Injector noise on transmit only - 2013 F150

[WRQJ559]

I have been struggling to suppress injector background noise (low pitched buzz that changes intensity with RPM increase) on my 2013 F150 ecoboost (steel body) that occurs only on transmit. No noise on receive. 

My antenna setup is a midland MXTA26 mounted on a comet nmo front fender mount using pro58au coax cable (USA made). SWR reads about 1.0 to 1.5 depending on frequency.

My radio is a wouxun kg1000g plus and I used the factory provided wiring harness run from the battery through the passenger fender cavity away from vehicle harnesses down under the passenger footwell to the wiring access hole under the footwell carpet. Positive is at the battery, negative is at the same grounding point on the inside fender that the negative battery cable attaches to so the ford BMS hall sensor is not bypassed. I used quality copper crimp on terminals at both points. 

My first effort to suppress it I tried cheap Amazon ferrite beads of unknown mix on both antenna coax and power leads. They helped some but didn't solve it. I returned them and ordered the Palomar engineering troubleshooting kit beads containing mix 31, 75, and 61 covering a lot of frequencies. This kit hasn't arrived yet. 

I also tried putting a Powerwerx LF-1 DC noise suppressor on the power cable and it had no effect. Returned it. 

Thinking I have a ground loop isolation problem I then proceeded to place bonding straps on each hood latch and also at 3 places along the exhaust (exhaust tip, between muffler and catalytic converter, and before the catalytic converter with no effect. 

One item of interest. I connected my handheld kg935g to my truck's antenna coax with so239 to sma adapter and when that radio transmits with the vehicle running, the ignition noise on transmit is not present.  So it appears to be on the power side. 

So my question is this, which ferrite mix is likely going to be most helpful out of the 3 types I have coming and given my symptoms would I want to target the DC power only or would it also be smart to choke the coax with multiple turns as well?

Also, would it be worth my time to continue trying to bond more truck body parts? 

And lastly, could having an older battery with decreased cold cranking amps be contributing to my issue due to voltage drop even though when running the truck is on alternator power? And related to that, should I think about moving up to 10 AWG wiring making my own harness instead to help with voltage drop?

[tweiss3]

Unfortunately that antenna location leaves your feedline open to interference from noisy injectors/computer hardware. What cable is used between the radio and mount? Is it a double shielded? You could try to wrap the cable in the engine bay in aluminum foil (and add a bond strap to the body) and see if it helps. 

Another thought is check the grounding strap between the block and body. I've heard of that coming loose/corroding out and causing RFI issues. 

Next steps would be to start throwing money at it to bond everything, ground everything, etc. You likely will be better off drilling the hole and roof mounting the antenna. 

[WRQJ559]

16 minutes ago, tweiss3 said:

Unfortunately that antenna location leaves your feedline open to interference from noisy injectors/computer hardware. What cable is used between the radio and mount? Is it a double shielded? You could try to wrap the cable in the engine bay in aluminum foil (and add a bond strap to the body) and see if it helps. 

Another thought is check the grounding strap between the block and body. I've heard of that coming loose/corroding out and causing RFI issues. 

Next steps would be to start throwing money at it to bond everything, ground everything, etc. You likely will be better off drilling the hole and roof mounting the antenna. 

Good call on inspecting the block ground strap, stuff is getting crusty under there on an 11 year old truck. 

My coax is usa made rg58, 12 feet long. Marked pro58au on the jacket. It's strange that when I use the handheld on that antenna, even with the truck running no noise is there on transmit. It's only my mobile radio on the truck power wiring that gets the RFI. 

[tcp2525]

On 1/9/2024 at 11:40 AM, tweiss3 said:

Unfortunately that antenna location leaves your feedline open to interference from noisy injectors/computer hardware. What cable is used between the radio and mount? Is it a double shielded? You could try to wrap the cable in the engine bay in aluminum foil (and add a bond strap to the body) and see if it helps. 

Another thought is check the grounding strap between the block and body. I've heard of that coming loose/corroding out and causing RFI issues. 

Next steps would be to start throwing money at it to bond everything, ground everything, etc. You likely will be better off drilling the hole and roof mounting the antenna. 

Definitely a grounding issue. My suggestion is to also ground the bases of the NMO trunk lip mount. I have a 2013 F150 with the EcoBoost lawnmower engine as well, but I punched holes in the roof, so no issues. The Lincoln had the NMO trunk lip mount on the front hood and I had all my wires and cable in the engine compartment and no noise. The strap will eliminate the noise. 

 

[WRQJ559]

More data points gathered today. Trying to isolate the problem area I hooked up my mobile radio to a separate power supply (in this case a dakota lithium battery). With the truck running there is zero noise on transmit. Again proving (I think) that antenna is fine, but power is noisy. 

I also did a second experiment, this time I hooked up the radio to truck power but ran an alligator clip test lead wire from the radio body to the seat bracket. The noise reduction on transmit was significant. Not eliminated but significant. Might try this same experiment again but with a wide braided bonding strap and see if even more noise is suppressed. This method combined with a toroid on the power lead might lick it. Just waiting for the toroid to arrive. 

What conclusions would you make based on these experiments?

