[Amel Yacht Owners] Re: Icom M802 and AT140 tuner grounding
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Alan is 100% correct. I spent hours (okay ~ days ~ or, perhaps weeks) researching this. The 802 cable that connects the 802 to the AT has a ground wire and should be connected to both the 802 and to the ground on the AT which in turn is connected to the copper strap in the lazarette. There is no connection to the ships common ground (yellow and green wiring system) .
I installed an isolated 24-12 power supply. Although this has a ground connection available, I was told not to connect it. Only the battery cables are connected to the isolated 24-12 power supply.
Hope this helps.
Best regards,
Mark Skipper Sailing Yacht Cream Puff
From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Friday, June 06, 2014 6:37 PM To: amelyachtowners@... Subject: [Amel Yacht Owners] Re: Icom M802 and AT140 tuner grounding
Amel say don't connect the SSB ground to the ships earth...
The 802 ground should be connected to the tuner ground and that connected to the copper strap in the lazarette only.
If you don't have an isolated 24 - 12v supply for the SSB, you need some way of isolating the negative supply of the SSB when not in use...at least for the 710, where the negative power line in the SSB is connected internally to the earth.
I posted a simple way of doing this that completely isolates the SSB when you turn the breaker off.
If you don't do this the negative supply will have a low current connection to ships ground through the seawater.
Hope this helps Cheers Alan SV Elyse SM437 Papeete |
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Herbert Lackner
If you want to be on the safe side you can put 10 small ceramic capacitors with 3900pF (2500V) each, solded together in parallel (will give 39nF(2500 V) with little Skin Effect) between the tuner ground (ssb ground) and the boat ground. This will prevent any DC current (and will prevent electrolysis) but will give a solid HF AC connection. Herbert KALI MERA, SN 120 Kusadasi
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Herbert,
This just went way over my head. If the capacitors are on parallel this means 4 connection points – two at each end? How is this connected to the single ground wire? Also, the boat ground is not used?
Best regards,
Mark
SM2K #275
From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Friday, June 06, 2014 7:08 PM To: amelyachtowners@... Subject: Re: [Amel Yacht Owners] Re: Icom M802 and AT140 tuner grounding
If you want to be on the safe side you can put 10 small ceramic capacitors with 3900pF (2500V) each, solded together in parallel (will give 39nF(2500 V) with little Skin Effect) between the tuner ground (ssb ground) and the boat ground. This will prevent any DC current (and will prevent electrolysis) but will give a solid HF AC connection.
Herbert KALI MERA, SN 120 Kusadasi
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I think Herbert means that you can use the ships earth to make your SSB ground even better, as long as you isolate any DC current from it and you can do that by wiring 10 3900pf capacitors in parallel between the SSB ground and the ships earth - you actually have 20 connection points, 2 for each capacitor ! - the capacitors will conduct Hi frequency AC (your radio signal) but block any DC component. But you still don't connect your 802 ground connection to ships ground. And you still need an isolated power supply, or use the relay system I posted to keep the DC off the SSB ground...other wise that will come back through the seawater to your ships ground. OR Capacitors can also be used in the SSB ground with the same effect, to keep DC current from entering the seawater.....break the SSB ground connection after the tuner...between the tuner and the SSB ground plates.....best place is the copper foil....cut it across so there is no connection, and then solder 10 of those caps across the gap, side by side (ie in parallel) Cheers Alan SV Elyse SM 437, Papeete |
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Herbert Lackner
Good Morning to all, Alans 2nd option was what I wanted to explain :-) On our SN we do not have a separate HF ground (I think this was an option that the first owner did not order from amel), the copper foil is connected to the yellow green line and therefore to the rudder.... Maybe all SMs have the the separate HF ground? So to prevent any grounding problems I choose the solution to put the capacitors in between the tuner ground and the copper foil (in serial, that means that there is no DC connection between the tuner ground and the copper foil, the capacitors will block any DC currents but will let HF through). The SSB itself will not be grounded in a normal installation. Sometimes it has to be grounded, when problems (like HF burn when touching the SSB during transmitting, you will find out if you have these problems ;-) ) occur, and then you should also use the capacitors (serial) when connection the ssb ground. Before you do that you should check your ssb installation to eliminate other reasons for these ssb problems before you ground the ssb (this is in my opinion only the last option). In some SSB installation manuals you can read that the ground has to be connected but this is normally not true on a sailboat, It is true on a standard land based installation in the shack at home. in my Kennwood the -12V that goes to the SSB (from the battery, we have a 12v system) is directly connected to the Coax antenna shield that goes to the tuner, therefore blocking DC current at the tuner ground is absolute necessary to avoid to have a dorect connection from the battery to the Amel grounding system. The capacitors are solded together in parallel so that it is like one big capacitor with two legs, it is installed as a blocking element in serial (cut the old cable and put the element in between). Hope that makes it more clear what I tried to say Herbert KALI MERA, SN 120 Kusadasi
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very good explanation Herbert I think that all SMs have the two seperate grounds....in mine it was written on the cables at the nav station...so it should be clear which ground is which... Cheers Alan SV Elyse SM437, Papeete |
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Ian Park
Herbert,
I agree. I have been searching for a second ground in the bilge on my Santorin, and there isn't one there - just the copper strap in the lazarette. Thanks for your information on grounding the tuner. I am a novice with SSB and before I start using it I will check the ground system and fit the capacitors. Thanks for the details. My electronics knowledge is at a very early learning stage. We're heading south from UK at present, heading for Cape Verde. Best wishes Ian and Linda. SN 69. Ocean Hobo |
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islandbwoy4434
Thank you to the group for clearing up my confusion.
Terry SV Libby |
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islandbwoy4434
Alan/Mark, I acknowledge that the manufactured cable that connects the 802 to the AT140 has a ground wire in it. It is a bare wire, correct?
Here is what I understand, please correct me if I am wrong. 1. Connect the ground screw of the IC802 transceiver housing to the bare ground wire. 2. Connect the bare ground wire on the other end to the AT140 tuner ground terminal which is also connected to the copper grounding foil in the Lazzarette. Power to the system is isolated, so no need for the DC blocking capacitors. |
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Yes, it is connected to the points you mention. However, the cable I have with my unit, the green ground wire is insulated (not bare).
Mark sm2k #275 On Thu, Jun 26, 2014 at 9:32 AM, terencesingh@... [amelyachtowners] <amelyachtowners@...> wrote:
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Basically yes, shouldn't be a bare wire though..yellow with a green stripe, as big a gauge as you can deal with and write on it "SSB" ....
Good luck, Cheers Alan SV Elyse SM437 Papeete |
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