Navnet 3D causes VHF radio interference



This is a new install of a 3D. It has the 1000watt FF, gps and radar.

When I turn the unit on the meter on my VHF indicates reception of a radio signal and all incoming calls are blocked.

I isolated the vhf radio from the entire boat electrical system by connecting it to another battery. Still does the same thing. For some reason the Furuno broadcasts an RF signal that blocks all incoming vhf transmissions.

Any suggestions?
It sounds like you might have some sort of a power or grounding issue on the boat. I would look at the bonding system that is connected to the fly nut/wing nut at the back of the display. Ensure that you haven't connected the power cable shielding to anything. (This shield is internally grounded in the unit and connecting the other end will create a path of electrical flow, contributing to possible grounding loop or power differential issue.) The bond at the fly nut should be direct to the bonding system (not other units) and the bounding system should go to a hull plate in contact with the water. You should be very aware of what the transducer cable and data cables are run alongside. You might have some sort of inductance problem. If you doubt the unit, you can send it to the service center for testing. In all the case I have seen, it has be caused by a problem on the boat or the routing of cables. You might also consider adding a power choke/filter to the power lines on the radio. This normally helps radios from getting noise in on the power line. I would also you verify the radio is mounted outside the compass safe distance specified by the MFD. (About 1.5 feet)
OK here goes:

This is an installation in a new 28' Aluminum Hulled boat. It has the 3D with one ICOM Marine VHF and one Icom 2 Meter radio. We have an older identical boat with identical radios except the other boat has the VX2. We had the electronics installed at the boat manufacturer.

1. There was no bonding wire hooked to the wingnut. However hooking one up had no effect.

2. The Marine VHF is able to receive transmissions with some degradation, while the 2 meter which probably has a more sensitive receiver is totally blocked. Both radios transmit with a good 5/5 over at least 5-10 miles on the water.

3. Changing the coax connection from the antennas from one radio to the other has no effect. The 2 meter still blocked on the Marine VHF antenna.

4. On the off chance the radio was defective I pulled the 2M from the older boat and hooked it up in the new boat. No change both 2M radios showed the same symptom.

5. Pulled the CB on the DFF fishfinder with no change. Still blocked.

6. The wires for both the MFD and the radios disappear into the ceiling, and while possible would be a major PITA to drop the ceiling to check their layout.

Maybe there might be more troubleshooting you can think of. Tomorrow I thought I would see if the older boat setting next to the new one received the RF signal that is blocking. I also thought of using a handheld Battery jumper as the power source for the 2 Meter?
Spent about two hours today on the boat trying to figure out what going on. It is definitely related to the GPS antenna/sensor and the 2M radio/ coax connection.

There is no RF transmission I could pick up with a handheld, so started with the antenna of the 2M. With the antenna disconnected and the handheld broadcasting it received the signal loud and clear. No blocking.

I went up and touched the GPS antenna and lowered it's mast, and the blocking signal went away momentarily. Seems like when the the GPS antenna is not grounded through the metal mast it is attached to the problem goes away.

I couldn't figure out how to depower the GPS antenna to see if that caused the blocking signal to go away.
It still sounds like a power/grounding issue or cables running too close together and getting some sort of bleed-over. I would look over the entire installation. I bet someone forgot a step or didn't follow the installation standards. Just because noise shows up at the GPS doesn't mean it is the source of the noise. GPS unit "receive" data and don't "transmit". If the GPS antenna had a problem it should not be enough power to JAM a radio. The GPS most likely wouldn't function either. You got a good mystery on your hands. I would recommend you speak with the boat builder and get system drawings (if you don’t have them) so you can narrow down the possibilities. It might require a good Furuno dealer at the boat to resolve. Let us know…