Vehicle noise oddity

[hanlonmi06]

I've been getting more active with the ham hobby so I have been paying attention to, and making more frequent use of the mobile setup and I've noticed a lot of interference on HF. I've got the source narrowed down to the vehicle itself, and its primarily a problem above 10mhz (and for the purposes of this post, we'll leave it at HF).

I have an Alinco DX-70 through a diplexer into a Little Tarheel II antenna. DC power is straight off a fused line from the battery through the firewall. DC ground is about a 10" wire bolted to a seat bracket. I did recently install a DC noise filter on the power lead, as well as experimenting with a BCB AM LPF that I think is set around 1.8mhz. I forget the brand, but I originally intended it for the house setup since I'm right between to AM transmitter sites. My superbly tuned frequency-spectrum-noise-hunting-noise-canceling ears are telling me there is a wide range improvement on the entire HF spectrum, but there is a pronounced increase in hash starting right at 10mhz and up. it makes that portion pretty much unusable when the vehicle is running.

The vehicle is a 2003 Dodge Ram 2500 with a 5.9 Cummins. The noise is present when the vehicle is running. The noise dramatically drops off with the antenna disconnected, though I need to repeat this test and check around a few spots on the band to confirm if there is still noise in the receive with nothing attached on the antenna port. I believe the truck is set up to cycle the grid heater at start up, as right when I fire it up, there is a cycling of increased RF noise that coincides with a dimming of the lights, like a heavy load is cycling on and off with the warmer weather is only does this for a few moments then stops.

This the first time for me narrowing down and dealing with an "external" noise problem that is very specifically above 10mhz.

Thoughts? Ideas? Critiques?

 

[Fixitt]

As a retired auto mechanic, I’m thinking perhaps a bad diode in the alternator.

To test this theory, you could either remove the drive belt, or disconnect the alternator wiring and start the engine.

 

[mmckenna]

I know this isn't any help, but:

The vehicle is a 2003 Dodge

is not surprising. If you dig back through old posts on this site, you'll see a lot of RFI complaints from Dodge owners.

Might be the alternator, but I'd expect you to be hearing the noise coming through the DC power feed even with the antenna removed. Sounds like radiated noise from something.

Where/how is the antenna mounted? Is the radio chassis grounded, or are you just relying on the negative power lead (yes, I know they are bonded in the radio, or should be). Any external antenna tuners, etc?

 

[slowmover]

I’ve a 2004 CTD. Manual trans 2WD.

Don’t have the noise as described (the trucks are as close to identical as can be). The grid heater on mine hasn’t engaged during start-up for me to compare that.

Center roof mount antenna using a President Lincoln II on 11M. Power from batt.

I’m in an electrically noisy location, so the external sources haven’t been hard to ID.

With or without various filters tried or DSP speaker (ongoing install; the big truck has priority) I’ve been satisfied at lack of truck noise. Not dead silent, but “quiet”.

About (19) RF Bonds installed and all DC grounds upgraded (some new installed).

Gasoline versions of these trucks are another story.

 

[hanlonmi06]

lol...it's definitely a good 'ole truck...and I am prepared to accept that its just too RF unfriendly, but I gotta' give it a try. I'll run some searches for those posts.

The alternator was replaced in June of 2022. Radio is remote mounted under the seat with a home brew remote head cable, which leads me to the wonderful reason for posting- radio and remote cable are NOT bonded....so obvious to me now that the question's been asked. I used a shielded cable an totally forgot to utilize the shield.

Antenna base is essentially mounted to the inside edge of the bed rail. I added a strap to make sure there was a solid bond for the antenna "shield" to the bed sheet metal. There are also 2 straps added to the hood to the firewall cowling, one on each side. So today I am going to repeat the vehicle running and confirm whether noise is present and if so what intensity changes occur, at different spots in the band with the antenna pulled, then start in on some more bonding.

Question/observation: the noise is definitely there with it running, but its constant. it doesn't vary with engine RPM and right off the top of my head the one thing that runs but doesn't change its speed is the lift pump for the fuel system, which is mounted right at the engine, there is no pump in the fuel tank. If one were inclined to splice in some noise caps, what's a good value/type of cap to try and graft on to the power leads?

As an aside, I can always tune the antenna in to at worst a 1.5:1 and so far have been able to make some contacts on 40/20/10m so its functioning well enough in that regard.

