VHF Interference from Raychart 630 Plotter

[Tevake II]

I have a rather bizarre problem which I have been unable to resolve. Any assistance would be greatly appreciated.

Installation:

• Boat has an extensive Raymarine ST60 based system, including a Raychart 630 Plotter, all connected by Seatalk
• Communications are via ICOM M304 VHF and Barrett SB250 HF. The VHF is installed adjacent to the plotter with various cables in close proximity to each other.

Problem:

• The Raychart 630 generates VHF interference to a squelch breaking level on Channel 16 only and sufficient to render this channel unusable when the plotter is on. All other channels are clean.
• The interference extends to not only the installed ICOM, but also to any handheld VHF anywhere on the boat.

Attempts to resolve:

• Have fitted ferrites to everything in and out of the plotter.
• Have run the VHF from an independent power supply via an emergency antenna well separated from the plotter.
• Net result, nil improvement.

Before applying the blunt end of an axe to the Raychart 630 and trying something else, I would be very interested to hear from anyone who has expereienced similar problem and whether they have found a way to resolve.

[GordMay]

Greetings and welcome aboard the CF, Tevake II.

Although I cannot offer any specific help, I’m certain that your very well written question may generate some interesting and helpful discussion.

I don’t recall reading a better organized or more coherent and unambiguous technical question.

[BubbleHeadMd]

What does the chart plotter use as a ground? The interference is so widespread, that it's almost like the chartplotter is bleeding a signal through the boat's grounding system or sharing a ground with the VHF antenna, and the chart plotter's interference is actually being transmitted through the VHF antenna.

Since you say that this renders a handheld VHF useless, anywhere on the boat, that would seem to support this.

Try grounding the chart plotter differently. Get it off of the VHF radio's ground system and see what happens.

[btrayfors]

Clearly the RFI is being radiated, not just induced into the power or signal cables.

Try turning off the installed VHF and disconnecting both power and antenna cable. Now, turn the chartplotter on and see what you get with a VHF handheld. If you still get interference on Channel 16, the chartplotter itself is at fault and Raymarine ought to be ashamed. Doubt if you'll get much help from them (or their new owner, FLIR), but it's worth a try to tech support.

If you DON'T get RFI interference, then the problem is likely some weird interaction between the chartplotter and the adjacent VHF. Try temporarily moving the VHF to a distant location, using an extension coax and 12V power cable.

Bill

[hellosailor]

Is this Raychart still under warranty? I ask because I'm rashly guessing that Australia, like the US, requires electronics generally not cause RFI, and Raytheon (whatever their name is this year) might be familiar with the specific problem and cure for it. Often manufacturers can tell you exactly what part will curb RFI, and many will send it out to customers who call with a complaint.

Even if it is not under warranty, I'd still suggest contacting Raytheon directly to see if they have some specific information about it.

[Tevake II]

Thanks all for your inputs on this one.

The more I think about it, the more convinced I am that it must be the result of an internal fault in the plotter.

Why it affects VHF Ch 16 only remains one of the unsolved mysteries of the sea.

Re "support" from Raymarine (or whoever), the plotter is about 10 years old so well out of warranty. The local dealer shrugs his shoulders and suggests I buy a nice new C or E series plotter for $6k or so and then replace all my electronic charts because Raymarine has "progressed" from CMap to Navionics.

Raymarine Australia do seem to still exist, but mumble about the unit being retired, no longer supported etc etc. I'll keep prodding on that front.

[hellosailor]

Given that the unit is ten years old but apparently the interference is a new issue?

It might be worth oprning the unit up and examining the circuit board with a bright light and magnifier. As electronics age, they OFTEN develop hairline cracks at cold solder joints, and that can cause all sorts of problems. There were also a rash of bad electrolytic capacitors from various "cheapest possible" Chinese sources, which are visible as "gunk" leaking out of them and onto the circuit board. While the eyeball isn't as precise as electronic testing--these kind of visible faults can often locate problems that are cheaply cured. For instance, the RFI could be caused by one filter capacitor that has gone bad and is leaking, or one cold solder joint on a shielded portion of the board.

You don't have to know how to make spaghetti to understand what one broken piece of it looks like. Same thing for these simple flaws.

[Tevake II]

Thanks for the further input. I think your right - time to open it up and have a poke around.

The problem is not exactly new. Has been present to some extent since I bought the boat five years ago and we've been living with it, but I feel it's getting progressively worse. I initially thought it was a problem with the VHF transceiver and replaced that to no avail. It was only after doing that that I noticed it was affecting the handheld as well!

Good suggestion re dud capacitors. I've had a couple of PC motherboards go belly-up as a result of that particular affliction. A slowly deteriorating dry joint or hairline crack would be another definite possibility.

Will let you know if I find something.