FM Radio Interferance Whilst Charging Phone

[BargeeSpud]

Hiya,

 

I don't often charge my phone whilst the radio is on as I tend to only listen to the radio first thing & I charge my phone during the day or evening. However, I have noticed that when I charge my phone with the boat's radio tuned in to an FM station, I get a constant hissing type of interferance at the same time which goes if I unplug the phone.

 

What is the best way to eliminate the problem? I'm considering fitting a ferrite sleeve on the phone's charger cable, but maybe there's a better way to suppress the interferance & if so, I'd like to know what it is.

 

Cheers.

[pete.i]

Phone chargers are pretty basic even the wildly overpriced Apple ones. They wont give a nice clean sine wave output. Usually the best you get is a slightly modified square wave. Square waves are made up of all the frequencies in the band so poor phone chargers will interfere with radios especially if the radio and the charger are in close proximity to each other. The real cure is to use a much better charger to charge your phone but as phone chargers are specific to the phone they came with that isn't possible. I suppose using a ferrite bead or beads on the charger lead might work but to be honest I would think it's a "suck it and see" thing. There are some battery chargers, ie they use a battery to charge the phone rather than down rated mains voltage but I suppose the batteries wouldn't last very long and they are like an emergency standby thing. I think the easiest thing to do is try and move the charger and phone as far away from the radio as you can although some interference can be transmitted via the mains wire. The other solution may be to try a car charger. These work off the 12 volt system so shouldn't produce interfernce but even so the battery ones still have to reduce the voltage and that is done with a switched mode type supply and that will produce interference. One other solution might be to get a DAB radio. I haven't had a lot of success with DAB on my boat as DAB does seem to want a much stronger signal that FM.

[Chalky]

If your FM radio runs off the boats power supply then you may have conducted interference that's getting in through the wiring or radiated interference. If it runs off batteries and isn't connected to the supply then its radiated interference. Radio frequency interference is a black art - what will work in one situation doesn't always work else where.

 

Firstly make sure that all power connections (especially gnd / 0V) are in good order. If you use an external aerial check the connections are clean and in good condition. If aerial is powered check its working.

 

If it's radiated interference then try separating the charger and radio as far apart as you can (the interference will decrease as the distance increases).

Also try to put the radio and its arial as close to a window as you can (you should get a better signal and noise will be less of a problem).

If none of the above work try moving the radio to different places (the radio waves will bounce round the boat and in some places you'll get a better signal, some worse).

Another approach may be to look for the same station on a different frequency (or a different station all together). If the noise is narrow band (single or very few frequencies) then this may get you round it. If its broad band noise then you're a bit limited.

 

If its conducted interference then try running the radio off batteries or connect to a power supply that's connected to a different fuse in the main panel. Also significantly increasing the size of the 0V cable can help - the filters in the charger and radio conduct noise to 0v. If the cable's too small the filters don't have the required effect. If its conducted then ferrites on the leads may help.

[BargeeSpud]

Sorry, insufficent detail given - again! The radio is a standard car radio run off the boat's 12v & I have a BlueSea USB charger socket. I use a USB/microUSB cable to connect the phone.

Edited April 26, 2015 by BargeeSpud

[pete.i]

Even so Spud that charger socket still drops the voltage fron 12 volts to the 5 volts that a USB socket runs at. However it does that will introduce interference. Your still looking at ferrite beads or a ferrite toroid on the supply lead but I don't think that will work still the best solution is to get the 2 devices as far apart as you can. Can you run the radio off separate internal batteries as per a domestic radio or is the radiol a car type one?

Edited April 26, 2015 by pete.i

[Keeping Up]

It's like when I used to repair TVs for a living, we used to reckon the best cure for interference on the picture was to wrap the user in tin foil.

[Tony Brooks]

With the 12V phone chargers I find moving it to another socket on a different circuit usually works. With the 12V computer supply it does it whichever socket we use. All socket within a metre or two of each other. No interference when charging at the other end of the boat.

[DHutch]

We have a 12v car charger, and a car radio, both working off the same stepdown 24v to 12v unit and had no issues.

 

However, charging the batteries from the mains, does induce noise on the radio.

 

 

 

 

Daniel

[Neil TNC]

I had a similar thing when I was fitting out barge Maurice A. I got to the stage when I was wiring up / testing the low level led lighting, with the Victron plugged into the mains. About this time we noticed a lot of interference on the workshop radio. This was cured by replacing the cheap led modules, as the regulators were chucking out and immense amount of radio frequency interference!

[John Williamson 1955]

For a 12 volt charger, try a ferrite ring round the USB lead with the cable passed through it twice. The best result may be with it at the charger end or the phone end, depending on whether it's power supply or the phone generating the interference. Alternatively, if it's a car radio, then making sure the aerial lead has a good connection to earth, and preferably has an earthed metal plate between it and the charger may help. Failing all else, and if it's a portable radio, doubling the distance between the charger and the radio will result in a quarter of the interference.

 

As has been said, chasing and eliminating interference is often something where a knowledge of the Dark Arts comes in handy.

Edited April 28, 2015 by John Williamson 1955

[Chewbacka]

The older chargers were simple transistor volt droppers, so the unwanted voltage (12 down to 5) was lost as heat. The tiny little adapters that plug in flush to the 12v socket are little switch mode supplies - small, efficient but chuck out a lot of rf noise both through the air but also back into the supply wiring. Different circuits and distance is best, but other than that get an old style charger, or don't do both at the same time.

[Ian Mac]

Could well be the phone as some of them use current pumps to get the charge into the batteries. Different phones do it different ways. Ferrite beads on the USB cable and tin foil around the phone, are always a good starting place, as already suggested. It also depend on if its interference which is being transmitted directly via radio waves or is it travelling at lowewr frequencies over the "mains" cable system. TVI is always a black art! In theory all electronics have to pass a basic TVI tests however the slightest mod knackers this, charging leads are now notorious for this, especially the more powerful ones.