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Therealporkchop
Intermediate Member
Username: Therealporkchop
Post Number: 339
Registered: 11-2002
| | Posted on Tuesday, August 16, 2005 - 11:42 pm: | 
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OK, I've ask this before and I'm at it again...
In my truck, 2004 Sterling LT9513, truck has fiberglass doors. It came with factory co-phased antenna's on the mirrors. The coax has a splitter or combiner on it so that the FM stereo uses these antennas instead of the truck having a regular FM stereo antenna. I completely unhooked the FM from them and run ONLY my XM radio.
The truck cam with fiberglass whips. I tossed them in favor of Wilson trucker 2000's. Using the factory mounting locations, I can get a perfect flat SWR. If I put my own mirror mounts on the mirror brackets and install the Wilson's, I can't get a good SWR. Not usually lower than about 2.5 or higher. So I now use a Wilson 5000 mag mount.
Now here is the problem. I can turn on my stereo and key my radio. The CB comes across the speakers in the truck. This happens whether I use the 5000 or 2000's. On the 2000's I drop about 4 S units on another station when we are both still. Switching back to the mag mount, my signal increases as does my receive. On either I have the feedback problem. The more power I run (IE an amp) the worse the problem gets.
If I have my Yaesu and Magnum on at the same time, which ever I key up causes interferrence on the other radio. If I have my stereo on which has a sub box in the truck with amp, the Yaesu will cause the woofer in the box to "thump" when I key it up.
The S9 is hooked straight to the battery. The Yaesu is hooked up the post inside the dash where the fuse blocks are. They are suppose to be straight sources. The amp for the stereo is also hooked straight to the battery, but the truck has two and the S9 is on one and the Pioneer amp is on another. They are tied together though. The amp is grounded to the bolt that holds down the passenger seat.
The antenna, I've added a ground wire to it and it's hooked to the bolt that holds the cab visor on. I just added a small box to the S9 and it increases the feedback and interferrence when on.
Does anyone know what the deal is and how to fix it? |
Tech808
Moderator
Username: Tech808
Post Number: 6701
Registered: 8-2002
| | Posted on Wednesday, August 17, 2005 - 12:07 am: |
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Therealporkchop,
I have posted this several times before on the Forum here.
#1 ~ Run DIRECT to the Batteries + for power and NEGATIVE to the Batteries or Frame for All Radios and Amps.
#2 ~ Run Ground wires from your antenna brackets, DIRECT to the FRAME.
#3 ~ DO NOT use any in dash or inside tractor wiring for anything except what came Factory wired in the truck.
#4 DO NOT use any factory installed Wiring or Fuses for any Radios or Amps.
#5 NEVER USE AN ANTENNA SPLITTER FOR ANYTHING!
We had to do this with our Petes and KW's, and Freight Liners and had NO PROBLEMS. 
The trucks are designed from the factory for 4 watt radios and use the Cheapest Wiring, Coax and Antennas they can find.
Slap a barefoot cobra / uniden in one and you may get lucky and maybe not and the performance of Factory antennas and coax STINK!
And Sirus and XM Radios can interfere with your CB Antennas and you can get deedback thru them.
Jaybird_od CEF #557 had to move his Antenna for his S-9 to the Center Rear of the Tractor to avoid feedback after he installed a Sirus system
Just our Personal Experience and hope this helps.
Lon
Tech808
CEF808
N9OSN
PS: We ran our (Old Style)2970DX with the Big Heat Sink in all of our trucks with No Problems.
Jaybird_od and Wrongway both CEF members run the S-9s in day cabs (Slip Seaters) and drive for 2 different trucking firms and have No Problems after following my advice above.
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Nobodyknows
Member
Username: Nobodyknows
Post Number: 67
Registered: 4-2005
| | Posted on Wednesday, August 17, 2005 - 12:19 am: |
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Turn off the stereo when you talk on the cb... Ok but yeah, you can try using shielded wires for your speakers, i've read about that one in a different forum and it worked on this problem.
It's going to be trial and elimination here, I'd start with removing the pioneer amp from the system and bypass it with speaker wires. Now test with a key up. This will tell you if it's the amp picking up rf or if it's the XM radio unit. No luck? try shielded speaker wire fron the XM to the speakers. if that helped then replace all the speaker wires with shielded and try it.
