Dashcam interference with DAB - any advice?

[slicendice]

I've recently purchased a dashcam for my g/f's Polo and having heard that the rear cam can sometimes cause interference with DAB radio, I've been looking at ferrite cores which I believe can help restrict this.

 

Trouble is, I know less than nothing about it so I'm shooting blind to a large degree. From what I understand, DAB operates at around the 175-240MHz frequency range (as detailed here), so this is the range that would need handling.

 

If that's the case, are there any "recommended" options to go for? Has anyone who's had this issue used one with any success?

 

I've found a couple of options online by retailers who state they are specifically for this purpose:

• this one states that it has "an impedance of 33Ω at 25MHz and 92Ω at 100MHz". Given they're advertising it as specifically for preventing DAB interference, I would have hoped that was suitable, but it seems to operate outside the DAB frequency range? Or have I completely misunderstood that? (More than likely! 😂)
• this one is also advertised as being specifically for preventing DAB interference, but gives no technical details

 

Or would it make more sense to buy from an electrical specialist like this (which I'm sure are probably the same as the above two but slightly cheaper)?

 

Thanks!

Edited 2 December, 2019 by slicendice

[Paulius55]

I would bet that it is not the dashcam but the dashcam power supply. Cheap and simple power supplies just chop the voltage rapidly to get from 12v to 5v and that generates radio waves that can knock the DAB out. I found that the best power supply is an original one from TomTom for their satnavs. The power supply is more sophisticated and gives a smooth 5v which does not affect the DAB signal. 

[ncd]

I had the same problem with my radio when I fitted my Dashcam. I put a couple of ferrite cores on the dash cam power cable and the problem was solved. I put one near the camera and one near the start of the other end of the power cable. Problem was solved with a cheap fix.

[Aspman]

It's the power supply. I had this with a cheaper dashcam. I guess the supply is unshielded. I don't know if ferrite blocks will do much. I switched to a branded camera (Sandisc). Problem gone.

[MickA]

I've had similar problems with my cheapo Chinese dash cam. I've also got a cheapo DAB all in one unit (plug-in) again Chinese. Come to the conclusion they don't like one another, especially the DAB unit it just goes off when the dash cam fires up. Tried ferrites but no good, I've had it hardwired too but that was just as bad as it was a cheap kit I bought. They both of course work fine on their own but no together.

That was in my MX-5, I put the cheap dash cam in my Toledo with a built-in DAB head unit (Amundsen) and it's fine absolutely no conflict. I've since chucked it in the cupboard and bought myself two Nextbase cams in the sales, they work fine in either car, DAB works fine in both too👍

[VWD]

As said- my first port of call would be the 12-5 convertor. Easy way to find out. Get hold of one of the plug in 12v- USB convertors. Chances are that it will be based on a 7805 IC( most I've opened were), which does not rely on  chopping the DC to convert to a near AC square wave. Noise gone, chances are that it's the cheap (and nasty ) dashcam voltage convertor.

Problem is that a square wave consists of many harmonics ( multiples of the original frequency ). Adding ferrites to the exterior can cure this sort of problem, but in the worst case you need a PI filter consisting of a series RF inductor ( cheaper models use a resistor )with capacitors across the supply.

It might seem complicated, but even a home brew 7805 convertor is easy to make . It needs a 7805 IC ( 1A or 1.5A version) , which has three terminals- in out and common. Add to this a couple of smoothing capacitors. In cap =.33uF connected across the in and common, OUT CAP =.1uF connected across the out and common. If the IC gets warm to the touch, add a heatsink.

 

[robt100]

Anything electrical plays havoc with the DAB in the Van, then again, it was a cheap DAB ariel. Even using the wipers triggers it to momentarily stop working

[WaveyDavey]

I'd try a couple of ferrite cores on the power cable to the camera as a first attempt. They can be had for about 50p each.

 

I put one at each end of my dashcam power lead the other week after replacing my failed Columbus unit in my Superb with a newer unit that had DAB as well as FM/AM. Went from pretty much no DAB stations to everything available.

Edited 17 December, 2019 by WaveyDavey