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Mobile Installation RFI advice

This forum is dedicated to helping people with questions about installing radio equipment in vehicles. This can include antenna installs, electrical wiring questions/problems, and mounting systems. Pictures of installs are welcome.

Note: Discussions regarding lighting, sirens, and other equipment now has its own forum in the 'off-topic' section below.

Moderator: Queue Moderator

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x1sspic
Posts: 257
Joined: Thu Apr 11, 2002 4:00 pm
What radios do you own?: AstroSpectra XTS3K XTS5K APX7K

Mobile Installation RFI advice

Postby x1sspic » Sun Sep 06, 2015 3:27 am

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

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Wowbagger
Aeroflex
Posts: 1287
Joined: Tue Dec 10, 2002 10:46 am

Re: Mobile Installation RFI advice

Postby Wowbagger » Sun Sep 06, 2015 4:17 am

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.
This is my opinion, not Aeroflex's.

I WILL NOT give you proprietary information. I make too much money to jeopardize my job.

I AM NOT the Service department: You want official info, manuals, service info, parts, calibration, etc., contact Aeroflex directly, please.

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Bill_G
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Joined: Thu Sep 17, 2009 5:00 am

Re: Mobile Installation RFI advice

Postby Bill_G » Sun Sep 06, 2015 4:19 am

Shutting off the engine cures all your woes?

User avatar
x1sspic
Posts: 257
Joined: Thu Apr 11, 2002 4:00 pm
What radios do you own?: AstroSpectra XTS3K XTS5K APX7K

Re: Mobile Installation RFI advice

Postby x1sspic » Sun Sep 06, 2015 4:35 am

Correct, shutting off the engine cures all my woes. Even with everything else turned on.

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Bill_G
Posts: 3058
Joined: Thu Sep 17, 2009 5:00 am

Re: Mobile Installation RFI advice

Postby Bill_G » Sun Sep 06, 2015 4:56 am

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?


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