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Old 30-01-2014, 01:15   #1
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Rf interference on vhf/ssb from fridge.

I have a danfoss compressor system that is causing bad intererence on both my VHF and SSB when it is running.

Does anyone know of a possible solution? At the moment I turn off the fridge when using radios, but then I forget to turn on again, causing my beer to go warm, obviously not an acceptable situation!!

I was advised to put a capacitor between +ve and -ve wires at compressor? Easier said than done on my boat due to location of compressor, so before I jump in, any other solutions?

Thanks in advance

Charlie.
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Old 30-01-2014, 01:24   #2
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Re: Rf interference on vhf/ssb from fridge.

I don't believe there is any fix for the interference other than turning off the fridge. The typical Danfoss compressor contains a little 3" x 5" black box mounted on the side of the compressor. Inside that box is a DC to AC inverter since the compressor actually runs on AC not DC power. That is the source of the RF noise.
I can only suggest that you make a little sign that you place/stick on the fridge reminding you to turn it back on again.
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Old 30-01-2014, 01:38   #3
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Re: Rf interference on vhf/ssb from fridge.

Not sure I agree with that. There are two possible entry points for the noise to get on the VHF. One is the power supply, one is RF noise received through the antenna. The first is the easiest. Are they on the same battery? If you change the supply for the VHF (temp is OK, just testing) to a dedicated battery, is the noise still there? If so it's RF noise, if not its on the power side. Come back here with the results and we can continue...
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Old 30-01-2014, 03:28   #4
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Re: Rf interference on vhf/ssb from fridge.

Sadly this is a well documented RFI issue, and to the best of my knowledge, one that has yet to be solved. It is RF generated by the switching power supply, and it radiates very well indeed (not coupled through the wiring). We have noted the characteristic bleeping from boats anchored hundreds of feet away from us... sort of DX RFI!

Interestingly, the older Danfoss systems do not exhibit this clever feature. I'm happy to say that our 21 year old Danfoss fridge does not cause RFI. Sure hope that it continues its already long life!

Cheers,

Jim
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Old 30-01-2014, 08:37   #5
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Re: Rf interference on vhf/ssb from fridge.

Quote:
Originally Posted by Neptune's Gear View Post
If you change the supply for the VHF (temp is OK, just testing) to a dedicated battery, is the noise still there? If so it's RF noise, ...
Tried that with the same compressor and RF noise still there, it's well known, they do a metal jacket to go over the inverter but it didn't help much either. But Vhf noise sounds like it might be something else, I have no problem with such high frequencies.
I have a little relay waiting to get fitted which will turn off the fridge when the ham radio is turned on. So far it's been postit notes
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Old 30-01-2014, 08:57   #6
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Re: Rf interference on vhf/ssb from fridge.

I have that problem with my Engle Refrigerator/Freezer, but no the Boat Adler Barbour. It also has a built in inverter.

The VHF is clear but I do get a whine on the SSB.

I have place magnates and chokes on power cords on both the freezer and the radio... No luck!
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Old 30-01-2014, 09:10   #7
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Re: Rf interference on vhf/ssb from fridge.

Another suggestion - try this - a T-4 Line Isolator from The RADIO WORKS
I put one into my SSB setup and there was a noticable decrease in noise.
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Old 30-01-2014, 14:50   #8
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Re: Rf interference on vhf/ssb from fridge.

Cover the DC-AC converter box in aluminium or carbon fiber, and thereby encapsulating it in a sort of faraday cage?

That won't help with other people's fridges interfering with your reception, though. I have never experienced this kind of thing, and I only own a VHF, no SSB.

Edit: Scratch that, I see they already suggested that to you.
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