RFI Supression - ideas?

[Tinkerer]

 

[Stainless]

In many cases, it's a better idea to work on the grounds for your CB instead of the vehicle's other systems. How do you have the CB and VHF grounded? Do you have RF noise through the stereo, too?

I've read lots of stories where guys get power and grounds for their comm equipment directly to the battery instead of from the vehicle's electrical harness to solve noise problems, and it's quite successful. If I were you, I'd try running both temporary power and ground directly to the battery posts to see what happens before you spend a bunch of time adding suppression to your vehicle's systems. If that doesn't help, there are RF suppression coils available for stereos that can help the problems you're experiencing when added to the comm equipment power leads, too.

I see that you have an 04 -- in modern vehicles, there are so many different electrical devices that you may wind up tearing the thing apart before you find the specific one that's causing the most noise. Start simple.

[morerpmfred]

Had similar problem and though it was fuel pump as well but it turned out to be the wire supplying power to the coil. The rfi filter i purchased from radio shack eliminated the problem and it was installed to the [am fm] radio power supply wire . All radios where wired directly to the battery as well with the exception of the am fm radio. The noise only came through on the other radios when am fm radio was on. Most stereo installers should have filters for sale

[cLAY]

I wrapped my power lines for the CB in tinfoil and then electrical tape.  Seemed to work, very little noise. Maybe try wrapping the ant wire as well. Where do the antenna wires run? Do they run parallel to the pump wires at all? Even with the floor in between them?

[cLAY]

Is the roof rack properly grounded to the chassis?

[FiEND]

got a CB with ANL filter?  using a fiberglass antenna rather than metal whip?

princess auto sells good noise filters for a few bucks but like chasing ghosts.

[yyc_tbird_sc]

Check out either B&E Electronics, they're down in the south off of Manhattan Rd and Blackfoot Tr. They probably have what you need, or MRO Electronics in the NE just off 12th Ave north of 32Ave (the building behind Bolt Supply House).

Get yourself some 2 conductor 14Gauge shielded cable , and ground ONE side of it at the same place you have the radio grounded, ie at the battery. Run this to as close to your radio as possible and then put a torroid or ferrite in place there. This way your power cables are shielded all the way from the battery.

PS...IN THEORY: did you know that you can pick up those FRS/GMRS radios on a dual band ham rig? LOL

[cLAY]

Try a different radio. I'm NOT impressed with those all in one handsets. I had to repair one for a guy once after the internal grounding on the chasiss went bad(inside the little box). Not sure what happened or what I did but I got it working for him. We were on a road trip to Alaska and he had it in his motorhome. I think at the next stop he ended up buying a real radio.

There was someone in the Four Wheel Stampeders that had to send his in for repair as well, was broken out of the box.

[FiEND]

B&E is expensive as all hell... but good place.  MRO moved recently but still in the same general location so google them if you haven't been there in a while.

[cLAY]

Go to Road King, buy a Cobra 25 or Uniden 68(same thing). Have him do the $50 "tuneup". Ground the antenna mount and install a shielded power line. Then atleast you'll be starting off with decent equipment.

Gunther and I have similar setups, tuned Cobra 28s with good antennas installed properly and we can talk with one of us in Cochrane and the other at the Hwy 40 turnoff and 1a. Nothing for a Ham  I know but excellent for a CB.

[Elsifer]

For some reason, my Cobra 75 (all-in-one) works great, knock on wood.
I don't get any fuel pump noise (lucky, I know), just from the wipers, turn signals (odd, I know), and some other interior electronics. But then again, my cb is powered from the internal fuse block, I know, I'm lazy.

My VHF is direct from battery, and runs flawless, though there is some QRM/QRN picked up by the cb, when the VHF PTT is triggered when the radio is in ultra-high-power tx, 75w.

I do have to do some maint, check grounds, SWR, connector corrosion, etc. So I just might be in that zone of "if it ain't broken, don't touch it!"

I do plan on running my radio's off and direct power bus, power-poles or similar. But put noise filters on both the + and - leads for each radio.

It's not a perfect world, and sometimes we just have to deal with imperfections, and with radio, we deal with it the minute we turn the unit on!

[cLAY]

Thanks for the update. I though I read somwhere that you needed a area about 2 foot by 2 foot  for a decent ground plane. Although I know lots of people with antennas mounted on racks or sides of rigs and still get good reception. Gunther's rig comes to mind. His perfromance is about equal to mine and his antenna is an 8ft fibergalss antenna mounted on a ball mount out the side of the rear fender. Not sure what he has for a ground plane with a fiberglass top, maybe the whole tub? My setup is a 4ft wilson anteanna mounted pretty much dead center in the roof of my Grand Cherokee. With both run similar Cobra 29s and have talked to each other with me in Cochrane and Gun at the Hwy 40 turn off from hwy 1a. Pretty good for a CB I think but I'm always baffled how well his works as he doesn't even tune it. I even checked his SWR once and it was around 2-1 where as mine sits down around 1.1  .  I sometimes think SWR maybe over rated.

[cLAY]

There are also special antennas the require no ground plane. Often used on fiberglass RVs. You could also look into that.

[cLAY]

Mostly over my head but glad to hear you are making some headway. One note from a previous post, Gunther's antenna insn't a SS whip, its fiberglass and I think he gets it from Dean at the Road King.

Also maybe you can ansewer a question for me, I want to install cellular antenna on my Jeep for the Telus network. The research I did found that Telus operates in 800MHz range and the antenna kit I got says that for the 800MHz range I need to trim the antenna to 3" in length, seems pretty short to me considering that the way it comes its around 2 feet.

Do you know if 800MHz sounds right for Telus and does 3" sound right for an antenna at that range? Its a 1/4wave antenna.

[Hi Lo Silver]

I don't know if there's any difference what so ever in fiberglass or stainless steel. I've avoided the steel whip for one reason. The action of the steel whip after it hits obstacles on the trail. I never have liked the way the steel ones whip around looking for an eye to stick into. I do however think that the whip antennae is the only way to go though. I think you get the best reception from an antennae that's sticking out well above the vehicle itself. That's also why the roof mounts work well too.

The key thing to any antennae or any electrical for that matter is good ground. Most problems can be traced back to a bad ground. If any part of your anttennae mount are touching steel you're hooped.