 

[Fixitt]

The alternator was replaced in June 2022.

I have been a professional journeyman mechanic for over 40 years and have learned that new means Never Ever Worked. And just because it has been replaced does not remove it from the suspect list.
My line of expertise required that I not assume anything and test everything.
As a simple test, put a scope across the battery terminals with the truck running. You are looking for AC voltage. Not much, but if the rectifier/diodes are working, there should be no AC voltage. If you don’t see AC, another possibility is the electric fuel pump. If you put the scope on the fuel pump wires, you should see square waves with nothing else.

Since the noise is only there with the engine running, there can’t be much else.

 

[slowmover]

lol...it's definitely a good 'ole truck...and I am prepared to accept that its just too RF unfriendly, but I gotta' give it a try. I'll run some searches for those posts.

The alternator was replaced in June of 2022. Radio is remote mounted under the seat with a home brew remote head cable, which leads me to the wonderful reason for posting- radio and remote cable are NOT bonded....so obvious to me now that the question's been asked. I used a shielded cable an totally forgot to utilize the shield.

Antenna base is essentially mounted to the inside edge of the bed rail. I added a strap to make sure there was a solid bond for the antenna "shield" to the bed sheet metal. There are also 2 straps added to the hood to the firewall cowling, one on each side. So today I am going to repeat the vehicle running and confirm whether noise is present and if so what intensity changes occur, at different spots in the band with the antenna pulled, then start in on some more bonding.

Question/observation: the noise is definitely there with it running, but its constant. it doesn't vary with engine RPM and right off the top of my head the one thing that runs but doesn't change its speed is the lift pump for the fuel system, which is mounted right at the engine, there is no pump in the fuel tank. If one were inclined to splice in some noise caps, what's a good value/type of cap to try and graft on to the power leads?

As an aside, I can always tune the antenna in to at worst a 1.5:1 and so far have been able to make some contacts on 40/20/10m so its functioning well enough in that regard.

Bed to frame all four corners
Cab to frame all four corners
Cab to bed
Door hinges
Exhaust system.

Horizontal metal emphasized over vertical in priority.

RFI Problems

Bonding

Make up a bunch and have at it.



FWIW, in the big truck there’s noise that’s not going to be eliminated, but — as with DSP — cutting away the underbrush makes all else easier in RX-associated.

CB noise help

I noticed today, that when I turn my truck off, keys out, and after a minute or so when the accessory power goes off, my radio static gets much quieter. Also my signal improves. Someone, who before when they are at a certain location I could barely hear, but when this happens I hear them clear...

forums.radioreference.com

If the CTD primary system is still original, then an item from my list of near-future upgrades ought to be considered:

Gen 3 Dodge Diesel Truck Battery Cable Kits - CE Auto Electric Supply - Automotive Electrical Solutions

Order by 3PM AZ time M-F and by 1PM AZ time on Saturday and your kit typically ships the very same day! These kits fit 2003- 2009 Gen 3 Dodge Trucks with the various 5.9L or 6.7L Cummins Turbo Diesel Engines. These trucks originally came with dual batteries. We offer kits specific to the...

ceautoelectricsupply.com

This kit plus an upgraded alternator:

Mechman 2003-2005 Dodge Truck 5.9L Cummins Turbo Diesel Alternator - CE Auto Electric Supply - Automotive Electrical Solutions

This 240A unit fits the 2003-2005 Gen 3 Dodge Diesel Trucks with the 5.9L Cummins Turbo Diesel engines. 240A Units make 240A at Cruise and 170A at Idle! Offered in a Natural finish. We also offer a Big 3 Upgrade Kit for this alternator HERE. Full Specifications provided below. Includes a...

ceautoelectricsupply.com

You’ll find reviews, write-ups of installations and more on these and similar offerings on Dodge diesel truck forums.

Banishing age-related corrosion and increasing amperage at idle both seem a good idea for mobile radio, not just bolstering an only fair OEM system.

These are pickups designed for work. A trailer, A/C on, in rainy weather (headlights), 4-ways engaged, etc, is asking a lot in keeping DK voltage drop to 1/2-volt parked on the side of the road.

Also related is replacement of all drivetrain sensors, as age degrades performance. OEM still works, but . . . .

.

