Can my SSB Blow up my autopilot? - SailNet Community
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post #1 of 3 Old 01-29-2011 Thread Starter
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Can my SSB Blow up my autopilot?

I just installed a new SSB, a 100 amp max unit, on my sloop and the reception was great. Today I broadcast for the 1st time and someone 500 miles away said they heard me loud and clear. So I decided to go for a sail to celebrate. Motoring out to the bay I engaged my Alpha 3000 autopilot, and she was not happy (and neither was I). She is off 120* from the ships compass, and when I move the dial to go to port she steers the boat to starboard and visa versa. And if I call for a significant course change she does a 360! The SSB was off during all of this, and the autopilot was off during my SSB transmission.

Could there be a connection between my autopilot problem and my SSB? I have heard that while the autopilot is steering, an SSB transmission can cause it to misbehave, but when one was on the other was off. Could my SSB transmission and the resulting RF toasted my autopilot compass? I have check all autopilot connections and made sure that all things on the boat are stored when they always have been. The only thing near the fluxgate compass is one of the radials in the bilge, but I'm told that with 2 dynaplates, this should not have wacked my compass. This autopilot is the greatest and has been the single best thing I have ever purchased for my boat. It is conceivable that the autopilot failure is not related to the SSB, but the Alpha has been so reliable that I doubt it. Any ideas?
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post #2 of 3 Old 01-29-2011
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With stray RF, just about anything is possible. Unfortunately. It's conceivable that the RF got into the autopilot electronics, not just the fluxgate compass. Kinda sounds like that to me, since the controls seem to be working in reverse.

One large builder of high-end trawlers had continuing problems with SSB radios affecting their autopilots. Reportedly, they cured them by installing a different RF ground (the KISS-SSB radial ground system).

On my own boat, I once had a setup wherein I merely had to push the mic button, not even transmit, in order for the SSB to turn on the fan on my Espar diesel heating system!

How to avoid all that? Run cables as far from others as possible. Use ferrites liberally on all signal, power, and control cables. Wire the SSB directly to the house batteries, not thru a panel, with appropriate CPDs located near the batteries. Use an isolator, like those made by Radio Works. Be sure the RF ground is not connected to the boat's DC ground, AC ground, lightning ground, or bonding ground systems. Ensure that all connections are clean and tight. Pray.

It's possible, of course, that the Alpha is acting up on its own, unrelated to your SSB transmission. Check the rudder feedback mechanism and cable.

Good luck,

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post #3 of 3 Old 01-29-2011
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I have a friend that has this going on, so you are not alone. I bought him a handful of ferrites to install and we are going to take a look at his ground system. But also, you might want to check all your antenna lines and connectors. On my last boat, I had a section of GTO-15 wick up some moisture and the result was I got a lot of RF on some bands but not all. Caused a lot of really strange results from all sorts of lights going off to interferrence with my chartplotter.
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