under the antenna to act as the other half of the signal plane. However, vhf is considered line of site and you are not trying to use ionosphere reflections for distance.
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