Potential interferences between SSB and Raymarine autopilot EV100 - what's your experience?

[MCD]

Hi Ericson community,

I'm about to install a new Raymarine EV100 wheel pilot on our Ericson 38 (the previous one's belt sadly broke on our first sail with the boat). I'm in the process of choosing the location of the different components and have options, for the sensor and the ACU100 in particular. Basically, one option consist in having a simple and limited SeaTalkng network and both components will be between 3 and 5 feet from the electric panel, the VHF and the SSB!
And that's this latter I'm worried about. I have read some posts online reporting significant interferences between the SSB and autopilot computers (it couldn't function with the SSB on). However, it was never for that particular autopilot but for older models.
The manual paragraph about the ACU location doesn't specify anything about proximity to cables and radios (the sensor part does). But there is a paragraph later that recommends to put every component at least 3 feet away from VHF and 7 feet away from SSB (which wouldn't be the case of my ACU for sure and borderline for the sensor). Anyone knows if that's to protect the VHF/SSB or if that's to protect the autopilot components?

So, here is my question: does anyone have experience with using the new Raymarine autopilots with the SSB on? If so, do you have interferences? How far away are you components from one another?

I also have another idea for spacing out the components more but it would of course require more SeaTalkng backbone cables and a larger network in general. I only want to do that if necessary. And even then, I'm wondering whether the proximity to the cable carrying the antenna signal from the SSB might be a problem... It's going to be hard to avoid them at all!

Thanks for sharing your experience with this
Marie
SV Tire Bouchon

Attached are the manual relevant paragraphs:

 

[texlan]

Hi MCD. I don't have particular experience with an autopilot being interfered with by an HF(ssb) radio, but I do own both an EV-100 (tiller model) and have owned/operated a lot of HF and VHF/UHF radios, (as well as some pretty powerful compact MPPT solar installs, including in a small boat next to the EV100) so I would like to say I have a lot of experience in RF interference rich environments.

I would not worry so much about the ACU100's physical location as I would worry about making sure not to run conductors (seatalkng/nmea2k OR power) to any part of the autopilot system close to and parallel with conductors attached to your SSB system (to include the tuner.) Of course you do want to isolate the EV-1 as far away from any moving magnets, ferrous metal or current carrying conductors as you can. On my boat my EV-1 is about 6 feet away from conductors that carry upwards of 70 amps and there is no observed impact to course holding in that situation.

Attempted Short explanation: Problems with radios happen when the transmission line + antenna systems represent unbalanced loads to the radio transmitter. With a perfectly balanced load, all of the RF energy in a, let's say, coax-based system travels on outside of the coax center conductor and on the inside of the coax shield. When unbalanced, RF energy follows additional paths: the outside of the coax shield, the case of the radio, the microphone cable, the attached radio-operator, down the DC power supply cables, and down the ground-cable (if there is one.) Oh and it is also radiated from theses paths, because it is unbalanced current. This radiation is what interferes with other sensitive electronics (like autopilots), specifically when it couples to other conductors attached to those electronics (Effectively the conductors become receiving antennas.)
This doesn't happen as often with VHF systems because unless you have corroded coax connectors (Hmm, masthead antenna?) the antenna systems for VHF systems are pretty darn close to 50 ohm balanced loads. SSB on the other hand, with the random-length antenna, antenna-tuner trying real hard to balance the load, and an almost always inadequate and asymmetrical counterpoise, almost guarantees this situation to some extent. The bright side is interference will only occur while transmitting.

All that said, my 480 watt MPPT solar array has conductors that travel within 2 feet of my ACU100 at one point, and very close to power conductors for that ACU100 for some distance, does not cause interference to my autopilot. (Though that array created a positively huge amount of interference to my VHF receive, until I put about 100 of the appropriate ferrite beads on the array-power leads to the panels to force the MPPT switching current to be in balance) It may be that my efforts to reduce the RFI from the array to my VHF actually created a situation where it never had a chance to interfere with the EV100 system so YMMV there, best to follow the rule to keep conductors that could carry RFI away from and not parallel to your AP wiring to eliminate RF-coupling of that RFI into your AP system.

Hope I wasn't too wordy !

Sean
WK7R
(extra-class amateur radio operator and certified dumb redneck, $.02)

 

[toddster]

I only have an old ST2000+, but I've noticed a more mundane problem: It and a lot of other stuff resets on engine start. Which I'm attributing to momentary voltage drop. I suppose that in some cases the SSB could cause something similar, but it's a much smaller load. Come to think of it, I don't think I've ever transmitted while under way. Anyhow, I don't think it happens since I replaced the battery bank. And I probably could/should isolate the engine load onto the backup battery.

Oh, and I did manage to create interference with the fluxgate compass by installing new stereo speakers. D'Oh! Gotta move one or the other of them.

 

[MCD]

Hi,

Thanks for your useful answers.
I discovered that, luckily, the SSB cables are run in a different location than most of the cables going from the panel aft. SSB goes in the liner of the aft cabin while the rest goes under the cockpit floor. This way I can have the SeaTalkng backbone away from the SSB cables, which may save the day! And I should be able to have everything at least 2 feet away from the SSB and panel (not sure about the ACU though since it does not seem to be a problem for it). I'm planning to have the sensor under the aft settee sit and the ACU either in the cockpit locker or in the locker under the chart table sit (that would make it much closer to the panel for better -less 12V cable to run- and for worst -potential interferences).

I'll post the outcome when the autopilot is installed (hopefully soon) and the SSB connected to its antenna (not on top of the list yet so it might take more time).

--
Marie
Sailing Vessel Tire-Bouchon

 

[bgary]

I did manage to create interference with the fluxgate compass by installing new stereo speakers.

(laughing) I rearranged some stuff on the boat a couple of years back, and some time later noticed some weird autopilot behaviors. Took forever to convince myself I wasn't...uh... hallucinating, or something.

Turns out, the fluxgate head didn't like having a spare alternator stored in a dinette locker just on the other side of the bulkhead.

 

[toddster]

I've been eyeballing the big empty space behind the galley range, and thinking that might be a nice quiet place to re-install the SSB unit and shorten up some cabling. Except I'd have to add a big loop to the feed line if I wanted to keep the SWR meter mounted in the panel. Ah well. Thinking about it is free.