Ford Chassis Ambulance VHF Interference

[charleswmoore]

Hey folks has anyone experienced Radio Interference in the VHF band being generated by a 2019 Ford Chassis Ambulance. This is actually a 2020 Osage ambulance. I have almost 8 db of receiver degradation once the ignition key is inserted. It also degrades other vehicles when closely oriented so antenna reloacation would not be a fix. Also effects handhelds when near the vehicle. I can see the noise floor on the spectrum rise significantly when ever the vehicle systems are woke up. Does not have to be started just woke up! Sniffing the vehicle it appears it is strongest when probing around the Dash display. Also I did a test in the UHF band and degradation is measurable but in significant to cause problems. If anyone has seen a product bulliten on anything I can hang my hat on would be great, Thanks

 

[k3hal]

fwiw...
i had a full size bronco w/same prob. ford had an issue they chose to push aside because there was no need to cater to us techies! try not to rule out the fuel pump that is located inside the gas tank. good luck.

 

[chief21]

Chassis-related possibilities include fuel pump and vehicle computer(s) and/or display(s). Since you mentioned that the strongest signal seems to be located at the dash, I'd concentrate on the vehicle computer/display as the most likely problem.
Body-related possibilities (if present) could be numerous... siren/PA system, strobe lighting, LED lighting, GPS, laptop/mobile data and mobile radio equipment - to name a few. If there is a master switch in the console, confirm that ALL of the accessory circuits are controlled by the master and check for anything that might still be powered up.

 

[a417]

I'd get Osage involved, as they're involved in upfitting.

BTW, 17 years is a long time for a first post, congrats!

 

[n3obl]

check to see where they tapped the power for the radio power leads. Seen a recent thread elsewhere about a ground going into the multiplex system. Hence no adequate ground.

 

[kayn1n32008]

check to see where they tapped the power for the radio power leads. Seen a recent thread elsewhere about a ground going into the multiplex system. Hence no adequate ground.

I was just thinking the exact same thing.

 

[n3obl]

and it was osage also. wonder if the factory is not running wiring properly ?

 

[kayn1n32008]

and it was osage also. wonder if the factory is not running wiring properly ?

Someone taking a shortcut?

 

[charleswmoore]

Hey folks has anyone experienced Radio Interference in the VHF band being generated by a 2019 Ford Chassis Ambulance. This is actually a 2020 Osage ambulance. I have almost 8 db of receiver degradation once the ignition key is inserted. It also degrades other vehicles when closely oriented so antenna reloacation would not be a fix. Also effects handhelds when near the vehicle. I can see the noise floor on the spectrum rise significantly when ever the vehicle systems are woke up. Does not have to be started just woke up! Sniffing the vehicle it appears it is strongest when probing around the Dash display. Also I did a test in the UHF band and degradation is measurable but in significant to cause problems. If anyone has seen a product bulliten on anything I can hang my hat on would be great, Thanks

Thanks for the replies: We are going to take a few steps and see if we can reduce the level to a livable amount????

1) Relocate Radio transceiver from behind passenger seat
and move it into Box area. This will give us more shielding
between Radio and Dashbrd dispaly.

2) Explore the relocation of primary dispatch antenna from
optimum location of center of the box to the far rear
of unit. Again this will give us more shielding from
dashboard to antenna.

3) Install additional bonding straps between hood brackets
and chassis. This is to possibly reduce the amount of signal
being radiated from wiring passing through fire wall.

 

[kayn1n32008]

Before doing any of that, ensure the radio is grounded to the chassis of the ambulance. Moving the RF deck away from the dash won’t likely help any, nor will moving the antenna.

 

[OhSixTJ]

Diesel engine? I have the same problem on my 2015 F250 6.7. Incredible noise when the systems are awake. I’ve tried grounding to the body AND the battery and nothing changes. These are NOISY vehicles.

 

[timkilbride]

I just had a similar issue in a mobile setup. The culprit was a USB charger plugged into the accessory outlet.

Tim

 

[mmckenna]

Diesel engine? I have the same problem on my 2015 F250 6.7. Incredible noise when the systems are awake. I’ve tried grounding to the body AND the battery and nothing changes. These are NOISY vehicles.

I have a 2018 F350 with the 6.7. A vhf analog radio, and no issues at all.

Like Tim said, I've had similar issues with noisy/cheap Usb adapters. In fact, one my son has for his Nintendo Switch will screw up the tire pressure monitoring system on my wife's car.

 

[charleswmoore]

I don't like to keep folks hanging, This is what we have done,
1) Moved radio from in cab to inside ambulance box to gain some separation from console.
2) Ran A+ power lead straight to battery.
3) Installed braided ground straps across hood hinges.
4) At random installed ferrite snap on Cores on wiring under dash feeding display.

While testing unit we found that without an antenna screwed on MOT mount and utilizing
a MOT to UHF female screw on adapter even direct connected the service monitor the vehicle
reduce radio rec fro .18 microvolt to .8 microvolts. sensitivity, Because of this we replaced the standard RG58
antenna cable with LMR400 cable between radio and MOT mount. This eliminated that concern. We also
moved antenna from forward half of ambulance to far rear trying to gain as much isolation as possible.
This reduced the measures interference by 7 Db. We still have a measured 12 db of interference which is huge!!!!
Yes we gained some range and it now performs the equivalent of a handheld which is still sad at best. There is no way
a local dealer can diagnose this, it will have to come from Ford engineering department and I am guessing this will take much time if ever resolved.

 

[a417]

Ahh, the infamous mobile LMR400 installation. God bless ya.

 

[OhSixTJ]

I have a 2018 F350 with the 6.7. A vhf analog radio, and no issues at all.

Like Tim said, I've had similar issues with noisy/cheap Usb adapters. In fact, one my son has for his Nintendo Switch will screw up the tire pressure monitoring system on my wife's car.

I don’t have any USB adapters but I did wire in some 12v outlets for the backseat passengers. Don’t think they’re the culprits though as they are on all the time and the noise only happens when the key is in the forward “on” position. The hunt continues....

 

[jamx316]

put key in, pull fuses one at a time until noise stops

 

[mmckenna]

Yeah, that's what I'd start doing.
Before you go to Ford with this, making sure all the stuff the upfitter did is removed from the equation. Something RFI related, so anything with a switching power supply, monitor, computer, etc. I'm sure you've looked at all that stuff already, but sometimes having a second set of eyes on it can help.

 

[Ubbe]

I have a radio amateur here that testifies that when his LED rear lights are lit it kills his 145MHz reception.
Both Xenon and LED lights are known to sometimes interfere with radioreceivers reception.

/Ubbe

 

[12dbsinad]

Like others have said, try to figure out the source and see if it's the aftermarket equipment. It may be more than one thing, so keep that in mind. Sweep the truck with a spectrum analyzer to narrow it down and start shutting things off. It could be anything that's microprocessor controlled, LED lighting, switching power supplies, etc.

Just for FYI, our shop just had a bunch of transit buses in for the same problem on VHF. Turned out to be the Multiplex control boards in the electrical panel. They would radiate junk up to about 350-400 meg, and with all the wiring going to it made it act like a big antenna system throughout the bus. The techs installed ferrit on just about everything which helped, but didn't totally get rid of it. Welcome to the new age of RF! Can't even put a VHF radio in a vehicle anymore and have it work! Good luck!