Also try grounding the pioneer direct to the battery. Also try and get that amp far away from everything else as possible. You have alot of testing to do. |
Alsworld
Advanced Member
Username: Alsworld
Post Number: 947
Registered: 1-2002
| | Posted on Wednesday, August 17, 2005 - 1:03 am: |
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I am completely unfamiliar with big rigs, but wonder if maybe shielded speaker wire may help in this situation?
It's a thought to consider, and cheap (provided you have the time to invest your own labor).
Just an input for consideration to the forum. Any thoughts on whether this sounds logical? Big wheels are not my specialty.
Alsworld |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 1248
Registered: 7-2004
| | Posted on Wednesday, August 17, 2005 - 8:04 am: |
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buddy's beer-hauler GMC with sleeper cab showed good swr's & performance w/connex & dx250.
new tractor was daycab, same swr's, but HORRIBLE performance, squeal w/power mic, etc etc. mfj259 showed different then paradynamic wattmeter-threw on a bird, swr's 1.5 or a bit higher, yet REFLECTED watts was at 50%. antennas were TOO close to trailer now causing high reflect/poor performance. used factory mirror mounts, changed coax & angled forward, swr's stayed 1.5, reflect dropped to 6-7% & all was well.
companion used LARGE amp, took out gps & computer 1st day... |
Chad
Intermediate Member
Username: Chad
Post Number: 391
Registered: 11-2004
| | Posted on Wednesday, August 17, 2005 - 9:33 am: |
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Sometimes shielded speaker cables can do more harm than good, causing amps to oscillate, etc. this cable is more intended for transformer coupled amps in HV paging systems. Pay careful attention to input gain structure, if you can bring it down a tad and run the head unit harder then that will help. High quality line level cables will help also. When I say High quality I don't necessarily mean high dollar. I switched to gepco 61081 foil shield cables with switchcraft connectors and it solved my problems, just not "show quality"  You can get paired version of this it's 61802. 61801 retails for 20 cents a foot and is available where they do higher caliber A/V installs.
Are you using a good quality RF coax?
Chad |
Therealporkchop
Intermediate Member
Username: Therealporkchop
Post Number: 340
Registered: 11-2002
| | Posted on Wednesday, August 17, 2005 - 5:27 pm: |
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OK..to start..I had these problems before I installed the stereo amp or the XM. I had this problem with the factory stereo. I changed to a Pioneer CD player, added the amp and sub-box and threw in a pair of dome tweeters. The XM I added first to the factory system.
But like I said, I had the problems before. The coax on the factory setup stinks. I think it's RG58U or something close to that. The Wilson mag mount has the stock coax on it as well, so whatever came on it, is what it has.
I did have the radio grounded straight to the battery and it still is. Had the problems started after I installed the XM or stereo parts I would lay it to them and remove them. But it was already there. I also had the antenna ground I added ran to the chassis.
SO where do we go from here?
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Hollowpoint445
Advanced Member
Username: Hollowpoint445
Post Number: 674
Registered: 6-2004
| | Posted on Wednesday, August 17, 2005 - 7:46 pm: |
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It sounds like strong RF is getting back into the cab - perhaps because the cab itself isn't enough of a counterpoise for the antenna(s).
What is the cab of the truck made out of? You said the antennas are mounted on the mirrors - where are the mirrors mounted - the fiberglass doors? Are the cases of your radios grounded to the body of the truck? How?
A radio shop near me often uses a 4' fiberglass whip as a counterpoise when the cab is fiberglass. He tunes both antennas with an analyzer until the VSWR is good on 19. Basically it's a shortened dipole and I'm told it works great even though it looks a little odd. If you use a whip that's similar in color to the cab it blends in at a distance. |
Therealporkchop
Intermediate Member
Username: Therealporkchop
Post Number: 341
Registered: 11-2002
| | Posted on Wednesday, August 17, 2005 - 11:59 pm: |
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The cab is steel. The doors are fiberglass. The truck came with factory dual fiberglass whips, had the same problems. The mirror mounts are metal mounted to the fiberglass doors.
