DAB radio electrical interference

[Starcoaster]

I have a little DAB radio that plays fine until I plug my laptop in to charge... then it totally breaks up and makes a very non-musical and annoying noise.

It only happens when the laptop is plugged in and in use, not when it is either in use on the battery or plugged in and turned off.

I have tried moving the laptop and the radio as far as possible from each other, as well as ensuring they are not connected to the same socket, but the distance I can get them from each other while still being able to use both is apparently not far enough to be effective.

Why does this happen, and is there any way I can stop it from happening, not including "never use the radio when the laptop is plugged in."

[Taslim]

Assuming you are charging the lappy from you 12 volt system it's probably the computer power supply feeding crap back spikes and crap into the power system. (not well put but..)

 

I sorted a similar prob by winding the power supply input lead three times though a ferrite toroid, a sort of small black doughnut you can get from Maplins etc.

 

It's a bit of a faff but worked.

 

Others with more knowledge than I will be along soon enough, no doubt, with simpler solutions and I will take notes.

 

Stay well.

[Starcoaster]

I thought it might be a 12v problem, so I tried it when I was connected to a shoreline on the 240 too and got the same result!

[Jim_UK]

Two possibilities, with suggestions to find which it is.

 

1. Laptop power supply is generating the issue. Electromagnetic Interference (EFI).

 

I get that on my DAB with a cheap Bilge pump, but only under certain circumstances.

 

If you look at the label (might be printed on rather than stuck on) on your laptop power supply. Now see if you can beg, borrow or steal a power supply with the same physical connection AND the same ratings. This could be tricky to do.

 

2. 'Noise' from the laptop power supply feeding back onto the mains circuit.

 

See if you can borrow one of those Surge/Spike 4 way gang extension cables. Alas the cheap ones may not be very good at smoothing out surges/spikes/noise.

[Bettie Boo]

Hi Star - sorry this won't help you much, but we've got a DAB radio and my laptop and have both going at the same time and experience no interference at all. I know Nothing about electrics, so just asking....is your wiring in good condition?

[KJT]

I had the same problem when running/charging my laptop using mains shore power or inverter. The DAB radio worked fine when the laptop was running on its internal battery, but the problem reappeared when on mains power. As an experiment I purchased a 12v power supply from Maplins which provided the 19 volts necessary and the problem disappeared. So I assume the problem lay with the mains transformer (the step down from 240v to the 19v my computer requires).

 

As an aside, I also got interference on the DAB radio from cheap LED lights which I had fitted. When I replaced them with more expensive ones the problem disappeared. I believe the replacements have an additional circuit which reduces the RF interference which was causing the problem.

 

Ken

[bizzard]

If the radio will work on its own batteries try them to eliminate if its airborne interference.

[andyb116]

Had a friend bring his solar powered DAB radio to our boat because it wouldn't work on his boat if the internal lights were on. (Early LED's). Tried it on ours with newer type LED's and no problem. Seems like the simplist things can block a DAB signal.

[Mac of Cygnet]

It doesn't have to be DAB. I get the same on my FM radio when the laptop is charging (both from the 12v system). I just stop charging until I've stopped listening. No big deal, but I can see that it would bother those who have the radio on all the time.

[Jim_UK]

If it proves too tricky or too much hassle to solve, you could always use your laptop to stream from t'internet (assuming you have an unmetered connection of course).

So, DAB radio for when laptop not in use and streaming when it is.

 

Of course it would be more satisfactory to solve the interference problem.

[Starcoaster]

I have to pay for the internet on my dongle, so streaming radio is not really an option.

The problem occurs the same with two different 240v chargers, and on the 12v.

I am currently charging the radio to see if it still happens when the radio is running on battery only.

Edited April 26, 2014 by Starcoaster

[twbm]

Just for devilment turn the wireless off on the laptop. In the unlikely event that it cures it it won't really help, but you'll know where to be looking.

[Starcoaster]

The wireless is off as I use the dongle. I haven't been moored in the spot where I can pickup free wifi for a bit, so I have the wifi turned off altogether at the moment to keep the laptop from scanning for networks.

[Chalky]

It's an RFI problem - Radio frequency interference. It can be either conducted or radiated. Conducted is when it travels through the wiring and radiated is when it travels through the air.

Most decent quality radios have an automatic gain control (AGC) on the front of the tuner to compensate for the quality of the radio reception. If you're in a good reception spot with a strong DAB signal then the AGC is turned right down and other radio frequency (RF) noise isn't a problem. If you're in a poor reception area then the AGC is turned right up and the radio can be more susceptable to any RF noise in the area. It could be that there's not a lot you can do since the receiver is very sensitive where you are. Improving the aerial on the receiver (e.g. external aerial) can help improve the signal strength and this could help.

 

Improving the earth/gnd/0v connection of the equipment can make a big difference. Often equipment will contain filters to take the RF noise and conduct it to gnd. If this gnd connection is poor then the gnd wire will just start to radiate and not do its job. The gnd needs to be as large a cable and as short as possible and ideally braid not cable. If the 12V laptop power supply is connected directly to the battery and the problem goes away then it suggests that the gnd cable may not be big enough. This and clip on ferrites (as mentioned earlier) would help with conducted RFI.

Re-reading you post it could also be the design of the charging circuit in the laptop. It should have passed an EMC test as part of the CE certification...

 

If its radiated RFI then an external aerial will help. Other fixed would involve adding RF shielding (re-design of electrical parts), changing circuit designs (re-design of electrical parts), adding filtering (re-design of parts). Apart from improving the antenna/ reception and moving things physically as far apart as possible there's not a lot you can do.

 

Problem is that EMC and RFI are complete black arts - I've dabbled in it and I have colleagues who do this as a full time job. What should work in theory and practice can be significantly different and it takes some sophicticated test equipment to sort it out.

[twbm]

... and be sure CE doesn't mean 'Chinese Export'. Not necessarily evidence of substandard goods, but misleading.

Edited April 28, 2014 by twbm