VHF interference from 12v compressor fridge

MattS

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As yet another feature of some ongoing boat fridge sagas, I've now discovered that when running the control unit / compressor radiate RFI (on Ch74 specifically it seems, which is frustratingly my local VTS station so my normal channel to listen to...). I'm pretty sure it's radiated rather than electrical connection, as it affects my two handheld units as well, even when out in the cockpit.

I have just installed a replacement control unit (a cheap compatible unit from Ebay) - so I'm half suspicious that is the cause.

Googling has revealed quite a few previous reports of this, but no solutions that I can see. The best seems to be "don't use the fridge whilst you're using the radio" which isn't going to be that practical really.

I don't suppose anyone has actually found a way to address RFI from 12v fridges?
 

William_H

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And use suppression ferrites in the supplies to the Vhf
No he thinks it is radiated from the controller. Suppressors ferrite and capacitors on the supply to the fridge would be more appropriate.
U15 Ferrite Voltage Spike Protectors/Noise Suppressors - Pk.2 | Jaycar Electronics
100uF 50V Bipolar Electrolytic Capacitor | Jaycar Electronics
220nF 50VDC Ceramic Capacitor | Jaycar Electronics
A filter would have the ferrite on the supply cable near the controller. Us both one after the other. The 2 capacitors would connect positive to negative supply on the controller side of the ferrite and as close as possible to the controller. The large value capacitor will act a bit like a battery to smooth out the pulses of current flow but might not catch the very high frequency interference. The small ceramic capacitor with short lead connections will handle very high frequency pulses. (interference). A grounded steel box or faraday cage would be the next step if filter does not fix problem. ol'will
 

Neeves

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If you think the issue is produced by a cheap control unit of eBay then the obvious, and maybe cheaper and safe solution is to buy the genuine control unit. If the problem persists you then have a reputable company to whom you can make complaint.

If there are reports of this issue with these units........??

Just out of interest how much are the genuine and eBay units? Which fridge?

Jonathan
 

MattS

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I have zero knowledge about such things, but my immediate reaction was to suggestion building a Faraday Cage around the control unit.

I did think about this, but the control unit gives off a fair bit of heat, so I'm quite nervous about enclosing it in anything that restricts air flow. I did try a bit of tin foil around it to see if it would make any difference but didn't manage to get much effect.

If there are reports of this issue with these units........??

Just out of interest how much are the genuine and eBay units? Which fridge?

The reports don't seem to be specific to the cheaper Ebay ones - they seem to be general complaints relating to 12V compressor fridges. I have to admit I haven't actually found an 'official part' as such, only control units that Penguin sell for the BD35F compressor which are £234 vs £99 (at which point you almost may as well spend £550 to update the whole compressor setup...).
 

MattS

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No he thinks it is radiated from the controller. Suppressors ferrite and capacitors on the supply to the fridge would be more appropriate.
U15 Ferrite Voltage Spike Protectors/Noise Suppressors - Pk.2 | Jaycar Electronics
100uF 50V Bipolar Electrolytic Capacitor | Jaycar Electronics
220nF 50VDC Ceramic Capacitor | Jaycar Electronics
A filter would have the ferrite on the supply cable near the controller. Us both one after the other. The 2 capacitors would connect positive to negative supply on the controller side of the ferrite and as close as possible to the controller. The large value capacitor will act a bit like a battery to smooth out the pulses of current flow but might not catch the very high frequency interference. The small ceramic capacitor with short lead connections will handle very high frequency pulses. (interference). A grounded steel box or faraday cage would be the next step if filter does not fix problem. ol'will

Thanks - I can definitely try putting a ferrite on the supply cable.

Would the 2 capacitors need putting onto the circuit board inside the controller itself?
 

GHA

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I did think about this, but the control unit gives off a fair bit of heat, so I'm quite nervous about enclosing it in anything that restricts air flow. I did try a bit of tin foil around it to see if it would make any difference but didn't manage to get much effect.
VHF never had problems ( known about anyway..) but MF forget it, just turn it off if you want a weatherfax, just too noisy. Danfoss do a metal case for the noisy controller (got one) but it doesn't do much.

A few tips here >
Eliminating Radio Interference from Fridge Compressors - Practical Sailor
 

MattS

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Interestingly, Penguin have replied to me and said that the metal casing on my original duff unit was actually there to prevent VHF interference.

B55C247B-7D33-4A8A-BA1F-CA3A71AF6467.jpeg

The new unit I bought from EBay doesn’t have any kind of shielding around it, but based on the pictures on the Penguin website neither does the unit Penguin sell for £234 - I’ve asked how their unit avoids the interference! It may be the reason for the price difference (£99 vs £234)

DANFOSS BD35F/BD50 CONTROLLER 12/24V
 

William_H

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Thanks - I can definitely try putting a ferrite on the supply cable.

Would the 2 capacitors need putting onto the circuit board inside the controller itself?
Yes ideally if you can open up the controller and add to the circuit board if not the big one then at least the small ceramic C. Or just mount outside with conenctions as short as possible to +ve and -Ve. ol'will
 
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