Mobile radio receiving interference in vehicle

[kb3pbr]

I have just recently installed a Vertex FTL-1011 low band in my Chevy S-10 Blazer and I am receiving a lot of interference. I think it is the something with the vehicle causing the interference because when I turn off the vehicle the interference goes away. I also get the same interference with a low band portable when in the vehicle. I have the radio powered with 8g wire directly to the battery, so the radios power source doesn't pass through the vehicle electrical system. Is there any thing I can do to get rid of this, or at least reduce it, this interference is quite frequent and very annoying. Any assistance would be greatly appreciated.

[mdulrich]

Saying interference is like painting a masterpiece with a 6 inch brush, it covers a lot of area at once. You need to be more specific with what you are hearing.

Mike

[Retired911Guy]

I had the same problem with 87 S10 Blazer with my scanner, just a few channels (un-PL'd) sounded like they had birdies on them until I shut the engine off.

Probably the Ignition Computer Chip. Unless the noise goes up and down with your engine rpms, then the alternator

That would be my guess, really nothing else in the vehicle would emit RF (computer chip), or direct electrical interference (alternator).

Ignition chip -> maybe trying to shield it somehow, I think it's mounted on the firewall somewhere, but it's been a long time since I climbed under the hood of that truck. (that would be the "old truck" listed in my sig, "new truck works fine with un-PL'd) channels)

And if the alternator, I'm sure you know there are alternator noise elimination kits you can buy, although the effectiveness of remains unsure to me. On smaller alternators I think they work fine, but in my yrs in working on and listening to Fire Engines (large meaty alternators) we had some that never had alternator whine and others had we could NEVER get rid of it.

Hope this helps some
Dave

[kb3pbr]

Thanks 911Guy... As for the sound, it is a very quick burst of static, about half a second in length that happens extremely frequently on random frequencies.

[fineshot1]

Year ago I purchased a new car(ford tempo) and I installed my ham gear and had similar noise.

Poked around and started disconnecting stuff while the car was running and came to find out
it was the digital clock in the dash board. I pulled the dash panels off and permanently pulled
the plug on that pos. I also had some noise from the cars computer but there was nothing I
could do about that and had to live with it.

[stateboy]

What year Blazer and what engine?

What is your antenna mount? If it's not an NMO mount through the body, what is it? A poorly installed antenna is the first place to start.

-Check the OE ground straps. Replace the one from the engine to firewall with a 3/4" ground STRAP or larger. Ground the hood and tailgate to the body.
-Replace the spark plugs, plug wires and ignition coil (there is no ignition "chip"). Get RFI-surpressed plug wires.
-Check the OE grounding points on the engine. GM likes to have several on the engines that corrode over time.
-Have the alternator load tested. If it fails, the rectifier diodes are likely shot. This has been the source of many RFI issues.
-Check the routes you ran the power and control cables. Stay away from the PCM and associated wire harnesses.
-Check and clean the battery terminals and any underhood OE power points.
-Ground the radio to a beefy chassis point somewhere near the radio. Do not run the ground out to the battery.

Lowband is a tough place to track down RFI issues, but it's not impossible.

[kb3pbr]

It is a 1995 with a 4.3 liter Vortec engine. My antenna is an NMO mount, although its on a magnet mount. My reason for this a is because I wanted it high, on the roof, but did not want to drill holes in my roof. I really don't think it is an antenna issue, because as I mentioned I have the same interference issues with a portable on the same band as the mobile. I will look into the items you mentioned, although some of the items seem a bit extensive, seeing I'm not very mechanically inclined.

[Retired911Guy]

Originally Posted by stateboy

What year Blazer and what engine?

-Replace the spark plugs, plug wires and ignition coil ------> (there is no ignition "chip")

.

I've been tuning up my own vehicles for 45 yrs, the 87 s10 Blazer has electronic ignition, that means a computer chip controls the ignition.

According "HAYNES" Automotive repair manual for 1982-1993 S10 PU's and Blazers, "The CCC (Computer Command Control), controls the following,

Feedback Carburetor Sensor
Electronic Spark Timing
Electronic Spark Control
Air Management
Exhaust Gas Recirculation
Transmission Converter Clutch
Manual Transmission Shift Light
Air Conditioning Clutch

It goes to say "one might think that a system that uses an on-board COMPUTER would be difficult to diagnose..... then tells about the "check engine light" and the plug where you plug in the special computer reading device and the computer tells you where the problem is".

The Computer Command Control (that controls the ignition and other as noted above) is located on the firewall upper far left side. It appears that only 1/3 of it extends into the engine area, the rest appears to extend into the dashboard area near the grove box.

Don't discount the CCC as a problem area, with it extending into the dash board area and the other functions it does, it could be the source of the problem. and I say COULD, not it is!

