| Author |
Message |
    
Jameslarson
Junior Member
Username: Jameslarson
Post Number: 18
Registered: 4-2006
| | Posted on Thursday, April 13, 2006 - 4:45 pm: | 
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This is very frustrating. I installed a power filter and put it inline in the radio. Still get engine noise (Noise goes up and down as engine goes faster or slower). When I disconnect the coax from the antennas SO239, the noise gets reduced about 90% (Can still slightly hear it). Get this though. When the antenna is connected, and I am sitting in my driveway, I can actually hear noise in my CB radio from other peoples car engine as they pass by my house. AHHHHHHHHHHHHHH...O yeah, why doesn't the ANL/NB work on sideband, only on AM. This is a 148 GTL 5 pin side mount. Thanks. |
Tech808
Moderator
Username: Tech808
Post Number: 9731
Registered: 8-2002
| | Posted on Thursday, April 13, 2006 - 6:51 pm: |
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Jameslarson,
Do you have the radio case/frame grounded to you car?
Not just connected to the mounting bracket but an actual ground wire running from the case of the radio to a good ground.
And are you sure that your Antenna is also grounded good?
What Make/Model of car and what Make/model of radio?
The more information you can give us the better chance we have of helping you to solve the problem.
Lon
Tech808
CEF808
N9CEF
CVC#2 |
Tech237
Moderator
Username: Tech237
Post Number: 277
Registered: 4-2004
| | Posted on Thursday, April 13, 2006 - 7:03 pm: |
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Another trick I have used in the past, is to run the power using two lengths of coax. Use the inner conductor to pass the power along and ground the braid at the battery end only. leave the end of the braid nearest the radio floating.
It is surprising, the first time you od, this how much nosie is suddenly gone, especially if you follow all the usual anti-noise methods too. |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1168
Registered: 6-2004
| | Posted on Thursday, April 13, 2006 - 8:31 pm: |
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Now you are receiving the noise through the antenna - at least most of it. The only way you'll get rid of the noise now is to use a noise supressor at the source of the noise - your alternator. I don't know if Copper sells such an item, but I know that GC or Gold Line makes one. Of course you could just use a capacitor to shunt the RF to ground at the alternator's output, but that might involve some modification of the wiring and if your vehicle is under warranty that's probably not going to be allowed.
The Cobra 148 GTL has an excellent noise blanker/automatic noise limiter. Has the radio been modified in some way? Installing a Channel Guard improperly can cause the noise blanker to function improperly. |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1336
Registered: 7-2004
| | Posted on Thursday, April 13, 2006 - 8:52 pm: |
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Tech 237, sorry to butt in here.
I'm interested in trying your method, but, the details are not sinkin in to my brain today.
Could you explain more step by step. Thanks |
Jameslarson
Junior Member
Username: Jameslarson
Post Number: 20
Registered: 4-2006
| | Posted on Thursday, April 13, 2006 - 9:08 pm: |
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Hi. Like mentioned in the original post, it seems as if it is coming from the antenna. Because if I diosconnect the coax from the antenna, most of it goes away. I have the radio grounded directly to the battery. Antenna is grounded great. I even sanded down the paint on the inside of the roof of my van so the disc hits bare metal. There are no shorts in the coax or antenna system as I have tested with a continuty tester. What is really weird like mentioned in the post, is that if I am sitting in my driveway, I can actually hear the engine noise from other peoples vehicles in my radio as they pass by. Weird.
148 gtl 5 pin side mount
Chevy van
Mini 8 coax
please help |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1428
Registered: 9-2004
| | Posted on Thursday, April 13, 2006 - 10:38 pm: |
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you either need to add the cap on the alternator, or try a new alternator, but the new one may make noise too.
best to try a "feedthrough" capacitor, which you would add to the positive lead of the alternator.
its your cheapest cure,
matt |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1337
Registered: 7-2004
| | Posted on Friday, April 14, 2006 - 12:36 am: |
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I just bought a brand new alternator as old one
was ready to bite the dust. Now, my whine is
worse with new Alternator. I have same problem
as you James. Not fun is it. I'll be setting back watching this post. Always open to new ideas
to try.
JIM/PA/CEF 375 |
Vanillagorilla
Advanced Member
Username: Vanillagorilla
Post Number: 527
Registered: 4-2005
| | Posted on Friday, April 14, 2006 - 9:09 am: |
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Try grounding the Chassis of the radio directly to your Vans chassis with as short as possible strap. I've heard less than 9" is preferable more than once. You could tie in your DC ground here as well...I would and did  . Then go to your battery and add a nice ground from it to the body of the van or firewall...again as short as possible.
