RX and TX static

[Firefightingdude21]

I have a Motorola radius M1225 Installed in my 2015 dodge 2500. Before purchaseing my new truck I was having issues a lot of the time on our repeaters TXing and RXing. When moving the radio from one truck to the other I replaced the antenna wire and antenna mount. I had to mount the antenna onto the driver side fender due to height issues in garage. I have the same radio in another truck with a mag mount and have zero issues. Any ideas?

Thanks.

 

[jonwienke]

The first obvious thing is to check SWR. The mount does not look like it is well-grounded. The paint under the mount needs to be removed down to bare metal so the mount gets a good DC and RF ground, and all electrical connections need to be sealed with something to prevent water intrusion and corrosion.

 

[cmdrwill]

The first obvious thing is to check SWR. The mount does not look like it is well-grounded. The paint under the mount needs to be removed down to bare metal so the mount gets a good DC and RF ground, and all electrical connections need to be sealed with something to prevent water intrusion and corrosion.

Very good points to check.

What antenna is the OP using on the M1225?

Adapters on the antenna jack on the radio may have caused bad center pin connectivity.

 

[AZ_chris]

If that mount is sitting directly on the paint, you're not getting any ground to the antenna either.
You need to sand some paint off and get bare metal where the bolt meets the metal.

 

[mmckenna]

Some other things to check...

Make sure antenna coaxial cable is routed away from other vehicle wiring. There are a lot of noise generators in modern vehicles.

Make sure coaxial cable isn't getting pinched by the hood, or anywhere else. SWR check would probably indicate this, but not necessarily.

Also, depending on what type of NMO mount you are using, they may not seal properly. Since most NMO mounts are designed to go through the roof of the vehicle, they are not properly sealed on the underside. Using the external bracket mounts like that leave the underside of the mount, and the bare coax, exposed to rain, snow, road salts, etc. This can quickly lead to corrosion and create all kinds of issues, including static on TX and RX.
It's imperative that you properly seal the underside of the mount to keep it protected, and absolutely keep the water out of the inside of the coax cable.

 

[Firefightingdude21]

Thanks all for the replies!
I did not remove any of the paint under the mount before mounting, but under the screw to the fender has some paint removed. I will try removing some more of the paint. I don't have an SWR meter to check that. What would you guys recommend placing on the connection of the antenna, and the antenna wire? There really isn't any type of protection there.

 

[Project25_MASTR]

How is the power ran?

DC grounding of the mount shouldn't be a primary issue (once you snug them down they generally make contact), RF ground is more important (which can be 100% independent of the reference ground). I have used one of those mounts on a 2015 6.7 before and it is quiet as could be (no sanding necessary) and oddly enough, it's running a M1225 as well. Chrysler is notorious for having alternator noise on their engines (the Cummins diesels were generally an exception) and it was generally an issue discovered based on how the power was ran.


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