SSB TX causes Bow Thruster to surge

[jefndeb]

Hello,

Been trying to eliminate some EMI issues with my boat when keying the SSB on certain bands. Seems to happen more on 75 Meters.

I have installed numerous Suppression Ferrites in various locations in an effort to stop this problem.

I have installed them at the radio DC power cable, tuner data cable and M802 remote head data cable.

I have a 23 ft Shakespeare vertical Whip antenna with an Icom M802 SSB with an AT-140 Tuner.

Anybody have a suggestion of a other locations?

Jeff

[billknny]

You are working the wrong end. When you key your SSB there is SUPPOSED TO BE EMI. That is exactly the point of the radio, to transmit electromagnetic radiation!

The problem you have is that radiation that you generate when you transmit is being picked up by your wiring and generating voltages where they shouldn't be. It is not at all unusual for lights to flicker, but for bow thrusters to run is a bit... exciting?

Fixing this can be complex, but a good start is to twist the wires that are picking up the power. That negates the effect. Next, is to put the wires in a (grounded) metal conduit.

[jamhass]

What (normally) controls your bow thruster? I suspect you have a wireless controller, possibly a low-voltage relay/contactor. In either case, I would suspect that turning off the main bow thruster breaker would be your easiest fix. Otherwise, perhaps adding chokes to the various thruster control modules might work.

[GerryL]

Correct, you want to put the ferrites on the leads to the equipment that is being affected (close to the equipment). I've had cars that had all the instruments go crazy when transmitting, and one truck would accelerate if I transmitted with the cruise control on. LOL

[jefndeb]

ok, that thought had crossed my mind, there are two joysticks on the lower helm (bow & stern) that might be a place to look at...

[Brian.D]

What is being proposed is just applying a band aid. You need to find the source. I can guarantee you that what you see should not be happening. The source problem is your SSB system, not the bow thruster.

Start by not adding things but looking at things like your ground. A bad ground is going to cause stray RF, or EMI. Check the ground from the tuner to where ever it is connected. Disconnect it, clean it, lube it, then reconnect and make sure the connection is solid.

If you are concerned about common mode currents which can also be causing your bow thruster issue, add a 1:1 current balun at the input of the tuner. This will prevent common mode currents flowing back to the radio.

The antenna connection/tuner connection need to be taken off, cleaned, lubed and then reconnected. This could also be a cause of your issue.

My money will be on the ground from the tuner to whatever you are using as a counterpoise be it your engine block, KISS, or even the sea through one of your through hulls.

Check all those before adding more ferrites.

JMHO

[a64pilot]

I guess I’ll argue but an SSB is dumping a lot of RF into the air, and not everything is compatible.
I have done a lot of EMI / EMC test flights, the EMC stand for electromagnetic compatibility.
You have a source (the SSB) and a victim (the thruster), you May can shield the victim, but I think your not going to be able to suppress the source.
It’s normal to see interference with high RF outputs.
Used to be you would see big Linear amps on OTR trucks, but since the advent of computer controlled engines, not so much.
I know of one driver that ruined a whole reefer truck full of frozen meat, every time he keyed up, it put the reefer into defrost mode, and of course the whole load defrosted.

[Seighlor]

Haven't used SSB for awhile. But when I did, it would drive the autopilot nuts. Others I was competing with had the same experience.

[abarrow]

When I first read your post the first thing that came to mind was "why are you using your bow thruster at the same time as transmitting?" So, I guess you mean it just turns your bow thruster on. As others have said, there are some things that you may not be able to resolved, considering your SSB is dumping a lot of RF into your boat, and your boat ground. So there are a few things to consider:
- Look at your grounding system as a whole. Is the ground you are using for your SSB antenna the same as your ship's electrical ground? Is your antenna ground well connected to the sea?
- How exactly is your thruster activated? A contactor? If so, you are probably generating enough voltage on the control wires to it so that when you are transmitting to activate the contactor. What about putting a capacitor between the terminals on the contactor to bleed the RF to ground? Also, if there is an electronic control box running your thruster, consider the same treatment for the power leads to that unit.
- Generally, because you are using a base tuned whip right no the deck, your boat is going to be flooded with EMI when you transmit. Every single wire is a receiver for that. Ferrite cores help, as do capacitors. You might also consider putting in common mode filters around.

[jefndeb]

Thanks for all the input....Yes I need to do some investigating....

[hzcruiser]

Originally Posted by Brian.D

What is being proposed is just applying a band aid. You need to find the source. I can guarantee you that what you see should not be happening. The source problem is your SSB system, not the bow thruster.

I'd say there is a bit of both: Using your HF radio is putting a fair bit of energy into the air, hence you want to:

- get all or most of the energy towards the intended direction, IOW: avoid high radiation inside the boat
- protect other equipment of the residual radiation you cannot avoid, which means using ferrites etc.

So yes, as mentioned, make sure your antenna system is efficient and remember: the radiating part starts at the tuner. What counterpoise do you have?

Then, apart from ading ferrites to the components that are still playing up, consider reducing your HF energy in the first place.
My guess is too many people keep blasting the maximum wattage of 100W or even more out the finalseven if they might only need 25W to reach their counterpart.

As a side note, there is a whole "world" of "hams" trying to use as little power as possible to reach faraway places. The mode is called "QRP" as in "reduced power mode". With less than 5W at the antenna they can cover thousands of miles.

[CF32907]

Hi All, CaptVR here.
Don't know where your antenna is mounted or how close it is to your remote for thruster, if you can, try raising your antenna 5' or more.
I installed a high watt output on my 60' schooner. Insulated back stay for antenna. Antenna cable was attached 3' above deck to keep the feed as short as possible. When keying mike, cockpit lights would flicker, florescent would turn on, old Nelco loran would go nuts. A friend in the radio shop told me to turn my backstay upside down. Know my feed was about 18' above deck and the problem went away.
Capt. Vince Rakstis, Ret. St.Petersburg, Fl.

[stormalong]

You might also want to look at your coax cable routing. Does it run in the same bundle as the control cables for the thruster? If so separating them as far as possible may solve the problem.

Another suggestion. Replace the control cable with shielded cable and ground the shield.

[hzcruiser]

Originally Posted by CF32907

[...] A friend in the radio shop told me to turn my backstay upside down. Know my feed was about 18' above deck and the problem went away.
Capt. Vince Rakstis, Ret. St.Petersburg, Fl.

That's definitely a good option, as the current is at a maximum at the feedpoint. Only thing is that it's not always feasible or at the very least, more difficult to install.



Is yours a single band antenna or do you have a tuner up in the rig if you want to use it on multiple bands?