Noise at 42.xxx Mhz

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Bill3

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I have searched and searched for my answer, so please if I have missed the answers, point me in the right direction.

I have had a scanner for years Uniden BCT-7. Never could pick up Missouri Highway Patrol - 42.060, etc, I had to lock them out due to noise/interference. This has gone on through at least 4 vehicles (all chevy trucks if that matters). I had not tried real hard to find the source other than moving power wires and antenna wires around some. I just assumed that maybe the old (and possibly cheap - can't remember) scanner was to blame. So, I thought I would buy a new "state of the art" scanner and that would cure my problem plus get me back into scanning. Well, brand new Uniden BCD-996T and same problem. I really like the scanner (and the challenge of programming, etc - I will get it someday).

I think I have eliminated it to alternator noise, but can't seem to find the proper cure. By the way, this is a diesel truck this time with the same whine/noise as the previous trucks that weren't diesel. And the noise goes away above about 1500rpm. I can unplug my outside (magnet mount Radio Shack - of some sort) antenna and put the little one that comes with it on and the noise is the same.

Any and all help or guidance is greatly appreciated.

Thanks,
Bill
 

W4UVV

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Prince George, Virginia--Central Va.
Alternator filtering

A whining audio that changes pitch in direct relationship to you accelerating/deaccelerating is a good indication your RFI is in part alternator sourced. Private email me giving your email address. I will scan a two page magazine article that discusses how to filter the alternator, electronic gauges and coil RFI and send them as email attachments.
 

rcvmo

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Romulus, Mi.
well, Unfortunatley, with these new cars having so many computers in them, it's hard to tell where the noise may be coming from. Make sure your antenna is grounded. If on the trunk, run a ground strap from the arms that support the trunk to the body of the vehicle. Does it happen when the car is running or not? Keep in mind too that most scanners have a wide front end allowing them to cover vast portions of thelow-band, so any computer generated frequency, harmonic will lock on a channel in a heartbeat.
A while back, I had a Dodge 600 ES. I could stall the engine if I programmed my old Icom ICU 16 to a certain 440 MHz channel and recieving while the HT was just sitting on the front seat. Installing an external antenna took care of that problem.
Good luck.
rcvmo
 

Bill3

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Kimberling City, MO
rcvmo said:
Make sure your antenna is grounded. If on the trunk, run a ground strap from the arms that support the trunk to the body of the vehicle. Does it happen when the car is running or not?
rcvmo
Only when running, from idle up to about 1500rpm.

What is the proper way to ground a mag mount antenna. Just grounding the panel it is sitting still won't get between the paint and antenna. Or maybe that is good enough??? Also, I had ruled out the grounding of the antenna further due to the fact that when I attach the provided telescoping antenna (granted in the cab) I still had the same problem. I am probably wrong, but trying to learn and solve.


Thanks for the replys.
Bill
 

mike_s104

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if you know the sub-audible tone for the service, set it. not sure if the scanner you have will do that though. I have about 10 PC and a bunch of TVs and stereo equipment at home. the 42MHz band used for State Police here is always noisy. I knew everything was causing interference but not until the power went out for a few hours and I noticed there was NO noise anywhere. funny how that works.
 

SCPD

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I had the same proplem with the 40's in my car house.
I parly could listen to the California chp freq. without somthing in my house or car causing really bat interference.
It al stoped when i changed from serching the PL tones to the used Pl tones
 

Bucko

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My Silverado's on board computer has always put un-wanted RF in the low band area as well as in the high band. The scanners will lock on to the RF signal generated from the computer then I can hear ignition noise or alternator whine. No matter where I had my antenna it would not help. Using a PL tone does help with my 96, example is there is an RF signal at 154.43 and using the tone makes it usable.
 
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fireside

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Tama IA.
You might try a alternator capacitor. I used to have one that you put inline with the + wire,the other lead was grounded to a good ground. The part is made by Standard Motor Parts # RC-13. Alot of automotive parts stores carry that brand. It took the ALT. whine out. I had to use it in my old 75 Chevy PU. Now i've got a FORD PU and no noise at all on the PRO2096 hooked up direct without the filter.
 

Bill3

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Kimberling City, MO
Okay, I have tried using the PL tone as a temporary fix with no results. I wonder if the interference I have overcomes the PL, or if the PL I am using from the database is incorrect.

Thanks again for the input. I'm still working on it.
 

fireside

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Tama IA.
Just another thought. You might try relocating your coax and or + wire. They might be picking up trash from one of the computers in cab.
 

sacscan

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Sacramento, CA
Bill3 said:
Okay, I have tried using the PL tone as a temporary fix with no results. I wonder if the interference I have overcomes the PL, or if the PL I am using from the database is incorrect.

Thanks again for the input. I'm still working on it.
Try listening to the affected freqs in CTCSS/DCS Search mode with the truck off. When the PL pops up on the screen you can program it in so the scanner only stops on that freq when the State Police transmits.
 

Bill3

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Sep 26, 2006
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Kimberling City, MO
I had a strange occurrence, or coincidence tonight. I heard nothing on my way home tonight, yet as soon as I shut the truck off, the State Patrol was broadcasting. So, I think I have the right PL programmed. Do you think it is possible that I could have so much interference that it is overcoming the PL tone?

Thanks again for all the input,
Bill
 

KE4ASQ

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Dixie Land (The South)
WHCA-mobile to WHCA-base, This subject is on to us, Execute Plan RE-EDUCATE, repeat execute Plan RE_EDUCATE, Ooopsss Forgot to use my DES_XL encryption.
*Laughs*
 
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