RF noise problems

[Fatpretzle]

I have my radio in a 93 dodge ram 3/4 ton. I have a firestick antenna mounted at the rear end of the cab. I have a uniden pro538w with a 100w linear and I have a severe problem with static. It only happens when the engine is on. I have installed a rat-shack power filter, grounded my tailpipe, moved radio ground all over the truck including bat, replaced coax, and I still have a noise. I know it is coming through the antenna because I unplugged it and the noise went away. I have my swr to about 1.3. It is kind of a ticking noise that fallows the engine RPM's. It only happens when the engine is on and it is not the fuel pump because I don't hear it when I turn the key. What else can I do? I am frustrated because I can barely hear when the truck is on!
Thanks,
Fatpretzle

[doughnut]

kinda almost sounds like an ignition noise?

[Fatpretzle]

That's what I thought. But what can I do about it?

[doughnut]

I'm not sure but maybe reroute anything and everything that goes to your radio that's close to your coils, spark plug wires and plugs..ect.? I'm honestly not sure, but I'm sure someone else would have an idea.

[231]

The Pro series radios don't have alot of filtering (unfortunately). That alone may be the problem.

If you unplugged the antenna at the radio and it went away, that indeed is pretty likely it's from the antenna system. What happens if you disconnect the antenna leaving the coax hooked up? Do you hear it at all (even a little)? If so, switching to a better quality coax may help...at least RG8x (Beldon or better). Lots of guys run that crappy RG58U with low shielding and run the coax under the dash near the wiring harnesses. Sometime RFI from the ignition system can travel through the harnesses and inside. So route the coax totally away from the dash area if you can.

Just a couple thoughts. Let us know how it goes.

[Seminoles]

Going on the assumption it is a gas engine have you changed the plugs and spark plug wires lately also check around the coil at the wire for sparks at night or very early morning if these are fine then it is the injectors you can use these [Please login or register to view this link] on each one as close to the injector as you can get them on each one TBI would be four one for each of the two wires to the two injectors for SFI would need eight one injector for each cylinder put them just behind the plug on the intake at the injector also check the ground on the ECM (computer) the injector drivers can cause this popping too there transistors just like the drivers in your radio some just slide into place with a metal tab scratching into the case just slide it out and back in to clean the contact area.

[dud muck]

I have my radio in a 93 dodge ram 3/4 ton.

1993.. That would rule out Coil Over Plug, you must have spark plugs with ignition cables.

I have installed a rat-shack power filter, grounded my tailpipe, moved radio ground all over the truck including bat, replaced coax, and I still have a noise.

Since you said your swr is 1.3:1, i would think your antenna is grounded pretty good. I mean the ground connection of your SO-239 jack to your truck-bed chassis. Its also good that you grounded your tailpipe. I would also make sure your truck-bed is grounded to your cabin with the braided strap. Since the truck is 14 years old, i would take a look at the grounding strap between the engine block and the chassis, and replace or refurbish it. And do the same for the battery (-) to the chassis, because they age over time. These things can help both transmit and receive.

231 has something there.. using a better shielded coax might help if its being picked up by your coax more than the antenna is picking it up. As a last resort, you can RFI shield your ignition wires as described on the k0bg website, its alot of work though.

[Fatpretzle]

Where exactly are the grounding straps I should be looking for?

[dud muck]

Where exactly are the grounding straps I should be looking for?

maybe somebody here knows your particular truck, but on my car its a silver braided strap between the engine block and the firewall.
You'll just need to poke around with a flashlight.

The battery strap is easy, it should be right on the negative battery lug.

These items could be considered wear items like battery or tires. Although i would like the think they would be good for ten years.
Metal can corrode and degrade over time (rust), but may only be noticed on the radio. If you find they look nasty, you might be able to clean them and solder them. But even if you buy new, you should sand-paper the mounting points on the chassis.

but also try the coax test that 231 mentioned.

[Fatpretzle]

Well i unplugged the antenna from the mount and all the noise disappeared. I looked around for a strap from engine block to chassis and could not find one at all. The engine mounts provide no grounding because they are rubber and there is no metal to metal contact. The battery to chassis looks good. I also could not find a ground strap to go from the bed of the truck to the chassis but the bed is bolted directly to the frame. The chassis rides on rubber body mounts and I'm not sure where its grounded. Does anyone know where the ground straps are on this particular vehicle (particularly the block to chassis) ?

[Seminoles]

Well i unplugged the antenna from the mount and all the noise disappeared. I looked around for a strap from engine block to chassis and could not find one at all. The engine mounts provide no grounding because they are rubber and there is no metal to metal contact. The battery to chassis looks good. I also could not find a ground strap to go from the bed of the truck to the chassis but the bed is bolted directly to the frame. The chassis rides on rubber body mounts and I'm not sure where its grounded. Does anyone know where the ground straps are on this particular vehicle (particularly the block to chassis) ?

Should be around the back of the manifold one of the bolts to firewall could be just a 10 to 12 gauge wire should be black unless someone changed it you can always just get a battery cable with eyes on both ends bolt one to the engine (not an exhaust bolt) and the other to the frame.

[dud muck]

Well i unplugged the antenna from the mount and all the noise disappeared.

I suppose you did that because it was simpler than unplugging the coax from the antenna? well good, thats done.

I looked around for a strap from engine block to chassis and could not find one at all. The engine mounts provide no grounding because they are rubber and there is no metal to metal contact.

Well there has to be something there. I am no auto mechanic, but maybe somebody else here familiar with engines might tell you that without one, your engine might not run well. It certainly doesn't hurt to add one, and it will definitely help your radio interference, just google for "engine ground strap" and see if your local auto parts store has one. just find mounting points on your engine and chassis so you know how long it needs to be.

I also could not find a ground strap to go from the bed of the truck to the chassis but the bed is bolted directly to the frame. The chassis rides on rubber body mounts and I'm not sure where its grounded. Does anyone know where the ground straps are on this particular vehicle (particularly the block to chassis) ?

The truck manufacturer only adds the necessary grounding to run the electrical devices, such as lights or pumps.
The braided strap (for RF ground) you need to add yourself. The whole point is to provide a low impedance path from your antenna mounting point to the entirety of your vehicle chassis which contains your passenger cabin and engine. Make sure the antenna mounting itself is from from corrosion and insulating paint, not sure myself if your 1.3 vswr guarantees that. If the rubber mounts are blocking the ground path, you need to add braided straps at those points. And just because your bed is bolted down may not necessarily mean its a low impedance RF path, yet i would try strapping whatever is blocking the passenger-engine chassis to the truck-bed first.

the ground strapping will help both transmit and receive.