My Power goes right to the battery but all my grounds stay as short as possible. That alone helped me with noisy static recieve, mic squeal and a vicious mic bite with the heater on!
Ground your 148 from one of the screws on the rear of the chassis to a suitable ground point AS CLOSE AS POSSIBLE. Even with this you will encounter noisey cars from time to time! Some vehicles just have noisey fuel pumps (Fords for one) and even noisey windshield wiper motors! All these seem to get worse in the rain....wiper motors OBVIOUSLY but traffic lights drove me nuts!
As for your own engine noise..alt whine...I still get that no matter what. My GrantXL is the only radio which totally blanks that out. Any other radio (current Magnum incl.) I still hear it with the volume turned all the way down...whirrrrr....Whirrrr! It amounts to NO "S" units but can be heard on quiet days.
You didn't mention which antenna you have? Just curious? Another thing..how familiar are you with this radio? Just get it? Has someone modded it for extra channels using the NB switch? Does it seem to make a difference AT ALL when switched?
One more time...BOTTOM LINE, Ground that chassis as short as possible. It will help to ensure the coax shield is grounded as well.
Good luck!
Hank CEF559 |
Bronzepony
Junior Member
Username: Bronzepony
Post Number: 44
Registered: 12-2005
| | Posted on Friday, April 14, 2006 - 4:01 pm: |
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A friend of mine was running a wilson 2000 mounted behind his cab on a 2 inch square tube. It had a solid copper ground wire run to the frame. He had engine noise. Today he installed a wilson 1000 roof mount right in the middle of the cab. Lost all of his noise. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 2698
Registered: 7-2004
| | Posted on Friday, April 14, 2006 - 7:05 pm: |
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changing the mount & replacing the crummy rg58 coax with 9913 eliminated 95% of the noise coming from passing cars & a lot of what was coming from my own.
the 'whirring' engine noise also was mostly eliminated. one day i heard it come back real bad, found the pl259 had loosened from the box, retightened it & whirring went away. couple weeks back the 'whirring' returned, as well as higher then usual reflect, checked connections again & found the shield had broken off from where it was soldered to the pl259. pushed it in tight, & got the rest of the day with no trouble til i could remove it & resolder. |
Jameslarson
Junior Member
Username: Jameslarson
Post Number: 29
Registered: 4-2006
| | Posted on Friday, April 14, 2006 - 7:57 pm: |
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9913?? Did you mean RG 213? Thanks. |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1339
Registered: 7-2004
| | Posted on Friday, April 14, 2006 - 8:03 pm: |
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Pat,
You using the thick coax in your vehicle???
Hummm |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1169
Registered: 6-2004
| | Posted on Friday, April 14, 2006 - 8:31 pm: |
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When I ran a 102" whip on my roof the ONLY noise I ever heard was from other cars because I used bypass capacitors to eliminate all of the noise coming from my own car. I could drive down the road with the ANL/NB off, windshield wipers on, fan blower on, and A/C on, and have no noise at all coming from my own car.
The only time I needed to use the ANL/NB was when other cars made it necessary. I could hear cars with high performance spark plugs coming from 100s of yards away. I HATE SplitFire spark plugs - they are the worst.
Changing coax probably won't do anything - at least it didn't for me. Why would it? At best it would only keep noise from inside of your car from being received. Anything that makes it outside would be received by the antenna anyway.
Addressing the noise at it's source is the best option. Bypass capacitors, feed through filter capacitors, or noise filters intended for the purpose are your best options. You could also try grounding the engine hood to your vehicles's body with braided strap across the hinges, but that doesn't always work with the way today's cars are designed and built. |
Jameslarson
Junior Member
Username: Jameslarson
Post Number: 31
Registered: 4-2006
| | Posted on Friday, April 14, 2006 - 10:34 pm: |
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OK.
1. Bypass capactitors. Where do I get them, and exactly how do I use and install them for this problem?
2. feed through filter capacitors???? Same questions.
3. Noise filters? If you mean the ones that go inline with the CB, I have done that.
4. I am at my wits end here. Please ehlp. Thanks. |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1172
Registered: 6-2004
| | Posted on Saturday, April 15, 2006 - 9:58 am: |
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Bypass capacitors are capacitors you install to bypass the RF to ground. Probably the easiest to use would be radial electrolytic, but you could use any capacitor. You want them to be 16 volts or more, and 1/2 a picofarad or more. Install them at the source of the noise (alternator, fan motor, windshield wiper motor, etc.) across the power wire to ground as close to the noise maker as possible following the polarity of the capacitor if any is specified.
