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-   -   vhf / gps interference (http://www.sailnet.com/forums/gear-maintenance/34644-vhf-gps-interference.html)

chuckg5 07-09-2007 09:53 PM

vhf / gps interference
 
just installed a Garmin 3206 in the nav station
already have a Icom 502
the minute I turn on the Garmin, channel 28 on the vhf comes on with static an stops the scan
i know they're right next to each other but the garmin shoulddn't be putting out radio waves.
does any one know what's up with this?
all power wires meet up in the same ground an positive bus bars
i cancelled out channel 28 on the scan but that doesn't help
thanks!

sailingdog 07-09-2007 10:02 PM

How do you have the antenna coax cable run for the VHF?

BTW, the FCC statement on the equipment probably says that it is allowed to give off some radio wave interference.

chuckg5 07-09-2007 10:20 PM

Saildoggy
straight shot coax into vhf, nothing fancy
r u suggesting maybe more grounding of said coax, close to the box?
this is in recieving mode, I'm not even transmitting

knotaloud 07-09-2007 10:31 PM

I remember reading somewhere that if your GPS antenna cable runs too close to the VHS coax, that could do it, or if your GPS antenna cable has a big loop or coil, it can act like a radio antenna and amplify radio interference. And I would ground the coax

SEMIJim 07-09-2007 10:34 PM

Just tighten-down the squelch on the VHF rig a bit. All electronics generate RF noise. All. You can pick up some ferrite donuts at certain electonics supply places or Ham Radio swap-and-shops, loop your radio and GPS power through those a few times and reduce somewhat any RF noise that's leaving/entering through the power leads. (That'll also somewhat reduce engine alternator noise in the radio.) That may help some. Other than that: Just make sure your grounding is good, and your coax in good shape and well-terminated at both ends. That's about all you can do.

Jim

SEMIJim 07-09-2007 10:42 PM

Quote:

Originally Posted by knotaloud
I remember reading somewhere that if your GPS antenna cable runs too close to the VHS coax, that could do it, or if your GPS antenna cable has a big loop or coil, it can act like a radio antenna and amplify radio interference.

Well... close. The GPS might emit some amount of "random" RF noise, across the spectrum, from its receiving antenna system. All radios, even pre-digital ones, do. (Tho the pre-digial ones weren't random. You could tell what station they were tuned to by what they were radiating.) Shouldn't be much, though. All a loop in the GPS' antenna line will do is perhaps radiate more noise in in the area of the loop.

Quote:

Originally Posted by knotaloud
And I would ground the coax

It'll already be grounded via the chassis of the radio--and possibly at the antenna end, as well. (Depends on the antenna type and mounting method.)

Jim

sailingdog 07-09-2007 11:21 PM

I would run the VHF coax antenna cable as far from the GPS cabling as possible and add ferrite cores to the cable. Both should help reduce any interference caused by the GPS.

chuckg5 07-09-2007 11:21 PM

I do have numerous loops in the gps cable
i'll try a move the coax an gps cables furthur apart , tommorow
thinking of wrapping aluminum foil around the power inputs of both as
a test to see if that can eliminate the noise
thank you for replies!

SEMIJim 07-09-2007 11:28 PM

Quote:

Originally Posted by chuckg5
I do have numerous loops in the gps cable

It's best to avoid loops in antenna cable, even if it's just a receiver cable, if you can. You certainly don't want a bunch of looped GPS antenna cable right near the VHF radio.

Quote:

Originally Posted by chuckg5
i'll try a move the coax an gps cables furthur apart , tommorow

That would be best. The shield on antenna cable is imperfect.

Quote:

Originally Posted by chuckg5
thinking of wrapping aluminum foil around the power inputs of both as
a test to see if that can eliminate the noise

My guess is all that'll accomplish is looking messy and create a fire hazard.

Quote:

Originally Posted by chuckg5
thank you for replies!

You're welcome :)

Jim

chuckg5 07-09-2007 11:53 PM

I know , Jim
the aluminum would just be a test shield for r/f
absolutly no good near buzz bars:)


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