Cobra Model 18 WX ST noise problem.
Kevin F. DeRose
minivan. I have been having a tremendous amount of ignition and
alternator noise with this radio. The noise is so bad that the
S-meter reads 5 at idle, and +20 at highway speeds.
When I turn off the engine, the radio is dead quiet. If I unhook the
antenna (Firestik FS 2 roof mount - yes it's grounded), the noise goes
away with the engine running or not. I have tried other antennas, but
the noise did not go away.
Is this a problem with this model or brand of radio, or is the minivan
the culprit, or both?
Because the problem is so bad, am trying to decide if it would make
more sense to fix the problem with filters, or just get a different
radio.
Any constructive comments or advice would be greatly appreciated.
Thanks in advance,
-Kevin DeRose
Hillbilly_1943
TAPE A QUARTER TO IT, THEN CHUNK IT OFF A BLUFF. NOW GO BUY A GOOD RADIO
!!!!
Kevin F. DeRose wrote in message <368d0619...@news.usaor.net>...
Truckracer
different circuit or go straight to the battery. Same goes for the ground.
--
Remove the nospam from the address to reply
Jay
noise rejection circuit in it. Most of the good mobile radios have a noise
blanker (NB) and a automatic noise limiter (ANL) that will reduce the noise to a
acceptable level, it will not cure the noise interference problem totally. And
yes the minivan may have a lot of noise floating around it, from the fuel pump,
ignition, engine control box, windshield wiper motor, and heater/air motor ect.
But you said that the noise level was S-5 at idle, and when to 20 over when your
driving, TILT! Something big time is wrong.
Suggested things to do:
1- Run the power for the radio directly from the battery. Both positive and
negative wires. Make sure you don't have the positive wire riding against the
metal body anywhere. I use a old piece of garden hose to protect the wire when
going thru the firewall
2- Verify the antenna is working properly, do you have a low SWR? Are you
getting out to other local CB stations?
3- Just because you think the antenna is grounded, it may not be. A lot of guys
here have reported that the mobile antennas mounted to a luggage carried just
don't work. They have a added a ground wire from the luggage mount the the
vehicles metal body, to insure a proper ground connection.
4- If after all this, and you still have the noise, I would suggest a better
radio.
5- A good friend of mine went into a CB shop and told them to install a good CB
Radio and would pay the last half of the money only after seeing the radio
installation and listening the engine noise it had. The filters and time would
cost you a lot more that the radio did.
6- Another thing to look for, verify there's a ground wire or strap from the
ground connection on the engine to the body. I installed a ground braid wire
from the negative battery connection on the fender to the vehicles firewall, to
the hood, and this helped a great deal in reducing ignition noise.
Suggested reading: "The ARRL RFI Book" Practical Cures for Radio Frequency
Interference. Available at ham radio stores. Let me know if I can help anymore.
Jay at jay...@ptw.com .... In the Great Mojave Desert, just down the road ah
ways from the fillin station.
Bedula
> I recently installed the Cobra Model 18 WX ST CB radio in a GMC
> minivan. I have been having a tremendous amount of ignition and
> alternator noise with this radio. The noise is so bad that the
> S-meter reads 5 at idle, and +20 at highway speeds.
>
> When I turn off the engine, the radio is dead quiet. If I unhook the
> antenna (Firestik FS 2 roof mount - yes it's grounded), the noise goes
> away with the engine running or not. I have tried other antennas, but
> the noise did not go away.
Have you tried other antenna mount points? Is the coax of good quality?
Sometimes rerouting the coax does the job since it might be going right
past an RFI generating device like a fuel-pump. Make sure the excess coax
is properly wound into large (16"+) oval loops and not into small
circular ones.
> Is this a problem with this model or brand of radio, or is the minivan
> the culprit, or both?
Not the best radios for sure, but your problems seem too excessive to
just blame the radio.
> Because the problem is so bad, am trying to decide if it would make
> more sense to fix the problem with filters, or just get a different
> radio.
Before you try filters, try to run the power from other points. If you
aren't already doing it then run direct to the battery. Some people have
had good luck running the power to the battery with twisted-pair wire.
Use a good solid wire if you do this and add a 20A fuse to the red+ wire
just before the battery. After all that, then yes, try an external noise
filter. The kind for a stereo system will suffice.
RadioDoc37
I'm here in Simi Valley and have a cabin up in Wrightwwod.....always going thru
that Mojavi desert.