[BoxCar]

Back in the 70's I tackled my power noise on my CB using a pi filter. It's an axial feed capacitor with bleed resistors on the input and output leads of the capacitor. Fixed all the power issues,

[SteveShannon]

1 hour ago, WRQJ559 said:

More data points gathered today. Trying to isolate the problem area I hooked up my mobile radio to a separate power supply (in this case a dakota lithium battery). With the truck running there is zero noise on transmit. Again proving (I think) that antenna is fine, but power is noisy. 

I also did a second experiment, this time I hooked up the radio to truck power but ran an alligator clip test lead wire from the radio body to the seat bracket. The noise reduction on transmit was significant. Not eliminated but significant. Might try this same experiment again but with a wide braided bonding strap and see if even more noise is suppressed. This method combined with a toroid on the power lead might lick it. Just waiting for the toroid to arrive. 

What conclusions would you make based on these experiments?
 

I would agree that your power appears to be noisy. Whether it’s the ground or the positive or both is difficult to know from here. 
My conclusion is that you’re doing all the right things!

[WRQJ559]

Back in the 70's I tackled my power noise on my CB using a pi filter. It's an axial feed capacitor with bleed resistors on the input and output leads of the capacitor. Fixed all the power issues,

This will be my next step should all else fail with bonding and ferrite use. I was discussing dc to dc isolator devices with an electrical engineer friend today that should "nuke the noise from orbit, it's the only way to be sure".

[tcp2525]

12 hours ago, WRQJ559 said:

This will be my next step should all else fail with bonding and ferrite use. I was discussing dc to dc isolator devices with an electrical engineer friend today that should "nuke the noise from orbit, it's the only way to be sure".

The F150 power is general pretty clean. If you are sure it's the injectors you might have an underlying problem that might leave you stranded one day. Generally you have a few choices for noise, alternator, ignition, and/or injectors. I would definitely go the way you are doing and clean the power up, but don't rule out finding the cause. Sometimes you just can't fix it and masking the issue is the only alternative. Good luck.

[WRQJ559]

Update: My final solution was to throw a 30ah eco-worthy lifepo4 battery under the seat and now I have excellent quieting on transmit. Complete power isolation from the vehicle is the ticket.

After extensive A/B testing with the various common easy solutions for filtering the DC power nothing ever stopped it and I had a lot of false positive placebo effects going on with various attempts.

One thing that did seem to knock down the harshness of the buzz was putting x2 2200 micro farad capacitors in parallel after an mfj1142 filter (only used the filter to provide some resistance for testing, it didn't work by itself) The capacitors smoothed out the tone some. I could potentially continue to experiment with capacitors and target specific frequencies if I were to figure out the specific frequencies of the noise using an oscilloscope. But I'm so happy with the lifepo4 performance I may not pursue it further unless I get bored.

Stuff I thought about trying but didn't:

- Making my own power leads with heavier gauge wire as the theory is that voltage drop can increase conducted noise. Just didn't feel like re-running wire.

- Further troubleshooting and cleanup of the various DC grounding points on the engine and frame (I did try HF style RF bonding of the hood and exhaust, which doesn't seem to matter for conducted DC noise for UHF, wasted effort)

- The extreme of replacing injectors and injector harness. Nah, they work.

[Socalgmrs]

I just saw this post,?didn’t see it before.   Ive built off road trucks and jeep electrical systems for over 30years.  I’ve installed 1000s  of cbs, stereos, ham and gmrs radios.  This sounds like a ground issue of some kind.  Motor, frame, body, alternator, ect.   If you wired straight to the battery and you still have problems something is not right in the truck and may become a problem in the long run.  

[WRQJ559]

I just saw this post,?didn’t see it before.   Ive built off road trucks and jeep electrical systems for over 30years.  I’ve installed 1000s  of cbs, stereos, ham and gmrs radios.  This sounds like a ground issue of some kind.  Motor, frame, body, alternator, ect.   If you wired straight to the battery and you still have problems something is not right in the truck and may become a problem in the long run.  

Yep, I should probably inspect and clean each ground strap and the connections to the alternator at a minimum. It should be noted the noise isn't extreme and I can functionally communicate using the radio it's really just an irritation. Also the leads are connected positive to the battery post and negative to the same location on the inside of the engine bay as the negative battery cable so as not to bypass the ford BMS hall sensor. But yeah, even bypassing that common ground and going straight to the negative post didn't stop it. I did clean up the strap connections from the body to the frame on the passenger side really well because of the easy access and that one is known for corrosion issues.

[WRQJ559]

I just saw this post,?didn’t see it before.   Ive built off road trucks and jeep electrical systems for over 30years.  I’ve installed 1000s  of cbs, stereos, ham and gmrs radios.  This sounds like a ground issue of some kind.  Motor, frame, body, alternator, ect.   If you wired straight to the battery and you still have problems something is not right in the truck and may become a problem in the long run.  

@WRXP381 I would be curious to know if you agree that the noise sounds like injectors. After listening to the noise sample recordings on K0BG.com blog this seemed like the closest match.

Here is my latest test recording:

https://drive.google.com/file/d/10Oloo84FDnbdT4lqvJUbHP1CqDySZJ-G/view?usp=drivesdk