Annoying issue with dashcam and dab windscreen aerial

Jamesyboyjim · 6 Mar 2016 at 14:41

Hi all, I have an aftermarket Sony headunit in my car, it has a dab tuner which I am using with one of those stick on windshield aerials, this works perfectly well but I have recently got a dashcam which connects from the camera via USB to the cigarette 12v port.

Trouble is, when the camera is on and the USB lead connected it interferes massively with the radio, even if it isn't connected the 12v socket. I have tried re-routing the cable but it seems that if it is even a few cm away from the windscreen it interferes.

im guessing whatever current that passes through the lead interferes with the aerial but does anyone have any idea what I can do to stop this?

iaind · 6 Mar 2016 at 14:43

Try a ferrite core round the USB cable

Jamesyboyjim · 6 Mar 2016 at 21:29

iaind said:
Try a ferrite core round the USB cable

What is that if you don't mind me asking? I'll have a Google and see what comes up

iaind · 7 Mar 2016 at 07:19

Look at any analogue cable and a lot of DC power supply connectors - VGA for example, notice the big lumps on the end of the cable before the connector? Those are ferrite cores, there to prevent the signals causing interference on other cables nearby. You can buy them, just clip one onto the end of the USB cable.

The cable will have 12v on it when it's connected to the camera or socket, but this won't be a completely clean flat voltage, it will vary slightly picking up noise from the camera internals (let's face it, those won't be the highest quality electronics) or the alternator in the car. DAB is going to be really sensitive so having what is basically a transmitter right next to the antenna won't do it much good.

The other option is to replace the antenna with a roof mount one, but for a couple of quid I'd try the simple fix first

https://www.ebay.co.uk/ulk/itm/171988630554

Jamesyboyjim · 7 Mar 2016 at 08:33

iaind said:
Look at any analogue cable and a lot of DC power supply connectors - VGA for example, notice the big lumps on the end of the cable before the connector? Those are ferrite cores, there to prevent the signals causing interference on other cables nearby. You can buy them, just clip one onto the end of the USB cable.

The cable will have 12v on it when it's connected to the camera or socket, but this won't be a completely clean flat voltage, it will vary slightly picking up noise from the camera internals (let's face it, those won't be the highest quality electronics) or the alternator in the car. DAB is going to be really sensitive so having what is basically a transmitter right next to the antenna won't do it much good.

The other option is to replace the antenna with a roof mount one, but for a couple of quid I'd try the simple fix first

https://www.ebay.co.uk/ulk/itm/171988630554

Really helpful response Iain, thank you

I will order from the link provided and see what happens

An external aerial would be ideal but the only ones I could see were those magnetic ones, I'd have to run the cable through the door or something. Not great!

iaind · 7 Mar 2016 at 08:36

Just double check the size is right, I liked as an example

Jamesyboyjim · 7 Mar 2016 at 08:45

iaind said:
Just double check the size is right, I liked as an example

Now you mention it, 3.5mm seems a little small, not sure the size required though, its just a standard (I use that term loosely) mini usb lead, not extra thick or anything.

IAmATeaf · 7 Mar 2016 at 10:00

3.5mm is the cable diameter, I'd suspect that the cable you have won't be much larger/smaller?

Jamesyboyjim · 7 Mar 2016 at 10:14

IAmATeaf said:
3.5mm is the cable diameter, I'd suspect that the cable you have won't be much larger/smaller?

When I think of 3.5mm, I think of a headphone port which seems a little small. I'll have to physically compare the cable.

IAmATeaf · 7 Mar 2016 at 10:28

Jamesyboyjim said:
When I think of 3.5mm, I think of a headphone port which seems a little small. I'll have to physically compare the cable.

A typical USB phone charger cable will for example be around 3.5mm in diameter, cable from an external mouse would say be slighly larger at around 3.75mm.

Jamesyboyjim · 7 Mar 2016 at 10:55

IAmATeaf said:
A typical USB phone charger cable will for example be around 3.5mm in diameter, cable from an external mouse would say be slighly larger at around 3.75mm.

The cable looks pretty typical, so I'd hazard a guess you're right

breadturbo · 7 Mar 2016 at 12:06

I used one from an old ps2 pad I had laying around, did the trick.
The 360 one also has them.

Phemo · 7 Mar 2016 at 12:19

I had a similar issue with a cheap eBay 2 port USB car charger. Whenever I plugged it in it would kill my digital radio signal completely and most analogue stations would be worse than usual. I used this charger tucked away in a second socket in the glovebox for powering my satnav and dashcam hard wired so it wasn't ideal. In the end I just bought an Anker 2 port USB charger and all is good.

So I'd suggest trying one of those and just using a USB cable to power your cam.

Jamesyboyjim · 7 Mar 2016 at 12:20

breadturbo said:
I used one from an old ps2 pad I had laying around, did the trick.
The 360 one also has them.

Are they removable from the controllers? It would be interesting to test one to get the size right.

Jamesyboyjim · 7 Mar 2016 at 13:21

Phemo said:
I had a similar issue with a cheap eBay 2 port USB car charger. Whenever I plugged it in it would kill my digital radio signal completely and most analogue stations would be worse than usual. I used this charger tucked away in a second socket in the glovebox for powering my satnav and dashcam hard wired so it wasn't ideal. In the end I just bought an Anker 2 port USB charger and all is good.

So I'd suggest trying one of those and just using a USB cable to power your cam.

Thanks mate, I have ordered a few ferrite clamps so I'll try them, failing that I'll get one of those chargers and a decent usb cable and see if that makes a difference.

As the interference is still there without the cigarette adaptor being connected, I'm thinking this issue is whatever voltage/signal the camera sends down the cable as the issue is only when the camera is on with the lead plugged into it.

The camera operates alongside the radio with no lead plugged in just from the battery.

breadturbo · 7 Mar 2016 at 13:22

Usually yes, a sharp edge and they turn out like this pic I kicked from google

iaind · 7 Mar 2016 at 13:29

Jamesyboyjim said:
Thanks mate, I have ordered a few ferrite clamps so I'll try them, failing that I'll get one of those chargers and a decent usb cable and see if that makes a difference.

As the interference is still there without the cigarette adaptor being connected, I'm thinking this issue is whatever voltage/signal the camera sends down the cable as the issue is only when the camera is on with the lead plugged into it.

The camera operates alongside the radio with no lead plugged in just from the battery.

You might actually find that connecting it will be better, especially with a half decent charger, as it'll be properly grounded to the car body

Jamesyboyjim · 7 Mar 2016 at 14:38

iaind said:
You might actually find that connecting it will be better, especially with a half decent charger, as it'll be properly grounded to the car body

What do you mean by connecting it matey?

iaind · 7 Mar 2016 at 14:56

Plugging it into the charger

Jamesyboyjim · 7 Mar 2016 at 15:03

iaind said:
Plugging it into the charger

Ah, you mean getting a decent usb cigarette charger adaptor thing and using a usb lead rather than using the supplied usb to cigarette adaptor provided?