Take care
Mike "Troubleshooter CH11 "
ML781120
if it is hook up to battery try your fuse box
if it is hook up to the fuse box try to the battery
if they don't work try to your cig lighter
if that don't work I don't know but if you find out how to get that out another
way write me
back and tell me becuse I am having the same
thing
thank you
martin
ml78...@aol.com
Handy Andy
On Fri, 01 Jan 1999 17:44:01 GMT, While trying to figure out how to
get the Mouse out of the Furnace, The Monitor, displayed an idea about
"Cobra Model 18 WX ST noise problem." from 'kfde...@usaor.net (Kevin
F. DeRose)' and the Keyboard responded with this:
:+> I recently installed the Cobra Model 18 WX ST CB radio in a GMC
:+> minivan. I have been having a tremendous amount of ignition and
:+> alternator noise with this radio. The noise is so bad that the
:+> S-meter reads 5 at idle, and +20 at highway speeds.
:+>
:+> When I turn off the engine, the radio is dead quiet. If I unhook the
:+> antenna (Firestik FS 2 roof mount - yes it's grounded), the noise goes
:+> away with the engine running or not. I have tried other antennas, but
:+> the noise did not go away.
:+>
:+> Is this a problem with this model or brand of radio, or is the minivan
:+> the culprit, or both?
:+>
:+> Because the problem is so bad, am trying to decide if it would make
:+> more sense to fix the problem with filters, or just get a different
:+> radio.
:+>
:+> Any constructive comments or advice would be greatly appreciated.
I've got questions about what's missing in the message. This post is
geared towards helping you to help us find an answer to a problem
you're having.
Please understand that it is hard to fathom the solutions to the
problems when theres a lot of grey area. Hopefully the following will
help guide you...
Well, you've got a radio. It's only got ANL though, hows the radio
mounting in the Minivan?
Is it "in" the dash, or sitting in-between seats, or on one of the
seat cushions next to you? These are not the most ideal, or best ways
to use the radio. One quick stop, and the radio bounces all over the
place and possibly damage you, the trim, or the radio itself.
Power connections, how are they connecting to the battery? Ciggarette
lighter? No, thats' a noisy spot. Fuse block? Well, try tapping the
Radio Fuse, it may help by having the AM/FM/Vehicles' intergrated dash
radios power supply on the same supply line, helping to make the
receive quieter. But, the noise exists only when the antenna is
connected. I'm thinking that this is either an antenna, or location of
radio too close to the noisy sources, or lack of ground type of
problem.
Ground? You say you're using a Roof mount, does this mean that you've
already drilled a hole? Hmm... Or are you using a Mag mount?
Antenna...it's pretty short. It's not a stellar performer with such
small, or short in, height. These antennas are more prone to pick up
noise due to the way they work, and lack of ability to "capture"
signals your radio is trying to receive. They pick up signals, but not
the ones you are trying to listen to, well enough, for the radio to
actually pick out and amplify the CB'ers signals. This type of
antenna, not the brand, the height being so short, makes this antenna
unuseable for Mag-mounts or for stuffing a radio in-between the seats
or console without a good ground connection either for the antenna or
the radio itself.
Ground in a radio is a funny thing, there's RF ground, and then power
supply ground. You don't have both with a Mag-mount antenna, or if the
radio is simply sitting in a console without the case, being mounted
electrically and physically, to the vehicle.
If the radios' in the dash, you have all the accessories located right
by it. And it the radios' own bracket [which helps supply RF ground
when it's mounted to the vehicle, and the radio mounted to the
bracket.] not being, as not disclosed in your message, used to mount
the radio, makes this a hard post to try and answer the problems
you're having. Having the radio so close to these accessories and
having no idea as to how it's mounted, I can only guess that moving
the radio *away* from the dash might improve the signals with less
noise masking them out.
It could be something simple as a shielding problem. Or it could be a
location of the radio too close to the other accessories, or the power
supply is from a noisy battery supply source. Like a ciggarette
lighter, or poor ground connections, causing a shielding problem.
A WORD OF WARNING!
No matter what brand, or features, the radio you might want to change
this radio over to, will NOT solve your problems 100%. You are only
treating a symptom, not finding a cure.
There are hints outlined above to help guide you to find the correct
answer, or a direction to take, in trying to use what you have before
you waste more money on a supposedly better radio that may not solve
your problems unless you fix, or correct, the ones outlined above
first.
Regards!
:+> Andy <+:
CCCC BBBB ##
. C C B B ##
... You're on your way to being a CB'er when... C BBBB ##
,.. You use a Bumper Sticker that reads... C C B B
... CB! We known 'em, we love 'em! CCCC BBBB ##
Paul Christensen
You have given enough info for a good start at the trouble
shooting process
.
First: under the assumption that you know
the difference in the sound from noise sources we'll go
with the ignition and alternator systems, as the problems.
Second: You need to know how the noise is entering your
radio system.