The antennas on the mirrors are hooked to the factory coax. It's still run up throught the truck, yet they aren't hooked to anything inside the truck. Should I remove or atleast unhook them?
Should I get a good ground strap and ground the cab to the chassis?
Would switching over to a tri-mag mount help any at all? Mostly thinking of doing this because of hitting tree limbs and knocking over my antenna all the time.. |
Hollowpoint445
Advanced Member
Username: Hollowpoint445
Post Number: 676
Registered: 6-2004
| | Posted on Thursday, August 18, 2005 - 7:07 pm: |
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The tri-mag mount will help keep your antenna in place, but I doubt it'll help your RF problem. I think a hole mount would be better if you can stomach the thought. Also consider a center or top load antenna to get the coil as high as possible. Most of the signal is radiated at the coil and the farther away from the cab the better for your problem.
I think what you're looking at here is the fact that the doors are fiberglass and don't offer any shielding. The RF just gets right inside your cab, and the more power the worse it'll be. I don't really know how to fix it short of lining the doors with foil to create a good shield. |
Boatman
Junior Member
Username: Boatman
Post Number: 12
Registered: 3-2005
| | Posted on Thursday, August 18, 2005 - 8:26 pm: |
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plenty of rf zooming around in truck wiring. not only do you have antennas outside, youhave antennas inside, too. |
Therealporkchop
Intermediate Member
Username: Therealporkchop
Post Number: 346
Registered: 11-2002
| | Posted on Thursday, August 18, 2005 - 8:30 pm: |
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Maybe I should try lining them then, hadn't thought of that. I've been thinking of getting the tri-mag mount and using a Wilson trucker so I could move the coil up higher. Unless there is a way to move the 5000's coil up higher? |
Bigbob
Senior Member
Username: Bigbob
Post Number: 2149
Registered: 12-2001
| | Posted on Sunday, August 21, 2005 - 12:03 pm: |
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Something else you might try,get some bronze or copper screen cloth and fiberglass resin and mold the screen cloth to the interior of fiberglass hood doors may be a problem,then bond a good heavy ground wire to cloth and apply resin,when dry you will have at least a shielded engine compartment and a huge ground plane.The rf is getting into wiring in engine compartment with roof mount,through glass with mirror mount.If you look straight down on roof mount and see any fiberglas or glass the rf is getting in there.Bigbob |
Therealporkchop
Intermediate Member
Username: Therealporkchop
Post Number: 352
Registered: 11-2002
| | Posted on Sunday, August 21, 2005 - 2:30 pm: |
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Cool, thanks. I'll have to look into trying that one. |
Vtwinn
Member
Username: Vtwinn
Post Number: 72
Registered: 8-2004
| | Posted on Monday, August 22, 2005 - 3:25 pm: |
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I had the same problem in my 379. with the uniden and the wilson 2000's no feedback at all. Put the 95t in with the roof mount 5000 and as almost better than the talk back ,when the stereo was on,LOL.I took the 95t out and put it in my jeep and no feed back through the speakers at all. Now I have a general lee in the pete and still the same prob as the 95t. My fathers has a new sterling and he has the same problem with his general lee, also when he keys up all the idiot lights on the dash come on. weird.
Bob
CEF544 |
Therealporkchop
Intermediate Member
Username: Therealporkchop
Post Number: 356
Registered: 11-2002
| | Posted on Tuesday, August 23, 2005 - 3:04 pm: |
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It's got to be a ground problem then. I'm going to get myself some good ground straps and ground every stinking thing I can.
And if that doesn't work, then I'll burn it and collect the insurance and go get that KW I was looking at to begin with HAHAHAH! |
Gumball
Junior Member
Username: Gumball
Post Number: 49
Registered: 10-2004
| | Posted on Tuesday, August 23, 2005 - 5:36 pm: |
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Tech808 has the answer (as usual) I had similar problems with a Volvo 770.
First, ground EVERYTHING:
-antenna brackets to cab
-radio and amp chassis to cab ground
-cab to frame
-battery neg. to frame
-alternator bracket to frame
Second, run new (and seperate) co-ax. With the Volvo, I just ran one to the passenger side, and used a Predator 10K antenna. I left the drivers side coax in place, and used it as a scanner antenna.
It was some work, but WOW, it was worth it! |