 

[popnokick]

Going back to the simple stuff, but am assuming these were all checked -
- USB-powered or charging devices usually plugged into 12VDC outlet, but may be wired directly
- Dashboard video camera
- Light bar on vehicle
All of the above have been reported many times here on RR as major generators of RFI / EMI.

 

[slowmover]

Common Mode Noise Filter - AC or DC Power - Wall Wart RFI Noise Filter - Palomar Engineers®

Some solutions here I’ve used. The David Navone RFI-N25 filter has a good rep in CB and car stereo circles. (Glad to see it’s carried here).

The DCCF-3 literally cured the compressor noise from a portable refrigerator/freezer I own.

More options from RF Parts:

Noise - Filters


.

 

[hanlonmi06]

When you go looking for problems, guaranteed you'll find them...imagine my surprise when I pulled the antenna connector out of the radio and the radio shut off. So I started there, lol. Loose connection on the DC plug was corrected so that I could repeat the antenna connected/not connected "data collection".

On the Alinco, you can use one of the knobs as a "vfo" in a course mode I used that to "sweep" up and down the HF band. The Tarheel is remote tunable so it was a compromise of trying to zip up and down with the antenna connected and not connected to compare against whether the antenna was resonate at a given frequency or not. Basically, there are two noises I am dealing with. There is an alternator whine that I hadn't really payed attention to but now that I am looking, I am finding, the problems. And there is the original hash that started this whole endeavor. With the antenna connected, truck running, its from S5 to S9+20 from about 9.900 to 16.500 mhz- the RX is washed out and unusable. With the antenna disconnected its audible but not hitting the S meter from 13-15.5mhz. The real problem is the hash, as it wipes out the receive. The alternator whine is audible but doesn't kill the RX even with the antenna connected. I'm calling it alternator noise for now because it does vary with engine RPM. Could be injectors...not sure what else is "electrical" that follows engine speed on this platform.

I put a scope on both batteries for the sake of checking both and could not see any AC on the scope. I have to get the wiring diagrams out to track down fuel pump wiring and where its easiest to tap in for scoping, but so far alternator appears to be working properly but its not off the list.

I affixed ground straps to the radio chassis and to the shield of the remote head cable at the end by the radio unit. All of the DC negative and braided ground straps all connect back to the same bolt I installed on the seat bracket if it matters. The DC power does have a noise filter installed in line at the radio. its an old Archer/Radio shack 20 Amp little box with the input side, output side and a ground connection. I think I am going to get the wiring diagrams out and start tracking down fuel pump wiring and start in on that and go from there.

I have incandescent after market off road lights. No LED.
The usb converter was the first thing I ripped out and tossed into the trash when I started all this.
The other DC to DC converter in use does not appear to be causing problems that I can tell. No changes to noise with that disconnected.
No cameras on board.
Prior to all the radio gear going in, I had checked and cleaned all grounds on the engine bay as I was dealing with practically every single dashboard idiot light being lit when I first inherited the truck from family from Texas.

Slowmover: I making my way through all the links, I like a few things I saw in them, thank you. It has definitely been used as an HD truck. 320k miles as it made many runs from Denton Texas to Northern Michigan hauling equipment. This is all a labor of love and madness, lol.

My experience has been hash would wipe out the entire band. Here, its definitely within a certain section of the band. Any thoughts about that as a clue to something on board to be considering like computer hash being "narrow'ish" like that?

 

[slowmover]

I’m an 11M guy, so other service frequencies don’t get any notable reading from me (at that point I’m going for general purpose knowledge).

Trailer light wiring boxes. Truck tuners. HVAC controls.

MORE DC grounds than OEM, and plenty of RF Bonds is what I’ve done.

I ran a tri-mag antenna mount on roof for years. Did the below last summer, and more quiet given what wasn’t bad before.



I’m not familiar with the FSM procedures on injector testing where one disconnects them singly to find the bad ones. But I’d try that approach given your dilemma (disconnect stuff ONLY via exact factory procedure).

Tread carefully if you go that route. Miles are one thing for deterioration, age is worse.

k0bg my guru as I could read and re-read (still do). See link on diesel pickups from W8JI in those pages (Ford).

The other sites where I read are WWDX and QRZ.

I haven’t found Dodge pickup forums to have the same depth on radio as Ford & Chevy pickup forums (time on their hands with truck in shop while we keep getting down the road), so I’d try those as well (radio, brand, service cross-reference searches).

