Engine Noise

[PugCity]

Hello Everyone!

I'm new tot this forum! (Thanks Google)! How do you eliminate engine noise on the CB other then just using the noise block/squelch built in the radio? Is there something other that I can do to help with the engine noise, other then cutting the engine off? Although not excessive at all...just a little annoying. Special kind of spark plugs in the engine? Noise Filters etc?


Thanks,

Pug City

 

[KevinC]

Moved to the CB forum for better visibility and it isn't location specific,

 

[a417]

Ten thousand vehicle specific locations, ten thousand individiual tried and true solutions...it's a hunt. Identify, remediate, lather rinse repeat.

What'll really frost you is when you're working on a fleet of identical radios in identical vehicles, and one has alternator noise, one has fuel pump noise, one has coil noise, one has driver induced noise, etc.

Everyone on here has a brother who is a master mechanic who graduated from NASA after building the Apollo lander, and built their own vehicle after inventing combustion propulsion, so YMMV.

 

[PugCity]

Sounds easier to just shut the truck engine off. and use the old squelch button/noise blocker.

Pug City

 

[SouthernRoller]

Is the noise entering through the electrical connection, or through the antenna?

 

[PugCity]

I believe the electrical connection. Hooked directly to battery in vehicle...
When engine rpms increase so does the whirring sound in the buzz.

Pug City

 

[KK4JUG]

Get a filter for the power line. Google "automotive electrical noise filter" and you find all kinds of choices,

 

[Project25_MASTR]

Easy way to help diagnose. Disconnect the antenna and see if the noise is still there (don't key obviously). If it is, then the noise is coming through the power run.

I had a Midland mobile that had that problem once upon a time. I switched to a Cobra and the problem went away.

Best way I've found to run power is direct to the battery and ground to chassis (not the negative post). Now, can you get noise doing that, yes. Next options would be trying a clamp on ferrite on the power lead and then a noise suppression filter.

 

[PugCity]

What is a clamp on ferrite?

 

[UnidenBC92XLT]

https://www.rfparts.com/chokes-inductors/chokes-ferrite.html

 

[mmckenna]

Best way I've found to run power is direct to the battery and ground to chassis (not the negative post). Now, can you get noise doing that, yes. Next options would be trying a clamp on ferrite on the power lead and then a noise suppression filter.

This has worked well for me on some installations. Had this issue with a VHF mobile radios in 2005 or so GMC Canyon/Chevy Colorado pickups. Powering directly (+ & -) off the battery put a lot of noise on the transmit audio. Moving the negative lead off the battery and to a body ground nearby solved the issue.

Also:
Do not rely on the negative power lead for your radio ground. Run a short jumper from the radio chassis directly to a nearby chassis ground.

 

[PugCity]

Thanks. Right now it is connected direct to battery ground. Will ground to frame. Hopefully that will stop it. Without a filter.

 

[SCPD]

Ten thousand vehicle specific locations, ten thousand individiual tried and true solutions...it's a hunt. Identify, remediate, lather rinse repeat.

What'll really frost you is when you're working on a fleet of identical radios in identical vehicles, and one has alternator noise, one has fuel pump noise, one has coil noise, one has driver induced noise, etc.

Everyone on here has a brother who is a master mechanic who graduated from NASA after building the Apollo lander, and built their own vehicle after inventing combustion propulsion, so YMMV.

I had my good laugh for the day with the ending.

 

[beamin]

Put a potato in the exhaust pipe or turn the volume knob all the way to the right.

I once heard that you can put a small non-polarized cap across the alternator to reduce it. I think the value was in the nf range. Try playing with different values and see if you can narrow it down some.

 

[Project25_MASTR]

Put a potato in the exhaust pipe or turn the volume knob all the way to the right.

I once heard that you can put a small non-polarized cap across the alternator to reduce it. I think the value was in the nf range. Try playing with different values and see if you can narrow it down some.

Usually you see that done on the radio side for a homebrew noise filter.

 

[JayMojave]

Hello PugCity: Have you fixed the Alternator noise problem?

PKY said: Easy way to help diagnose. Disconnect the antenna and see if the noise is still there (don't key obviously). If it is, then the noise is coming through the power run.

I had a Midland mobile that had that problem once upon a time. I switched to a Cobra and the problem went away.

Great trouble shooting advice here, if the antenna is unplugged and you still have the noise its coming in thru the power leads. But more than likely its being radiated into the air from the Alternator Diodes turning on and off.

Years ago this was a big problem with CB Radios, Noise Blankers (NB), and quieter/better Alternators got better and cured most of this. How ever this noise problem pops up once and a while. Trying another radio is also a good call.

I use to make a Alternator Noise Filter that installs in between the antenna and radio. This of course for the Alternator Noise coming in thru the antenna. In a small metal box a 88MH Toroid Core with a 1 uF to .088 uF non polarized capacitor, wired in parallel, and in series with the RF path, fixed or significantly reduced the alternator noise. But this was again for the older radios of the 1960's and 1970's.

Let us know how your making out there....

Jay in the Great Mojave Desert

 

[prcguy]

Spark plug noise is usually airborne but can sometimes get into the electrical power leads. Spark plug noise is usually a popping or ticking noise at idle but becomes a whrrrrr at higher rpm. Alternator noise doesn't pop or tick and makes a whrring sound that changes with engine rpm. Alternator noise will often show up on transmit so have someone listen to your signal while you rev the engine as part of the diagnosis.

You need to first identify what kind of noise it is and there are other great suggestions in disconnecting the antenna, etc to help isolate the source. A single clamp on ferrite is of little use and at CB frequencies you would need to wrap at least several turns through a ferrite core or clamp on to even start to be effective and that will only address spark plug noise riding on the power leads. You need a much more serious inductor/capacitor filter in the power leads if it turns out to be alternator noise.

In the worst cases of spark plug noise I've had to put shielded braid over the spark plug wires but you have to be careful as this can change the vehicle timing.
prcguy
prcguy