radio noise

[atpbean32]

Hello All:
I have a noise problem that I require help with. I’ve researched the problem but became more confused on what to do. I hope someone can help. Below I have listed the symptoms and my equipment.
Symptoms:
1) No noise with ignition off.
2) Noise with ignition on-engine not running.
3) Noise with engine running.
4) Noise does not change with engine speed, It is a constant sound.
5) No noise with coax disconnected from radio during #2 or 3.
6) Also I get sporadic noise with the engine running and standing still or driving down the road. It will read
up to ½ on the signal strength meter.
7) Noise does not change in with speed of the motor or truck. It is a constant sound.
Equipment:
Truck: 2006 Freightliner Century Class S/T has fiberglass body.
Radio: Connex 3300 hp.
Microphone: Road King 56B.
Coax: Belden RG-8X 14’-11/2”.
Mount: Firestik stainless steel mirror mount and stud.
Antenna: Wilson 2000 with 10” extension.
Power is connected to the battery terminal at the fuse box.
Ground is connected at the windshield post.
Ferrite core (snap on one’s) are used on coax & power cords.
Magnum power filter is also used..
I have all good grounds and continuity in the antenna system.
SWR is as follows:
CH1 1:5
CH19 1:3
CH40 1:2
Any advice would be greatly appreciated.

[2xR]

Electric motors have a frequency. They don't intend to transmit, but, they do. When you turn the ignition on an electric motor starts to operate and the radio is receiving it's signal.

When you disconnect the coax, the radio looses the receptor needed to hear, or receive the transmission. If it were 12v interference, the antenna wouldn't be a factor because the buzz would be getting in the radio via the power source, or ground.

I don't know exactly which electric motor is the culprit, but, I'd be looking at electric fuel pump, some ventilation fan, or maybe even the ECU.

I too operate a 'Shaker. I just gave up and pretend that every day is a bad ground noise day.

[james henry]

I had the same problem and sent my power staight to the battery away from the fuse box. I grounded straight to the chasis and all my noise went away.Hope this helps and keep on trucking.

[ka3vvv]

The Noise can come from your fuel injector or your ECM. I have a Caterpillar motor on 20m 40m & 80m I get an S 7 noise. I may have shielded my fuel injector wires of try some ferrite beeds and RF chock. In see what happen.