1- Wiring ..... power, audio, other ???
2- Grounding problems
3- Air bourn via antenna system or other.
You say the problem goes away when you disconnect the
antenna system. If this be the case, look behind door #3
(Air bourn entry) first. There is a very small chance the other
two, may be the cause and a little greater possibility
that one or both are contributing to it.
It sounds like you have an excellent noise transmitter with your
vehicle and an equally top notch noise receiver with your radio
system.
Proper filtering or shielding can go along ways in reducing
entry via Wiring or short range Air bourn noise. In your case,
this is not at all a logical starting point.
Solid grounding and the elimination of ground loops throughout
the vehicle are sometimes the cure for a problem like yours.
I sill would not start here.
Set aside filtering, shielding and grounding for now. I would
suggest that even a "better radio" would end up being unsatisfactory.
With the severity of your noise, S9 +20 db, it would most likely
have to be a radio that has not been invented yet. Even a $200 - 300
noise killer radio and a similarly priced audio DSP would, most
likely leave you wanting.
Your noise appears to be entering the radio via the antenna connection by
way of the coaxial assembly, the antenna mount or (most likely) the antenna
itself. If this be it, entry is Air bourn from a relatively high power
transmitter(s) ..... your car's ignition and alternator system(s) or what ever
turns up as the source of the noise. Unless your willing to replace the
car with one that does not have these problems, you must kill the noise
at it's source !
Grounding problems are pretty much an animal unto themselves and
may not be related to noise entry via Wiring or antenna. Noise entry
by Wiring maybe filtered or shielded out, without the need to kill it at
it's source. The noise is still there but just does not enter that device any
longer. This is usually the easiest/cheapest problem to fix. Grounding
problems with the radio/ant system are most often second in
simplicity/cost. Next, full and proper vehicle grounding can be a real
bear, but good trouble shooting can reduce grief here also. Sometimes
the best or only thing to do, is re bond every ground in the entire car.
If the source of the noise must be fixed, a loose connection/ground or
two may be all there is to it. Finding them may be the biggest chore.
On the other hand, more costly repairs and/or replacements of vehicle
components, may be in order.
At this point Kevin, good trouble shooting, demands that we take a few steps
back. First, try to define the noise source. Is it ignition, alternator and/or
other ??? If your not sure of what your hearing get the ear of a good car
radio or audio installer to help you identify the noise sounds. Once your
pretty sure of the source take a look at and around those devices.
If you find any bad or loose Wiring, connection, grounds, ect., fix them if
their quick, easy and cheap. If so and the noise is gone, your done.
Well done ! Give yourself a pat on the back and get on with life. :-)
If your still reading, get prepared to really dig into it. It may take a few
more steps and an hour or two, all the way to a few days and a few $$$.
Don't despair, chances are it won't break the bank, but in the rare case,
shrink it noticeably. Just to play it safe at this point, find out if this is a
common problem with this make, model, year, ect. and if so, is there
a known fix(s). Can you find anyone with the same type Van. If so,
get close to their rig with yours, turn your motor off while theirs is on.
Open the other Van's engine compartment and get it as close to your
antenna as possible. Talk to others with Vans and/or radios like yours.
Talk to dealers .... car and radio. Talk to installers and repair tech's.
If it looks practical to continue the trouble shooting, you must confirm
the entry point of the noise into your radio. Going on what you have
said, Air bourn entry via the RF (ant) port seems most likely.
NOTE: Trouble shooting from afar is difficult at best. Even with your
fairly detailed description of the problem, it's hard to beat a voice
question and answer session or two. The Q&A would provide more
and better detail. I'll do my best with what I have to work with.
1- Provide an alternative power source for the CB radio, Like a
separate battery. Keep the power leads short. Wrap any excess
lead wire into a bunch. Get the battery in the Van or take it and the
radio outside and to the back of the Van.
With the antenna system connected to the radio, start the motor
and turn the radio on. If the noise is still there, it is almost certain
that it is entering the CB through the antenna system. In the unlikely
event that it is gone or greatly reduced it may be a combination
of problems with wire and air entry and/or ground(s).
2- If you have a AM broadcast radio in your Van, does the noise
show up there also? If not, then the above mentioned rare combo
problem may be it. Unplug the antenna on the AM radio. Does the
noise go away like it did when you did the same on th CB ? If you
can provide an alternative power source to the AM radio, run that
test also. There are a lot of other factors that can enter the equation
at this point. way too many to cover here, without the results of tests
preformed thus far.
3- When your near other cars, do you cause interference to their radio(s) ?
