430W and 496 GPS antenna interference

I just finished installing a 430W in my RV8's panel. I also have a 496. Both antennas are mounted under the cowl. The 496 antenna is mounted on a shelf on the firewall and the 430's antenna is mounted on a shelf attached to the engine mount. I ran the cables together in a bundle that passes thru the baggage compartment tucked into the u-channnel that the baggage door hinge attaches to. The problem I'm seeing is that as soon as the 430W is powered up, the 496 loses all satelite reception. If I separate the antenna cables the 496 begins to see satelites again. It's hard to believe there is crosstalk but it appears there is. Has anyone else seen this?

Thanks,

Chris

Hello Chris,

I am not aware of any issue with co-located/routed GPS antenna coax, but there are antenna spacing requirements (minimum 6 inches).

Not sure if this has anything to do with this problem, but do you have at least 6.5 ft of antenna cable between the 430W and the antenna? For RG-142B or RG-400 cable, this will ensure that the minimum required 1.5 dB of cable loss is provided by the cabling. This is required for a GA35 antenna.

For a group of antennas listed in the installation manual, the required loss is twice this amount. Additionally, as specified in the installation manual, to maintain integrity of the WAAS signal, the GPS antenna coaxial cable must have a minimum of two shields (e.g. RG-400 or RG-142B).

If you are using a GA35 antenna, would you please email me the serial number?

We would be happy to answer any questions you have about your installation if you provide the details.

Thanks,
Steve

Thanks for the reply Steve.

My antenna spacing might be a bit close, but I removed the 496 antenna from the shelf and moved it a couple of inches further away and the problem still occurred.

I have approximately 15 feet of RG-400 cable (most of it coiled up) going to the 430's antenna. My installation manual states that the 430 must have a minimum of 3dB and a maximum of 7dB attenuation from the cable.

I'll email you the serial number of the GA35 antenna. Is there anything else you need to know?

Thanks