Feed through filter capacitors are just a bypass capacitor in a case to make it easier to install. I used to buy them at Rat Shack for $5 or so, and they work great. To install them you mount them as close to the noise maker as possible, cut the power lead, and connect the ends of the wire to the filter capacitor. The first time I installed one I was trying to get rid of windshield wiper motor noise, and it got rid of it completely.
The noise filter I was referring to for your alternator isn't sold at Rat Shack. They're pretty large, and made to handle at least 100 amps. It's almost the size of a soda can, and the attached cable is 6 gauge wire. I know that gold Line makes something like that, but I don't know who sells them. |
Hotwire
Senior Member
Username: Hotwire
Post Number: 1166
Registered: 1-2005
| | Posted on Saturday, April 15, 2006 - 3:25 pm: |
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James, I use rg213 (thick stuff) in the mobile. Rids most noise I had. Also try mounting a condenser to the back of the radio and wire the pig tail into the postive power wire. The condenser will 100 percent stop any noise getting in that way! You can get a condenser at a parts store for a few bucks. 73 |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 2707
Registered: 7-2004
| | Posted on Saturday, April 15, 2006 - 5:18 pm: |
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yes i am 'warrior  . the skinny stuff would....ummm, well, not last too long
check members pics, it's a bit small, but you can see the 9913 under my predator |
Jameslarson
Junior Member
Username: Jameslarson
Post Number: 41
Registered: 4-2006
| | Posted on Saturday, April 15, 2006 - 5:37 pm: |
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A condenser? Can you be more specific? Sorry, I don't know what that means or exactly how to hook it up. Condenser to me sounds like an Air conditioner part. Thanks |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1342
Registered: 7-2004
| | Posted on Saturday, April 15, 2006 - 8:56 pm: |
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LOL...Pat- I have never tried the thick
coax in my mobile. Going to be doing a
different mobile install soon and will put
the thick coax on. What the heck! |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1433
Registered: 9-2004
| | Posted on Saturday, April 15, 2006 - 9:19 pm: |
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i think if someone could tell him exactly what value and voltage rating electrolytic capacitor to get, this would be the simplest route to try.
i would tell him if i knew but i dont. i would like to though!
matt |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1175
Registered: 6-2004
| | Posted on Saturday, April 15, 2006 - 9:52 pm: |
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"16 volts or more, and 1/2 a picofarad or more" |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1176
Registered: 6-2004
| | Posted on Saturday, April 15, 2006 - 11:15 pm: |
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Sorry - I should have written microfarad rather than picofarad. Greek letters aren't my strong suit.
On a capacitor microfarads are shown with the greek letter Mu which looks similar to a backward lower case u.
The value isn't particularly critical. Use whatever capacitor you have handy. I've read that any value from .1 microfarad and up will work as a bypass capacitor, but the lowest I've ever used was a .5 microfarad capacitor. The important thing is to keep the leads as short as possible so the RF is radiated as little as possible. |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1343
Registered: 7-2004
| | Posted on Sunday, April 16, 2006 - 12:16 am: |
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HOLLOWPOINT-
What's in those Alternator noise filters
they sell.??? They hook up to the Alternator. |
Hotwire
Senior Member
Username: Hotwire
Post Number: 1169
Registered: 1-2005
| | Posted on Sunday, April 16, 2006 - 10:17 am: |
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A condenser will work only for noise getting in through your power wires James. Go to the auto parts store and ask for one. Tell them what your going to do with it. A condenser is just one of the componets that is used in an older cars ignition system. This solution is a lot cheaper than buying a filter made for radios and works just as well. It will not hurt the radio. |
Tech237
Moderator
Username: Tech237
Post Number: 283
Registered: 4-2004
| | Posted on Sunday, April 16, 2006 - 10:17 am: |
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What happens if you leabve the coax connected but unscrew the antenna?
if the noise is still there then the coax is the culpret and needs to be replaced with a better grade one.
If the noise goes, then the antenna is the problem and it may pay to try a different type of antenna |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1178
Registered: 6-2004
| | Posted on Sunday, April 16, 2006 - 10:44 am: |
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I've never taken one apart to look inside, but I think they are large capacity feed through filter capacitors which are just a capacitor connected from the hot lead to ground in a package with connections that make it easy to install. Because of the large power ouput it's probably got a fairly large value capacitor in there to handle larger amounts of AC.
The model I bought at Rat Shack in the past was less than an inch in diameter and two inches in length, but could handle 40 amps. It had screw threads on either end with nuts to allow you to connect nearly any wire. Just cut the wire, strip 3/8" on both wires, and connect it to either end of the feed through filter capacitor.
The part numbers of Gold-Line filters that might help are 1080, AF100, 1090N/P, EF10. |