If you do, Air bourn entry gets another vote. Check it out. Be creative and
try different things. Move radio, wire, coax ....everything around. You have
a very short antenna with a lot of wire coiled on it .... that can make a better
noise probe than a desired signal antenna. You should try a different,
known good coaxial assembly. I'd look that antenna mount ground over
real close .... maybe re do it or move it all together. If your willing
to mount at or near the rear of the vehicle, your noise may go away or
go down. A 1/4 wave steel whip as far away from the engine may do it.
The idea here is to get the noise entry point (ant) as far away from the
noise source as possible. Also, a base or center loaded 50-60" steel whip
could be better than the open load, on that shorty that you have now. If you
can try these things without too much hardship, one just might pay off.
4- The very best fix is always the originating source. Often it turns out to be
the quickest and cheapest. Rarely it may not be cost effective. On occasion this
sort of fix will take the talent of a noise finding pro and or a good mechanic.
Killing the noise at it's source can and most likely will have some valuable
bonus to it. Reception on AM and/or FM radios will almost assuredly clear up
also. Engine performance and/or gas mileage may improve. With the fix, a
waiting disaster may be averted. Depending on the cause(s) and the resulting
fix(s), many possible extras could come out in the end
To track the noise source down yourself, your going to need a "Sniffer".
Commercial units are great if your doing it for a living, but in your case
improvision is called for.
Sniffer #1 -- If the noise shows up on the AM broadcast band too (almost a
sure bet), take a dirt cheap AM pocket radio and start sniffing. Start the van,
turn on the pocket radio and move in and around the Van. Start outside
the rig, go to all four sides at varying distances and note the change in noise.
What's it like at the rear of the vehicle ? Next, probe the inside of the rig.
Be sure to check in and around the dash. Next, open the engine compartment
and start a close and detailed scan in there. WARNING watch out for moving
parts ... fans, belts, pulleys and the like. This is not a time for lose clothes
or unfocused minds. To better pinpoint the source, you must reduce the
sensitivity of the radio. The noise will be strongest at the top of the band
(1600Khz) so tune down lower to 600Khz, if need be. For more reduction
in sensitivity, try wrapping one or more layers of tinfoil around the radio.
Ear phones/head phones could be helpful or a must with the tinfoil or a loud
motor.
Sniffer #2 -- If the noise is not on the AM band a CB radio will have to be
used. The pocket radio can make a great 'Far Range' probe and a
properly equipped CB, a good 'Near Range' sniffer. The best CB based
noise sniffer is a Hand Held with a analog 'S' meter, headphone jack and
BNC antenna connector. Take the antenna off and put a 3-6 ft lenth of coax
in it's place. The far end of the coax should be striped to the center conductor
for about the last six inches. Be sure the center and shielded don't short out.
DO NOT transmit with this lash-up. Tape this end to a 1-2 ft stick, with the 6"
exposed end of the coax taped over at the far end of the stick. The near end
is used as a handel for your six inche probe. Now get in there and track that
noise source down to the closest point possible. Keep an eye on those coax
and headphone cords in that engine compartment. The 'S' meter will show
the smaller changes in the noise level.
5-- Really give the areas where the noise is the strongest, a good look,
poke and pull. You may see or feel something suspicious. It may be a
deeper problem and require the help of a noise or automotive Pro.
Ignition noise can be caused by cheap or defective spark
plug wire(s), Distributor cap, roter, points, condenser, ect., ect. or their
more modern equivalents.
The alternator could have bad diodes, a defective winding, ect., ect..
Track it to as defined a point as possible.
Take care of the obvious.
Try the Quick, simple and cheap next.
Finally look at the deeper possibilities.
Well Kevin the Suns coming up and I'm getting fog in my head.
That's about all I can do for you right now. If you can get back
to me with more/new info, I could take you farther. I would
really like to know how things go for you on this project.
Good Luck and bye for now.
\\///............................Tube's
On Fri, 01 Jan 1999 17:44:01 GMT, kfde...@usaor.net (Kevin F. DeRose) wrote:
>I recently installed the Cobra Model 18 WX ST CB radio in a GMC
>minivan. I have been having a tremendous amount of ignition and
>alternator noise with this radio. The noise is so bad that the
>S-meter reads 5 at idle, and +20 at highway speeds.
>
>When I turn off the engine, the radio is dead quiet. If I unhook the
>antenna (Firestik FS 2 roof mount - yes it's grounded), the noise goes
>away with the engine running or not. I have tried other antennas, but
>the noise did not go away.
>
>Is this a problem with this model or brand of radio, or is the minivan
>the culprit, or both?
>
>Because the problem is so bad, am trying to decide if it would make
>more sense to fix the problem with filters, or just get a different
>radio.
>
>Any constructive comments or advice would be greatly appreciated.
>