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Old 03-03-2016, 06:45   #1
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Icom m802 Rf grounding

Hi all
I know there has been alot brought up about icom m802 before, however I have one question I am hoping someone can clear up for me and would be much appreciated .
I am installing a m802 in my yacht and I know about grounding the Atu 140 to the ground plate by using the copper strap . However in the manual it says to also ground using the copper strap to the transceiver earth stud on the casing. The electronic tech I brought the equipment from says not needed as the connection to plate is done already via the atu 140 control cable and an addition strap would cause a loop and is not recommended.

Your thoughts

Cheers
Terry


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Old 03-03-2016, 12:03   #2
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Re: Icom m802 Rf grounding

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Originally Posted by Far Star View Post
Hi all
I know there has been alot brought up about icom m802 before, however I have one question I am hoping someone can clear up for me and would be much appreciated .
I am installing a m802 in my yacht and I know about grounding the Atu 140 to the ground plate by using the copper strap . However in the manual it says to also ground using the copper strap to the transceiver earth stud on the casing. The electronic tech I brought the equipment from says not needed as the connection to plate is done already via the atu 140 control cable and an addition strap would cause a loop and is not recommended.

Your thoughts

Cheers
Terry


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I have an 802 on a steel boat, when it was fitted “professionally (i.e very badly) ” in the UK, the ATU and the Black box were grounded to separate points using aluminium plates bolted to the hull

I then met another techie who had experience in Air Craft who suggested this could cause an earth loop so I grounded both to one point near the ATU

I later spoke to Bob Smith (the UK SSB guru) about the issue that DC current flows through the earth points EVEN THOUGH THE SET IS TURNED OFF!!!!

His view was that was the same as your electronic tech so I fitted a grounding isolation bridge to stop the DC flowing and changed it again to just grounding the ATU and all works really well.

The moral of the story is talk to many people and get many views.


Good luck
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Old 03-03-2016, 12:15   #3
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Re: Icom m802 Rf grounding

Terry-
The "facts" are that each device should make a straight direct run to a single grounding point, or failing that, to a common grounding bus which then goes to that single ground point.
If your radio goes to the tuner, and then the tuner goes to ground, yes, both devices are grounded and yes, in practice many people find this works perfectly well. But that does allow (and probably means) that your radio and your tuner may NOT be at the exact same ground potential, so depending on circumstances doing things the easy way (daisy chaining the radio and tuner to the ground) MAY be perfectly good enough, but it will NOT be the "proper" way to ground the radio.


Unless it is terribly inconvenient or expensive, I'd run short straight direct grounds from each device, directly to the RF ground point. (Which of course is not your lightning ground point.) You know, why take a chance, when you can so easily make sure you're "up to code" so to speak and doing it in accord with best practice?
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Old 03-03-2016, 12:21   #4
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Re: Icom m802 Rf grounding

Terry,

The techie you spoke to was correct: ground the AT140 tuner ONLY. No RF ground needed at the main transceiver box, and it could well cause a ground loop.

Bill
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Old 03-03-2016, 13:29   #5
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Re: Icom m802 Rf grounding

Bill-
http://icom.custhelp.com/ci/fattach/...ion+Manual.pdf
The ICOM manual shows the radio and tuner being connected, and then that one common point--not a daisy chain--connected to ground. That would be effectively, using a small ground bus (the connection point) and a direct single ground run.
Definitely not a daisy chain, per ICOM and per ARRL policy on best practices.


FWIW.
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Old 03-03-2016, 14:47   #6
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Re: Icom m802 Rf grounding

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Bill-
http://icom.custhelp.com/ci/fattach/...ion+Manual.pdf
The ICOM manual shows the radio and tuner being connected, and then that one common point--not a daisy chain--connected to ground. That would be effectively, using a small ground bus (the connection point) and a direct single ground run.
Definitely not a daisy chain, per ICOM and per ARRL policy on best practices.


FWIW.
Yep, and the manual is misleading. The transceiver box and the tuner should be connected ONLY by the control cable, with ground connection in that cable connected only at one end, and by the coax.

Additional connections will often cause problems.

Sorry, but this comes from real-world practices on many boats with the 802.

BTW, Instruction Manuals are often misleading or dead wrong....even for quality manufacturers and good equipment. It would be interesting sometime to probe the causality of these disconnects....Imperfect or poor understanding of RF principles? Lawyers? Sales staff? Parroting "best practices" from some publications? Repeating the perennial errors (like the 100sq ft of metal needed for an RF ground)? Who knows? Buyer beware :-)

Bill
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Old 03-03-2016, 15:49   #7
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Re: Icom m802 Rf grounding

and here I always thought the tuner and the transceiver were connected by the shield on the coax cable, not the control cable....
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Old 03-03-2016, 16:48   #8
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Re: Icom m802 Rf grounding

Thanks for all the replies guys, much appreciated. Ñow I know why there are so many SSB threads. Can I change this question around now. What happens if you don't ground the transceiver unit directly, what is the direct grounding suppose to do ?
Cheers
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Old 03-03-2016, 20:18   #9
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Re: Icom m802 Rf grounding

Bill (WA6CCA) is one of the real experts on this; as he noted, Icom's manual is just plain wrong in several areas as are many out there.

