Supressing noise from 12v-5v converter on VHF

[KC8UQX]

I finally managed to track down what was causing terrible receive in my mobile installation: It's the power supply for my dash cam (this one: http://www.amazon.com/Hard-Wire-Mic...2979992&sr=8-4&keywords=dash+cam+hardwire+kit ).

When the power supply is active, I get a LOT of static on 2m, and 440 receive is compromised. 440 isn't terrible, but there's a significant difference in receive sensitivity when it's disconnected from vehicle power. 2m is basically useless. I get of a lot of S7+ static across the entire band.

I have some ferrite chokes coming, but I have a few questions:
1) Where would be "ideal" placement? I'm thinking run a few turns of the wires through the chokes as close to the power supply as possible.
2) What else can I do to suppress the noise? Or should I even bother? Would I be better off just replacing the whole unit?

 

[popnokick]

It's likely a very low cost switching supply with inadequate filtering. You are going to spend a lot of time and money trying to eliminate the RFI via external devices. Replace the whole thing with something that has a better-filtered DC supply.

 

[n4yek]

Here is a question, is it the power supply causing the noise OR is it the dash cam causing the noise?
Something you might want to find out if you can.

 

[popnokick]

Could be either, but you are the one who will need to find out. It looks like the dash cam is powered with a Micro USB connection. So disconnect the Micro USB from the cam and see if the noise is still there with the cam off. If so, it's the DC supply. If not, then plug in a different 12V DC supply to your cigarette lighter socket with another Micro USB cable. Make sure you use a cigarette lighter USB charger that doesn't already have an RFI problem.... that a very common thing. Use the "good" USB power supply and turn on the camera. If the RFI appears, you know the problem is the cam itself.

 

[KC8UQX]

Here is a question, is it the power supply causing the noise OR is it the dash cam causing the noise?
Something you might want to find out if you can.

It's definitely the power supply. I unplugged the camera, but left the power supply plugged in, and still had the noise.

 

[prcguy]

Mix 43 ferrite is good for suppressing VHF RF signals and a few turns of the cigarette lighter cable through a medium size ferrite bead right at the output of the converter is a good place to start. Find a bead that is big enough to pass the cable with plug a few times and start with 2 turns then test for noise and keep adding turns until you find the best compromise.

If the interference is mostly generated on the 12V side you can usually unplug the wires from the rear of a cigarette lighter socked and pass them through several ferrite beads and plug the wires back in.
prcguy