Keep refining search here at RR. The install forum on which you’ve posted has as much or more info than I’ve seen elsewhere. (I also search posts by individuals; some I read their posts almost in entirety; ideas have popped up that way over many years, many forums on many subjects).

FWIW, I’ve found online videos to be short on depth. As a demonstration to text elsewhere are the better ones. (Keep at it, don’t get discouraged if info is low-grade or already familiar).

No other individual can touch Mr Applegate for his thorough approach.

.

 

[slowmover]

Reference kinda stuff

TRNW Store: A618 / 47RE RFI Noise Filters

HF RF Noise mobile Powerstroke Diesel Ford

Post in thread '2017 Ram 2500 Radio Installation Noise'

Post in thread 'RADIO NOISE? High pitch whine!!!'

Alternator AC volts

 

[AK9R]

Reference kinda stuff

The two links starting with "Post in thread" are not valid hyperlinks.

 

[slowmover]

2017 Ram 2500 Radio Installation Noise

Recently installed a Motorola PM 400 radio in my 2017 Ram 2500. Everything seems to work fine but am getting noise interference when the engine is running. I have handhelds as well and interference comes over them as well. Wondering if anyone has any idea what could be causing this. Thanks!!

forums.radioreference.com

RADIO NOISE? High pitch whine!!!

Ok so I’m a Diesel Technician, not a radio technician I’m working on it..... My truck, a 07 Dodge Ram 2500 with a Cummins Diesel engine has a high pitched whine noise with all radios ( narrowed it down to the truck Wife’s truck don’t do it ). High pitched whine when I start the truck, worse...

www.worldwidedx.com

 

[hanlonmi06]

Slowly parsing through everything...If I can make time this weekend I plan to start with bonding body/chassis points. I could have sworn things got worse/better when I had the hood open/close while scoping the batteries. I'm telling ya, my highly-precise-tuned-EMI-RFI-sensing probes attached to my skull..I should patent and sell these things!

Seriously though I intend to see this through as reasonable as possible. If I can locate the source/sources then the solutions become easy. in spinning the dial these last few days it does seem like there's been improvements. The hash was pretty much 10mhz and up before, but now the upper bands are somewhat usable again after a few things implemented. tbc...

 

[hanlonmi06]

I hate to be the type that posts, gets great responses then never follows up, so just want to acknowledge that. April in Michigan was not conducive to puttering outdoors on a hobby...

Anyhow, last night I had time and decided to try the coax cable for power lead trick. I had a scrap of old radio shack RG8 coax that seemed like a good candidate, so that went in last night. I left the DC power noise filter in line, but essentially ran from the battery, to the DC noise filter which is sitting right next to the radio with very interesting results. The "hash" is very much reduced. The RF noise floor is definitely a whole lot better in the few frequencies that I checked. This mornings drive into work I was able to listen to RNZ on 11.725 the whole way in where before I simply could not copy anything, even the strongest of SWBC around 10-13mhz.

The "alternator whine" is much more prevalent in the audio of the radio, but as mentioned the RF noise floor "hash" is very noticeably changed for what seems to be the better. The hash wiped out reception, the whine is annoying but even weak stations can be copied well with it present. The whine is engine RPM dependent, so that's a nice clue. Trying to divide and conquer this problem. Couple quick questions:

I connected the shield to the negative battery terminal. Is there a difference, RF wise, between a chassis connection and the negative battery terminal? I only connected one end of the shielding, should both ends of the shielding be bonded to the chassis?

I have been given the impression that grounding one end of shielding is a best practice from my industrial electrical experience, but I honestly don't think I ever researched this much myself, and I have seen both where one end is connected, or both ends are connected. And one last note, the truck is dual battery. All of the power connections I have made are on the drivers side battery and all leads pass pretty close to the ABS brain that's connected to the hydraulic unit. The passenger side battery is very close to the FCM, or front control module...dunno what the lesser of two evils is there, but the whole truck may as well be a hash box for all intents and purposes.

 

[mmckenna]

I connected the shield to the negative battery terminal. Is there a difference, RF wise, between a chassis connection and the negative battery terminal? I only connected one end of the shielding, should both ends of the shielding be bonded to the chassis?

On older vehicles, it's probably fine. On newer vehicles, they usually don't like things connected directly to the negative terminal since it can allow current flow to bypass the sensor that watches vehicle power use. 2003 pickup is probably well before that was implemented.

