[TG] [TG11] Axiom 12 can't find Radome

[Vettepro]

I have an Axiom 12 and an RD418HD Radome. The radome is powered by a separate switch at the helm. It seems that the MFD can't find the radar at times. It has done this a couple of times and then seems to work again. It was working the other day but yesterday it would not work at all.
The only difference is that the drain line is now connected to one of the engine blocks whereas before it was not yet connected.
I have a brand new RAYA80228 Radar cable, so I'm assuming that's not it.
Is there a sequence to be followed when firing up the MFD and radar? Do I let the MFD fully boot up before powering the radar or does it matter?
I think it "sort of" sees the radar as it displays the message "4KW 18" Digital Radome (-20158) Connecting to Radar" before timing out and telling me that no Radar was found.
Should the radome need to be sent in for service, what is the procedure? Do I need to take it to a local dealer or can I send it in directly?
Thanks

[Tom - Raymarine - Moderator]

Hello Vettepro,

Quote:The only difference is that the drain line is now connected to one of the engine blocks whereas before it was not yet connected.

Have you tried disconnecting that drain line again?
You should not make extra connections between your DC system and a sea earth, that can cause a range of problems including a ground loop that may introduce noise rather than reduce it - you could also cause an electrolysis problem, depending on what other pre-existing connections there are on the boat. If you are going to connect your product drain wires/grounding points to a sea earth instead of simply to battery negative as would be more common, it needs to be a single, dedicated RF ground point for all of the electronics, not separated ones for each.

Quote:Is there a sequence to be followed when firing up the MFD and radar? Do I let the MFD fully boot up before powering the radar or does it matter?
I think it "sort of" sees the radar as it displays the message "4KW 18" Digital Radome (-20158) Connecting to Radar" before timing out and telling me that no Radar was found.

No, there's no special sequence except for Quantum radars running older software, where they could settle in a sleep mode if left powered for a long period with the MFD off (for anyone else reading this.) You can power your radar and display in any order.

The fact that the radar is listed as a source in the radar page but the connection times-out suggests to me one of two things:

1. Unreliable network connection. Possibly that new earth connection is exacerbating noise rather than abating it, or you have a poor network connection somewhere, but the 'announcement' of the radar service on the network requires much less bandwidth and less network reliability than the subsequent communications to initiate transmission and send the radar video.
2. A voltage drop. That symptom of the radar being available only intermittently and 'disappearing' as soon as you try to start the radar sounds very like a power supply issue. When the radar's in Sleep mode it draws very little current, but each step from there to Standby and then Transmit draws progressively more current and
   therefore will pull down the supply voltage more. If that drop is low enough, the radar's processor won't be able to run and it will stop being able to communicate with the display.
   

Of the two, from my experience and from the symptoms you describe I would say power is much more likely.

Quote:Should the radome need to be sent in for service, what is the procedure? Do I need to take it to a local dealer or can I send it in directly?

It doesn't sound at this stage as if the radar's faulty, but if it were then you could get it back either to the dealer you bought it from, or your nearest Service dealer (tick 'Certified Installation' at https://www.raymarine.com/buy/find-a-dealer.html) or our own service centres (select 'Book a repair' at https://www.raymarine.com/view/index-id=779.html.)

Regards,
Tom

[Vettepro]

I'm missing something.
This is a quote that Chuck wrote:
"Should the vessel be equipped with a bonding plate and bonding cable, then the drain leads from marine electronics should be connected to the vessel's bonding cable."

My boat has a cable that connects all of the through-hulls to each other and is also attached to the engine block. I attached my drain to the same point this cable is attached to the block. Should my bonding cable not be connected to the engine block?
I ran a 10 Ga. wire directly from the battery to the Radar cable (with a fuse in line just in case) just to test the power theory, as I also suspected a low power situation. That did not help.
I have not disconnected the drain line but will try that.

[Tom - Raymarine - Moderator]

Hello Vettepro,

I should be careful here not to contradict local guidelines or practice - I'm in Australia and our bonding practices are no doubt different in some details to yours - but the key thing from the point of view of an RF drain is a single point, with the drain wires of all of the products at a common potential. This usually involves bringing the drains of the electronics at a helm station to one junction and then running a single cable from there to whatever your RF ground is. You should not have multiple different paths back to that RF ground.
Here in Australia the common practice amongst electronics installers is to connect drains to the negative bus-bar, which then will generally go via the battery negative stud to the engine block. Because we have a high preponderance of aluminium vessels I am always very careful to advise owners not to make their own connections to new 'grounding' points. In theory the boatbuilder or original installer has planned the DC grounding or isolation and I would say that it's important to maintain the scheme they've used and not make new connections to earth.

By the way, since I'm in a different part of the world, I'll clarify the way I am using the terminology:

• Earth: sea-water potential.
• Ground: the reference potential used to drain away noise from electronic systems. Not current-carrying. Product drain wires and ground tags connect here.
• Supply negative: the current-carrying return - battery negative or equivalent. May be bonded to earth or be isolated/above-earth, depending on vessel and system design.
• Bonding: the practice of joining vessel metalwork to a common potential to reduce galvanic corrosion.
  

On the power supply - running your own cable is a good test, and this proves that you don't have a significant power supply drop between the battery and connection point, but does not absolutely rule out supply as the cause. I know it's a new radar cable and *should* be fine...

Regards,
Tom