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Mobile Installation RFI advice

Posted: Sun Sep 06, 2015 3:27 am
by x1sspic
I recently upgraded to a pickup truck that has very little roof clearance in order to fit into my garage. I had wanted to drill and locate my antenna in the center of the roof. I compromised and used an L-bracket on the hood. Unfortunately, since it is next to the engine compartment there is some RFI from the engine. It does reduce sensitivity for weak analog signals (fringe) a little, but the effect that I have found to be more problematic is the hit digital (P25) takes. In analog it isn't that noticeable, but the P25 receive sensitivity takes a big hit. This is a VHF installation using a Laird 5/8 wavelength antenna with elastomer spring on a brass NMO mount. Any advice for trying to address this? Thanks,

Scott

Re: Mobile Installation RFI advice

Posted: Sun Sep 06, 2015 4:17 am
by Wowbagger
1: Make sure your hood is well bonded to the frame - I'd install a separate ground strap from the hood to the frame just to be sure. You want the hood acting as a ground plane and a shield, not an antenna.
2: Get some snap on ferrite cores, and put them on your injector wires and ignition wires.
3: See if the noise is your fuel pump - if so, install an RF filter on it.

Re: Mobile Installation RFI advice

Posted: Sun Sep 06, 2015 4:19 am
by Bill_G
Shutting off the engine cures all your woes?

Re: Mobile Installation RFI advice

Posted: Sun Sep 06, 2015 4:35 am
by x1sspic
Correct, shutting off the engine cures all my woes. Even with everything else turned on.

Re: Mobile Installation RFI advice

Posted: Sun Sep 06, 2015 4:56 am
by Bill_G
Have you done anything like the things wowbagger described? ie: bonded the hood, buffed the ground on the tmb, re-routed the coax, rework the radio return line connection, add a filter to the A+, experiment with a mag mount on various locations of the vehicle?