On an older GM truck, I had a dual band mobile installed. I landed the negative at the battery terminal and had substantial alternator whine on transmit audio.
I moved the negative lead off the battery to a chassis ground and it resolved the noise.

In the commercial world, grounding directly to the vehicle chassis close to the radio is the preferred method.

I have been given the impression that grounding one end of shielding is a best practice from my industrial electrical experience, but I honestly don't think I ever researched this much myself, and I have seen both where one end is connected, or both ends are connected. And one last note, the truck is dual battery. All of the power connections I have made are on the drivers side battery and all leads pass pretty close to the ABS brain that's connected to the hydraulic unit. The passenger side battery is very close to the FCM, or front control module...dunno what the lesser of two evils is there, but the whole truck may as well be a hash box for all intents and purposes.

You are on the right track. The concern would be current flowing through the shield, as in a ground loop. In a vehicle where everything should be properly grounded, that shouldn't be an issue. You could try it both ways and see if there is a difference.

As I mentioned above, running the radio negative lead direct to chassis ground can be a better method. Keeping that ground short helps reduce chances of it acting like an antenna. Let the vehicle chassis do it's job.

You should only need a positive off the battery to the radio. Running that away from the ABS module and the rest of the noisy electronics might solve some more of the issue. You could run off the other battery if that made this easier.

 

[hanlonmi06]

The easiest run to install was the option near the ABS unit. Both batteries sit next to computer module of some sort so it boiled down to the one that took less wire. To clarify, I am not using the shielding as a power connection. The radios negative power lead is connected to nearby chassis, and I did make use of the radios chassis ground screw with a braided strap to nearby chassis as well. My goal with the coax trick was to see if shielding the power lead made any difference- seems like it did! I was going to experiment with bonding both ends as something to try.

I'm pretty sure this truck pre-dates the current sensing on the negative side, as there are more than one factory installed negative terminal connection to ground points under the hood...so, many wires on the negative terminals of both batteries. I'm just excited that something made a substantial difference. I live on a dirt road and its been pretty rainy, so I have been dragging my feet on getting straps installed on the bed, exhaust, ect. We are due for some nicer weather, so that's likely a next big step.

 

[mmckenna]

The easiest run to install was the option near the ABS unit. Both batteries sit next to computer module of some sort so it boiled down to the one that took less wire. To clarify, I am not using the shielding as a power connection. The radios negative power lead is connected to nearby chassis, and I did make use of the radios chassis ground screw with a braided strap to nearby chassis as well. My goal with the coax trick was to see if shielding the power lead made any difference- seems like it did! I was going to experiment with bonding both ends as something to try.

OK, got it. My Ford has one battery on either side, so running down either side of the engine compartment is possible.

I've done the same thing on a few vehicles, even though the negative power lead is grounded to the chassis near the radio, and the negative lead is grounded to the radio chassis, I've put in a short ground strap from radio chassis to the vehicle chassis.

I've seen hams using the coaxial power trick. I've seen some run two separate runs of RG-8, one for positive, one for negative, both shields bonded to the chassis.
I've never seen that necessary on a commercial install, however. That is usually because effort is made to route the power feeds away from noise sources, and they are VHF/UHF/7-800MHz, which is a bit less troubled by vehicle electronics.

I think the best approach is to experiment, which you are doing. That's part of the hobby, and it certainly seems like you are making some good headway.

I'm pretty sure this truck pre-dates the current sensing on the negative side, as there are more than one factory installed negative terminal connection to ground points under the hood...so, many wires on the negative terminals of both batteries. I'm just excited that something made a substantial difference. I live on a dirt road and its been pretty rainy, so I have been dragging my feet on getting straps installed on the bed, exhaust, ect. We are due for some nicer weather, so that's likely a next big step.

I think it does, too. I believe the power management stuff started to show up in the 20-teens.

Good luck and keep us up to date. What you learn will benefit others.

 

[AK9R]

I'm pretty sure this truck pre-dates the current sensing on the negative side, as there are more than one factory installed negative terminal connection to ground points under the hood.

My 2011 F-150 had current sensors in the ground wires going to the battery's negative terminal. The current sensors were wired to the ECU. That was the first vehicle I saw with any kind of battery management system. As I recall, there were three wires going to the negative terminal.