Re: [Amel] Isolated or non Isolated DC to DC Convertor

Herbert Lackner

Hi Attilio,


Thx for the information, I will try the KISS-SSB, the Tuner will be mounted at the same point as you have it. If the KISS-SSB is enough grounding then I will not connect it to the rudder, but will check how it works.


I will install the SCS pactor 3 modem and will isolate the backstay when Lorenzo changes the rigging in spring.


My Call-Sign is  OE3HLA


Fair winds



SN #120, Kali Mera, Croatia





Von: amelyachtowners@... [mailto:amelyachtowners@...] Im Auftrag von Siviero Attilio
Gesendet: Freitag, 29. November 2013 19:10
An: Briggs Craig
Betreff: Re: [Amel] Isolated or non Isolated DC to DC Convertor





I Installed on my Santorin #84 "Sisila" an Icom 718 with an Icom AT141 automatic tuner and Pactor modem, and it works well with a KISS-SSB couterpoise to act as ground plane (see, it costs 125€ including shipment). My "techie", an ham radio expert much more than me, also connected the ground to the rudder, as you think to do.


The advantage to have the kiss-ssb is that you have a ground plane also out of water, when you are on the hard, and the ground plane is more "consistent".


The antenna is an insulated backstay, some 10m between insulators - very expensive piece of shroud, some 500€  -,  it acts as a lambda/4 whip antenna, which with the ground plane works as a lambda/2 dipole antenna 20m long, perfect fro 40m band without any tuning, and also for 20m band, the most crowded by ham radio enthusiasts and short-wave listeners (SWLs), so when you navigate you have always somebody ready to listen to you.


Your rig seems to be better than mine, at least more powerful, and also the tuner is OK, but be careful to place the tuner as close as possible to the antenna, otherwise you tune the feeding line more than the antenna. Mauro put it in the lazarete, just below the antenna, and the KISS-SSB runs around the lazarete ceiling, just around the top opening.


The tuner permits you to use the antenna also for 80m and 160m, the low bands most used at night, with the Pactor I was able to do emails from everywhere, via Winlink.


My American call-sign is KD2ECB, General Class; the italian one is in course of assignment, Extra Class, in the next months (italian bureaucracy is back in middle-age time....).


Hope this helps, fai winds



Attilio & Maria Siviero 
Amel Santorin#84 "Sisila"


Il giorno 29/nov/2013, alle ore 18:21, Herbert Lackner <herbert@...> ha scritto:



We will install a Kenwood 480HX SSB with an MFJ 993BRT automatic antenna tuner on our SN #120. We do not have a HF ground plate (I think that was an only an option for the SN). To ground the antenna Tuner I planned to connect it to the rudder shaft where the thick yellow/green cables are connected (I assume they are for the VHF grounding).


is that ok?  (do not want to have a   Swiss cheese rudder shaft J )


Thanks, Herbert

SN #120 Kali Mera, Sukosan



Von: amelyachtowners@... [mailto:amelyachtowners@...] Im Auftrag von Joel F Potter
Gesendet: Freitag, 29. November 2013 17:16
An: amelyachtowners@...
Betreff: RE: [Amel] Isolated or non Isolated DC to DC Convertor



All Amel boats since at least as far  back as the Meltem in the 1970’s has a floating/full earth return 12 and/or 24 volt direct current system. Simply, this means all DC power comes out of the battery, to the device that needs the power, AND THEN RETURN COMPLETRLY AND DIRECTLY TO TH BATTERY BANK. This prevents many possibilities of corrosion and keeps noisy things like fans and fridge motors from ‘talking’ to your radio, stereo and so forth. It is extremely important to never corrupt this system as, depending on how much power has been corrupted, you can suffer serious problems with electrolysis and feedback.


All Amel’s that had a ICOM SSB installed at the shipyard came with a special ICOM 24-12 volt transformer/converter with an isolated negative to accommodate the floating/full earth return. If you provided your own equipment for them to install, they always insisted on the special isolated negative transformer and would not install transformers that were not compliant with this. SSB’s require a healthy amount of power that can cause trouble if not integrated into the DC system correctly.


If your Amel has been modified by those unknowing of the type of DC system it has, change it back to the way God and Captain Amel ( and Jacques Carteau! ) conceived it.


If an electrician or electronics installer comes to your boat, be sure to ask him if he is familiar with a floating DC systems. His answer should be in the affirmative with a compliment that this is the best way to power DC gear. If he says “no”, “that’s stupid”, or “Whuzzat”, send him away. Trust me, you don’t want to screw around with this. I sold a SM 53 boat where the rudder shaft was Swiss cheese because of an improper SSB install. When we dropped the rudder to replace it, I bent the shaft in half with my bare hands. They guy who bought this boat still owns it, I believe, and I invite you to chime in here. He spent $3500 to repair the wiring and more to replace the rudder shaft here in Fort Lauderdale. Amel was a big help with technical assistance but Carteau admonished me to not screw around with the DC electrical system even though it wasn’t I who ever messed with any DC system on an Amel.    


All the best,




Joel F. Potter - Cruising Yacht Specialist, LLC

Amel's Sole Associate for the Americas

Mailing Address:  401 East Las Olas Boulevard #130-126

Fort Lauderdale, Florida  33301

Phone:  (954) 462-5869   Cell:  (954) 812-2485

Email:  jfpottercys@...



From: amelyachtowners@... [mailto:amelyachtowners@...] On Behalf Of Richard03801
Sent: Friday, November 29, 2013 10:27 AM
To: amelyachtowners@...
Subject: Re: [Amel] Isolated or non Isolated DC to DC Convertor



Hi. Under the navigation station the doors on the right side have 12 V power supplies that should be your source for 12 V coming off the 24 bank. I believe the brand name is sailor. 

In the ass locker there should be a copper foil for grounding the A140 tuner. 


Richard Piller


Cell 603 767 5330

On Nov 29, 2013, at 8:27, <terencesingh@...> wrote:


Some advise is needed with respect to the replacement of the factory installed 24VDC to 12VDC DC to DC Convertor.

We are about to install our Icom M802/AT140 SSB Radio.

The existing 12VDC wiring system is quite mess and includes a separate 12VDC battery that was used for the previous SSB installation.

I have heard that an Isolated ground DC to DC convertor should be used. These are used in systems that are ether positive ground or with floating ground systems.

I am pretty sure that our vessel (SM#196) does not have a positive ground system. 

Did Amel built their boats with a floating ground?

What does this mean with respect to installing a DC to DC convertor?

What are the ramifications for using a non isolated DC to DC convertor?


Any help understanding this is much appreciated.



SV Libby SM#196

San Diego



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