ARB Refrigerator causing RFI on handhelds

[James86004]

Hi All,

We have an ARB fridge mounted between the front seats of our 04 Sprinter. I have not gotten around to installing a mobile radio in this vehicle yet, so we use handhelds, both Icoms and Baofengs. They both get a strong, annoying signal whenever the compressor is running. It happens on both 2 m and 70 cm. Is there a filter we can install to prevent this? Or do we need to move the refrigerator farther away?

The 25 year old Engel fridge we have in our Range Rover does not cause the same problems.

 

[Herbie]

You could try a choke on the power cable, but if the noise is radiating from the compressor motor itself, this won't help. Danfoss compressors are brushless, so noise filtering is more difficult than just adding a capacitor to the leads like one might do on a brushed DC motor.

 

[DaveInDenver]

Are the radios powered from the truck or on their own internal batteries? Or does it happen all the time regardless of power source?

 

[James86004]

Internal batteries.

I just installed a 2m mobile and external antenna, lets see if that fixes the problem.

 

[DaveInDenver]

With the HTs running on their own internal batteries then you're dealing with radiated inference from the fridge. Putting the antenna outside should help but also make sure all your coax and connectors are in good shape. You might still have interference but sheet metal and physical distance between the fridge and radio should help.

The alternative is conducted interference, which is what happens when two devices share a path such as your vehicle power system. The noise from one is conducted to the wiring of the other. This is harder to remove because it's like a direct injection of the offending interference into your radio.

 

[axlesandantennas]

Handhelds with the attached antennas are going to pick up a ton of RFI. Getting the antenna outside the vehicle should be your best bet.

 

[James86004]

So, before our Christmas trip, I decided to install our Kenwood TM-281A 2m radio along with an external antenna in the roof. The radio is about 3 feet from the fridge. There is still RFI, albeit a little less. It is till annoying.

Our 92 Range Rover with an early 90s Engel fridge does not have this problem.

 

[axlesandantennas]

So, before our Christmas trip, I decided to install our Kenwood TM-281A 2m radio along with an external antenna in the roof. The radio is about 3 feet from the fridge. There is still RFI, albeit a little less. It is till annoying.

Our 92 Range Rover with an early 90s Engel fridge does not have this problem.

I'm sure you checked, but is the noise only while the fridge is running? Or while the fridge and the vehicle is running?

It is difficult to get rid of RFI. I have a set of quadratec led aux lights that throw off a large amount of RFI. So bad I get it with local FM radio stations. BUZZZZZZZZZ!

You may just have to crank up your radio squelch. I had a TM-281 like yours. It's an awesome radio except that the lower power setting was 25 watts. I'd crank up the squelch to max and see if that helps. You will still be seeing your S-meter moving or pegged, but it may cut out the noise. Also, what coax are you running? For mobile installs, I don't use anything less than RG-8x. It may/maynot help, but it's worth a look.

 

[DaveInDenver]

Man, squelching out RFI like that is going to kill your range. If you have to use more than 50% range on the squelch you're limiting yourself to a few miles. A lot of people run fridges and radios without raising their noise floors appreciably so it's a solvable problem once you've identified the source and mode of interference.

This sure stinks of a grounding issue to me. It does it on radios powered both from the truck and independent of the truck. With a fixed HT antenna and with an external antenna. So the fridge has to be generating noise that's coupled to the body or truck harness such that it's radiating widely. I bet you hear it on an HT standing outside the truck a few feet away.

 

[axlesandantennas]

Man, squelching out RFI like that is going to kill your range.

I do agree with this 100%. But! I tend to go out with one or two people/ vehicles so I could set max squelch and not run into a problem. It is also, in the end, a band aid fix for the problem. I would track down the issue for sure, but if you get RFI on the trail and you are just using radios at no more than a few hundred yards, I'd crank the sq to max just to keep from going nuts.

 

[James86004]

Thanks for the insight, folks.

I'm sure you checked, but is the noise only while the fridge is running? Or while the fridge and the vehicle is running?

It is difficult to get rid of RFI. I have a set of quadratec led aux lights that throw off a large amount of RFI. So bad I get it with local FM radio stations. BUZZZZZZZZZ!

You may just have to crank up your radio squelch. I had a TM-281 like yours. It's an awesome radio except that the lower power setting was 25 watts. I'd crank up the squelch to max and see if that helps. You will still be seeing your S-meter moving or pegged, but it may cut out the noise. Also, what coax are you running? For mobile installs, I don't use anything less than RG-8x. It may/maynot help, but it's worth a look.

I am not sure if it is while the vehicle is running too, or not. We have not used the radio when we are stationary.

I used 9 feet of this coax: https://www.qsradio.com/shop-now.html#!/Bury-Flex%E2%84%A2-50-OHM-Very-Low-Loss-Coax-Jumper/p/51240435/category=13362076

This sure stinks of a grounding issue to me. It does it on radios powered both from the truck and independent of the truck. With a fixed HT antenna and with an external antenna. So the fridge has to be generating noise that's coupled to the body or truck harness such that it's radiating widely. I bet you hear it on an HT standing outside the truck a few feet away.

The fridge is grounded to a post under the front right seat, which is the same place Mercedes grounds their auxiliary battery. I needed a bigger battery that would fit, so I put two 6V golf cart batteries in series under the rear seat and ran power and ground cables from them to the factory connections under the front seat.

 

[DaveInDenver]

Nothing wrong with that Bury-Flex. The concern would be the quality of the connectors and you bought it made up so that's probably not a problem.

Davis RF Co. - Bury-FLEX Flexible Low-Loss Coax

www.davisrf.com

 

[DaveInDenver]

The fridge is grounded to a post under the front right seat, which is the same place Mercedes grounds their auxiliary battery. I needed a bigger battery that would fit, so I put two 6V golf cart batteries in series under the rear seat and ran power and ground cables from them to the factory connections under the front seat.

It's not a simple task tracking down interference but suffice to say RF is not like DC. So what works for a remote battery doesn't means it's good for electrical noise. It can be maddening. Generally speaking you want short grounds that are clean and solidly connected, which it sounds like you have. In extreme cases power has to be treated like RF using shielded and impedance controlled cables. It should be necessary but never know. Also shielding goes a long way. IOW conductive foil or light gauge sheet metal or mesh to construct literally boxes (fancy named Faraday cages) around things.

 

[axlesandantennas]

Thanks for the insight, folks.

I am not sure if it is while the vehicle is running too, or not. We have not used the radio when we are stationary.

I used 9 feet of this coax: https://www.qsradio.com/shop-now.html#!/Bury-Flex%E2%84%A2-50-OHM-Very-Low-Loss-Coax-Jumper/p/51240435/category=13362076

The fridge is grounded to a post under the front right seat, which is the same place Mercedes grounds their auxiliary battery. I needed a bigger battery that would fit, so I put two 6V golf cart batteries in series under the rear seat and ran power and ground cables from them to the factory connections under the front seat.

Roger that.
The first thing I would do is see if you can eliminate where the noise is coming from. Turn the vehicle on with engine running. Then only turn on the electrical portion. Then turn on only the fridge. Maybe too, if you can run a power cord to the fridge if it can run on AC just to see if you can eliminate the problem.

Just saw too that your old Engle does not cause this problem, so that really does narrow it down, but I would preform the above tests anyway.

Out of curiosity, which Icom HT are you using?

 

[James86004]

The HT is an Icom IC-T90A that I have had since I got my license in 2009.