Tombo

I am an idiot apparently. I have been trying to install my new Cooltech license plate mount and need some help. If I check my SWR with just the plate frame and mount I am getting readings of 1.6 on 1, 1.1 on 19, and 1.6 on 40. All readings that would be just fine. Once I button up the install my readings go to hell -- 2.7 on 1, 1.9 on 19, and 2.8 on 40. It is almost as if I am getting bad reflections from the light housing. I do not have tail light guards that might interfere.

I have now done this 4 times with the exact same results. I have added a 4 gauge flat braid ground strap to the frame from the mount w/ no changes to SWR readings.

I am banging my head against the wall and don't know where to go. Any help/ideas would be appreciated.

zeppo

Have you got any of the coax bent rather tight, maybe some is getting pinched when you reassemble the mount. There's a chance you've perforated the shield on the cable with one of the plate screws as well. And I don't think it would make that much of an swr problem but avoid coiling any excess coax as it induces voltage in itself and creates more magnetic intereference, same magnetic lines of flux theory at work in the windings of your alternator.

I remember tucking everything in that mount became a pain, especially since i had it apart half a dozen times looking for grounds that didn't exist because i didn't know how to tune my antenna.

edit: if you haven't already check out rightchannelradios.com. They have a few tips and tricks and understanding swr stuff for newbs like us.

Tombo

Update... I'm not crazy!

So the problem seems to be coming from the vehicle's electrical wiring. If I have it all buttoned up and everything connected properly my SWR on 1 and 40 are very close to 3. If I have it buttoned up with the brake wiring not connected, I am at 1.8 on ch1, 1.2 on ch19, and 1.8 on ch40.

How do the brake wires being plugged in change my SWR??

Help!

JK-jeepit

I want to say it's your ground. But you did say you had a ground going to the frame..
Is your power coming from the battery?
this could be a good one.. If I think of anything.... I'll post it.

Tombo

Yes. 1" wide tined flat braid ground strap from back of the washer/bolt on the Cooltech mount directly to the frame. The radio power is directly to the battery and ground is to the bolt on the passenger side which is directly tied to the battery.

zeppo

Interesting. I really don't know what to you tell you. I even have some of my brake wiring sharing a common loom with the antenna wire at the tailight and have no such issues. Maybe the brake wire(s) are chafed and causing some weird feedback through one of the nearby groundstraps? I don't even know if that's really possible, just thinking it out on the page.

I haven't looked in there since I installed mine but I would also suspect the plate light shorting to the antenna or coax could be a concern.

Good luck. Subscribed.

JK-jeepit

So when I was doing my radios I noticed that the ground strap to the engine block was a very thin strap that I could see through. It's possible that the ground is loose or even damaged. If you can install another ground strap from your engine to the frame.
Alot of RFI is caused by poor grounding. I'm not saying this is the problem but it's a place to look.
it's worth a try.

Tombo

Any tips/pictures on where to add a secondary ground strap? I looked for about 30mins and couldn't figure out a very good spot.

Thanks,

Tom

OH9JK

Are you checking with the antenna cap on and all your doors closed?

Tombo

Yes, all doors/windows/tailgate/tire carrier are closed and the vehicle is in an open area with nothing in close proximity. The only changes from good to bad SWR are when both of the tail light harnesses are connected.