There is no reason to ground the transceiver and it may cause problems. The coax shield of the radio to the tuner and the wiring between the head and the transmitter keep all three at the same potential. If you have your RF 'capacitance ground / counterpoise / direct seawater connection / or whatever you want to call it' attached to the tuner you are avoiding any possible 'ground loop' that can make tuning difficult and provide a return route for stray RF.

There really isn't much magic to this, the military and hams have HR radio pretty much figured out; just follow their lead and you'll be fine.
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Old 03-03-2016, 21:38   #10
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Re: Icom m802 Rf grounding

Watching this thread with interest as I am doing the same installation.

Some related questions: The Icom grounding guide (linked to above) also recommends putting in a DC block on the ground strap (four 15 microfarad capacitors in parallel).

- Is this useful/necessary?
- If yes, where should the block be best installed? Close to tuner, or does it not matter?
- The DC block they picture seems like a fragile design. Any concerns/issues if encapsulated in epoxy?

Thanks in advance.
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Old 03-03-2016, 22:40   #11
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Re: Icom m802 Rf grounding

This is the info I have on DC Block
I was told to make sure I install see drawing attached.

Grounding Isolation Bridge (1000 pF 15000 volts ground isolation > 100k ohms)

A grounding isolation bridge is required to stop or reduce electrolysis on boats that have a negative DC supply, e.g negative is not connected to salt water. The bridge blocks DC curents going to salt water via the ground plate

Installation

The bridge goes between the ground bolt on the bottom of the ATU (antenna tuner) and the copper grounding strap. Ensure that no other contact is made to the copper strap or the grounding plate(s)


Cheers
Terry


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Old 04-03-2016, 12:12   #12
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Re: Icom m802 Rf grounding

Damn, I spent four hours last weekend grounding the tranceiver after running ground strap and soldering it to the AT ground like the manual said, oh well it is easy to disconnect if need be.
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Old 04-03-2016, 16:15   #13
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Re: Icom m802 Rf grounding

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Originally Posted by btrayfors View Post
Terry,

The techie you spoke to was correct: ground the AT140 tuner ONLY. No RF ground needed at the main transceiver box, and it could well cause a ground loop.

Bill
WA6CCA
Bill,
What would you consider to be the better method, grounding the AT140 directly, and separately, to a nearby bronze though-hull via 6-7 feet of 3" x .030" copper strap, or grounding the AT140 to the factory installed, glassed in, hull ground plane, that is made up of connected copper straps all throughout the hull? This ground plane has various connections to other stuff ( such as chainplates, and other assorted ground connections ), though.
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Old 04-03-2016, 17:43   #14
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Re: Icom m802 Rf grounding

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Bill,
What would you consider to be the better method, grounding the AT140 directly, and separately, to a nearby bronze though-hull via 6-7 feet of 3" x .030" copper strap, or grounding the AT140 to the factory installed, glassed in, hull ground plane, that is made up of connected copper straps all throughout the hull? This ground plane has various connections to other stuff ( such as chainplates, and other assorted ground connections ), though.
I know you're asking Bill, but my PSC44 has the same glassed-in ground system as your boat and my tuner is grounded to the ground strap in the aft locker (where the tuner is, near the backstay antenna). The radio works very well indeed. I've been the communications boat for the last four Pacific Cup races and make a lot of SSB contacts. Our signal is always one of the best. Anecdotal evidence I know, but it works for me.
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Old 04-03-2016, 18:01   #15
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Re: Icom m802 Rf grounding

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I know you're asking Bill, but my PSC44 has the same glassed-in ground system as your boat and my tuner is grounded to the ground strap in the aft locker (where the tuner is, near the backstay antenna). The radio works very well indeed. I've been the communications boat for the last four Pacific Cup races and make a lot of SSB contacts. Our signal is always one of the best. Anecdotal evidence I know, but it works for me.
Thanks, Paul.
I was thinking about the effect that the various other connections made to the factory installed ground plane might have on the SSB/HF system. I'm sure your installation is very similar to mine, which has numerous other ground connections to the ground plane. Things like the port and stbd. chainplates, the DC ground buss at the distribution panel ( parallel to the battery negative ) and, also, the ground plate located out side, on the hull. I was wondering if these other ground connections negatively (pun intended) affected the SSB/HF operation.
My tuner would be in a similar location to yours, within a few feet of the backstay antenna, and right at the connection point to the ground plane.
Thanks again for taking the time to share your experience.
Bill Petras
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