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GeoffSchultz GeoffSchultz is offline
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First recorded activity by BoatBanter: Feb 2007
Posts: 52
Default Supressing RF Interferance from NMEA Junction

On Jul 4, 6:25 pm, Larry wrote:
GeoffSchultz wrote groups.com:

How can I shield the bus bar so that I can distribute the data and
bridge the AIS data such that I don't generate RF which interferes
with the VHF?


-- Geoff


VHF is much easier to fix than HF......

Where is the VHF ANTENNA, in relation to the AIS data lines? Where is
the VHF radio? If they are near it, move them, instead of trying to fix
the unfixable, namely, trying to shield stupid NMEA open-wire technology-
in-the-plastic-boxes. Move the radio/antenna away from the noisy
nonsense...which is MUCH easier.

The VHF antenna system is a closed system, nicely shielded from the
antenna to the radio. One bad thing happens...loose connectors or
corroded shields open up this coaxial system to the outside noise
intrusion. Check all connections to make sure the SO-239 connectors are
tight. If any of the shields can be moved in the connectors, rebuild the
connectors so the shields are making an ALL AROUND good connection.
Crimped-on coax connectors are fine. So called "solderless" connectors
from RatShack are NOT. They come apart too easily.

Larry


The VHF antenna is forward, on top of the mast; the VHF radio is at
the nav station; the patch panel is mounted behind the VHF radio; the
AIS cable run from the patch panel to the C80 which is at the wheel;
the two cables are only in the same proximity for a few inches.

Moving the VHF really isn't an option. I think that I'll follow up on
Meindert's suggestions.

-- Geoff