Radio interference

Woodstock · May 8, 2006

I broke down and got a mixit2 to mix my radio/ipod/gps/radar into a single audio source for my starcom unit.

I tapped the power directly from the fuse-box to starcom unit, so it's powered by the bike. I didn't have the right audio cables last night, so I just left it turned on, so it would be on when on bike power, and I'd pick up a few extra cables on my way home. When I turned on the radio (currently, just an simple portable AM radio), I got a really loud static hiss which kept time with the headlight modulator. I put the light on lowbeam (turning off the modulation) and it stopped, but the reception of the AM radio was still much worse. I figured it had something to do with the MixIt2, so I pulled over and put the hazards on. When they flashed, same thing, audio interference keeping time with the flashing. After pulling the seat up, and turning off the mixit2 at the on/off switch, the interference stopped and it was back like it was.

NOTE: There was _no_ audio running through the mixit2, it was just powered up, no other plugs other than power.

Could the mixit2 really be that RF noisy to amplify the changing load on the electric system?

I know I should get a better radio with an antenae and all, but this was unexpected.

Any ideas? Do I just have to live with it until I get a better radio? Any good small AM/FM with an antenea or whatever is needed to prevent this interference?

twowheelnut · May 8, 2006

Ground problem?

Woodstock · May 8, 2006

twowheelnut said:
Ground problem?

Certainly possible, I guess. But the mixit2 doesn't have any audio signal running through it, and the radio is battery (AAA) powered, so no bike ground there. The starcom (and mixit2) doesn't have the best ground (it's not running back to the bike's battery), but I still find this a bit odd, given that the only addition is having the mixit2 with power from the bike.

twowheelnut · May 8, 2006

...and it works without the MixIt just fine?

Edit: Why do you still need the Starcom with the Mixit?

Woodstock · May 8, 2006

twowheelnut said:
...and it works without the MixIt just fine?

Right, it works if I just switch the mixit2 off. The audio from the AM radio goes directly to the starcom.

twowheelnut said:
Edit: Why do you still need the Starcom with the Mixit?

The starcom provides the intercom system and future bluetooth or bike2bike radio. The mixit2 audio output will go into the starcom1 audio input.

twowheelnut · May 8, 2006

Ground loop between the two, then.

Woodstock · May 8, 2006

twowheelnut said:
Ground loop between the two, then.

Between the mixit and starcom? They both get their power from the same hot lead running from a fuse box back to the rear of the bike, and both their grounds are connected to the same place as well.

twowheelnut · May 8, 2006

Sorry, I meant the audio connections... The Starcom requires GL's from the GPS and detector, maybe it's looking at the MixIt in the same way?

Woodstock · May 9, 2006

twowheelnut said:
Sorry, I meant the audio connections... The Starcom requires GL's from the GPS and detector, maybe it's looking at the MixIt in the same way?

But there's nothing feeding the starcom using a bike ground, radio is AAA based.

Oh, yea, one other point I should have mentioned. I don't get any interference when just playing the ipod.

It really just seems like RF interference to the AM radio generated by the mixit2 getting power. I have one other thing to try when I next get to the battery.

Groo · May 9, 2006

Try disconnecting the Mixit from the bike power, and pop in a 9V battery instead and see if anything changes.

Woodstock · May 9, 2006

Groo said:
Try disconnecting the Mixit from the bike power, and pop in a 9V battery instead and see if anything changes.

Good idea. I should have thought of that. brb...

ok, I did the test, and it confirmed that the interference is from the bike's electrical system (which I guess I knew, since it was "in time" with the modulator and the 4way flashers).

Groo · May 9, 2006

So with the battery running the Mixit the problem goes away? Seems like there's some feedback loop then ... if you can, you might make your connections on different hot leads, and to different grounded locations and see if that helps any. I also seem to recall that John sold a power filter to supplement the original Mixit... maybe the filters built into yours went kerplooey...

In any case... I'd give John a buzz, and see if he can help... after all, he designed it.

Bounce · May 9, 2006

The bike's charging system dumps excess capacity to chassic ground (nature of the regulator). You'll need to run all audio grounds back to battery ground to isolate it from chassis ground and the interferance it will create.

I've found that the longer you ride the more the interferance increases until it's at it's max with a fully-charged battery. That would seem to indicate that more capacity is being shunted to the chassis and then hitting the devices using the frame for a ground.

PerfectBlueride · May 9, 2006

Besides that AM radio? :blink: Doesn't work that well anyway.

You might also need a filter of some :blink: sort

Good luck let us know how it works out for you

Woodstock · May 14, 2006

I had some time today, so I ripped into the starcom/mixit wiring and disconnected the ground (from those two devices) from the chasis, and ran a ground all the way to the battery from those two devices. Again, the AM radio is just AAA battery powered, so no bike power there.

The interference is still there, in time with the headlamp modulation or 4way flashers, if used (obviously, the latter isn't a real issue, but the former is). It looks like the mixit is generating an RF field in time with load changes on it's power (again, if the mixit2 is 9V powered, no issue). The hot lead to the starcom and mixit, comes from a relay-switched fuse block.

twowheelnut · May 14, 2006

Welp, time to take the switched hot leads back to the battery, too. See what that does. Dang, dood, it shouldn't be this hard, should it? :blink:

Woodstock · May 14, 2006

Yea, I'll try that, but I do need them to be switched, so it's more just a diagnostic experiment. Neither the flashers, nor the modulator is connected to the fusebox or relay from which the starcom/mixit2 gets it's power.

I may look for a better AM/FM radio, but I'd like to verify that's going to fix my problem.

Groo · May 14, 2006

Did you try John Brown to see if he has any insight?

Woodstock · May 14, 2006

Groo said:
Did you try John Brown to see if he has any insight?

Not, yet, but I'll get an email off to him tonight. (Thanks for the reminder)

Radio interference

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