The Waeco fridge's compressor interferes with the AM radio. I like to listen to ABC (a smaller BBC)! It is ok in the city where there is a strong signal, but in the outback, the weaker the signal the more difficult it is to hear the radio. Obviously Murphy gets involved & bug_ers up the sound whenever there is something interesting. The compressor's timing is impeccable!

I have mostly used sarking tape & a bit of heavier aluminium tape. To get the tape into the tight spots I double back some backing paper. In the really difficult areas where it was hard to pull the tail of the backing paper off I made 3 sections. This works really well. (save large pieces of backing paper)

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Have you fitted (high frequency) suppressors to any wires leaving your cabinet. As well as disturbing other power supplies, they will act as aerials re-transmitting the electrical noise. FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 77k+ miles) (MY2015)
Metro in its 11th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)

Isn't what this is for. I get the same interference whether only AC or only DC is physically connected. This is on the AC line.

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Does the fridge have a fan? In my (limited) experience variable speed fans have a higher impact on AM interference than compressors.

It is the compressor because it starts at a slightly different time to the fan & the noise on the radio is in time with the compressor spooling up or down.

I have had 3 different fans in there to improve efficiency. The last 2 being Noctua fans. I also use one of these fans in the car as a home made desktop fan & had no issues. It is the same as the previous fan in the fridge.

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If your stand alone radio works perfectly alright and your car radio doesn't, then, I feel that you need to suppress All power wiring from fridge, and make sure that everything is properly earthed to car. (you seem to have proved it's not RF radiation interference)

Can you experiment by running fridge and radio on completely separate supplies?

You could also check aerial by substituting it for a long bit of wire.

See below for tips, there is quite a lot about it if you search AM Radio Interference on Web.

https://www.lifewire.com/curing-car-audio-static-534627 FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 77k+ miles) (MY2015)
Metro in its 11th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)

It happens to the car radio & to 2 different portable radios which both of these run off there own AA batteries. We listen to AM in the car at night when camping using a portable radio not to flatten the car battery & the car also switches off after 10 minutes anyway.

The fridge runs off its own battery not connected to the car, often forgetting to manually plug in (until recently adding DC-DC) the fridge's battery to charge it up.

It is only AM that is an issue & the problem seems to be fixed.

The same noise occurs when the fridge is in the house running off 240v or on a 12v battery. I test the fridge using a spare 12v battery. Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

Sorry, on first reading your post, I thought you were reporting a problem and asking for help.

I see now that you were reporting modifications which you believe overcame your problem. FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 77k+ miles) (MY2015)
Metro in its 11th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)