Dave

[stateboy]

Originally Posted by kb3pbr

It is a 1995 with a 4.3 liter Vortec engine. My antenna is an NMO mount, although its on a magnet mount. My reason for this a is because I wanted it high, on the roof, but did not want to drill holes in my roof. I really don't think it is an antenna issue, because as I mentioned I have the same interference issues with a portable on the same band as the mobile. I will look into the items you mentioned, although some of the items seem a bit extensive, seeing I'm not very mechanically inclined.

It's very possible that the magnet mount antenna could be part of the issue, as the antenna mount is not grounded to the body. However, since you mention the noise is present on a portable as well then you need to find the noise source first.

Does the noise vary in pitch as the engine is rev'd or is it constant?
Is the noise a whine or is it pops that sound like static bursts?
Try the blower motor at various speeds...does that change anything?

Answers to these questions will help narrow it down.

Originally Posted by Retired911Guy

I've been tuning up my own vehicles for 45 yrs, the 87 s10 Blazer has electronic ignition, that means a computer chip controls the ignition.

According "HAYNES" Automotive repair manual for 1982-1993 S10 PU's and Blazers, "The CCC (Computer Command Control), controls the following,

Feedback Carburetor Sensor
Electronic Spark Timing
Electronic Spark Control
Air Management
Exhaust Gas Recirculation
Transmission Converter Clutch
Manual Transmission Shift Light
Air Conditioning Clutch

Comparing your 1987 Blazer to his 1995 Blazer is comparing apples to oranges. Your 87's "CCC" as it's called is more than a "chip". It consists of several IC chips and other parts to form a rudimentary computer that oversaw various parameters in a shielded box. It was "dumb" in the sense that it only read certain sensors and could throw up a warning light on the dash. Could the CCC cause RFI? Possibly, and there is no arguement there. Your calling it a "chip" is misleading and not a proper description.

The PCM (powertrain control module) in the OP's 1995 Blazer is a sealed unit mounted under the hood that actively controls the engine and transmission by overseeing and adjusting several dozen parameters. It has no relation to the rudimentary system in the 1987 Blazer. Can the PCM cause RFI? Possibly, especially on lowband...but a bad ground, bad alternator or worn ignition components is more likely.

What say you, OP?

[dd364]

Wrap your power wire with tin foil.I never tried that but it might shield it.

[Magnetsteve]

I used to get alot of interference on my Motorola CDM1250 from my satellite radio... dont know why, when I turned off the satellite radio it would stop..

[Retired911Guy]

Originally Posted by stateboy

Comparing your 1987 Blazer to his 1995 Blazer is comparing apples to oranges. Your 87's "CCC" as it's called is more than a "chip". It consists of several IC chips and other parts to form a rudimentary computer that oversaw various parameters in a shielded box. It was "dumb" in the sense that it only read certain sensors and could throw up a warning light on the dash. Could the CCC cause RFI? Possibly, and there is no arguement there. Your calling it a "chip" is misleading and not a proper description.

Just doing my best to mislead people by referring to the electronic ignition as the "Ignition Computer Chip" while it was really called the CCC and didn't have one chip, but several chips. So EXCUSE ME!
(by the way, when I posted my reply to the original poster, he had yet to state what year his Blazer was, so there were NO apples or oranges. AND you admit that it could possibly be the cause) Sounds to like you're pounding your chest and want to be the alpha male. Please go right ahead.........

To: kb3pbr, I'm sorry I mislead you, hope stateboy can fix your problem.

New Sig:
The intentional misleading and not a proper description member.

[torrespi]

K ... everybody all has some good point ...they sell "plugs" that can help reduce radio nosie ..you may want to consider that for you problems along with the other ideas ...Good Luck !

[nickcarr]

Originally Posted by kb3pbr

I have just recently installed a Vertex FTL-1011 low band in my Chevy S-10 Blazer and I am receiving a lot of interference. I think it is the something with the vehicle causing the interference because when I turn off the vehicle the interference goes away. I also get the same interference with a low band portable when in the vehicle. I have the radio powered with 8g wire directly to the battery, so the radios power source doesn't pass through the vehicle electrical system. Is there any thing I can do to get rid of this, or at least reduce it, this interference is quite frequent and very annoying. Any assistance would be greatly appreciated.

Might try one of these...

NS1535: Antenex (Laird Technologies) Blackhawk Noise Suppressor 35 Volt 15 Amp

[popnokick]

Disconnect the antenna from the Vertex. Turn the radio on, open the squelch if necessary. Is the noise still there? Then it's probably coming in through something other than the antenna (DC power line, external speaker wire if you have one, etc.). Is the noise gone when you disconnect the antenna? If so, then it's definitely an RF noise source coming in via the antenna, cable, or connectors. Don't bother troubleshooting alternator whine or other sources that enter through the DC power source. Focus on the antenna/RF sources using the suggestions in this thread.

[torrespi]

I agree ... great advice !