Current RF Grounding methods/requirements

Wiring your boat, How to Wire Lights/Accessories, All things electrical other than actually powering your boat by electric motors.

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PaulM
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Current RF Grounding methods/requirements

Postby PaulM » Sun Jul 16, 2017 3:15 pm

Long time Forum Member/lurker/learner here. Nine year building of a Glen-L Escort with a modified pilot house from the Hunky Dory pilot house assortment. Built the outboard Escort version with an Armstrong engine platform on the stern. Now has a 200HP Yamaha 4 stroke on her stern.
I've been helping an un-handy owner with this project a long time now, and we can see light at the end of this particular tunnel. I myself have built 4 boats and restored 5 mahogany woodies. On this build, the owner has insisted that the hull have NO thru-hull openings at all. The owner is advocating a very spartan onboard lifestyle and it will be used primarily as a day tripper to start with. And so it is. Also this is a trailered boat.
AYBC compliant wiring is about 80% done and now the business of Vhf radio, chart plotter, hailer and possibly low energy Broadband radar are being asked. We.ve got lots of Blue Sea circuit and device protections through out including Yamaha controls and generation,and a small but proper AC shore power system with galvanic Isolation on the safety ground. The A/C green safety ground wiring is cross connected at one point only to the DC negative
buss near the battery.All tests fine at this point.
My question Is: Do modern electronic devices require an Isolated (not sure if that is the correct term) "RF" grounding system to work properly. We have no thru-hull fittings to bond to and the only water born device is the lower unit of the Yamaha. Is this sufficient ? ? I have read many of the publications out there and they seem to be somewhat outdated and primarily pointed at inboard power and/or sailboats.
Any thoughts or insite here will be very much appreciated from this old boathead.
Keep the tools sharp!
Paul

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steveh41
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Re: Current RF Grounding methods/requirements

Postby steveh41 » Sun Jul 16, 2017 3:32 pm

Paul,

The VHF radio and Broadband radar should have a solid RF ground, but it's not as demanding as the one required for the old SSB radios (not sure if anyone is installing these anymore). Don't know the particulars of your outboard grounding setup but I'm guessing it should be adequate. You might get a local marine electronics tech to check it out. Installing an underwater ground plate, if necessary, really doesn't have the immediate risks inherent with a through hull.

Here's an article to check out:

https://www.marineelectronicsjournal.co ... =VIEW&a=34

Regards,

Steve
The longest journey begins with a single step… then repeat as necessary!

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kens
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Re: Current RF Grounding methods/requirements

Postby kens » Sun Jul 16, 2017 4:10 pm

At the end of the day, there is only ONE ground.
AC ground, DC ground, RF ground, shielded ground, chassis ground, eventually it is all the same.
Look at the diagram in the above posted link, all the different ground plates, or ground terminals, all eventually end up at the motor block, or main batteries.
Sooner or later, it all ends up being the SAME ground.
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

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steveh41
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Re: Current RF Grounding methods/requirements

Postby steveh41 » Tue Jul 18, 2017 7:50 am

Ken,

I agree with you regarding all ground points being theoretically at the same potential, but this is only true if there is no current flowing in the DC ground circuits (black lines in the diagram included with the article). As soon as current begins to flow the different ground nodes will change slightly due to voltage drop along the associated current paths; this may be just a few millivolts but still significant as noise for sensitive equipment such as radios. The RF ground and other bonding circuits (green lines in diagram) are effectively non-current carrying and therefore "cleaner" than the other DC ground points.

Steve
The longest journey begins with a single step… then repeat as necessary!


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