UHF Radio, FM Radio receiving Interference from Dash Cam

Submitted: Sunday, Sep 18, 2011 at 13:45
ThreadID: 89095 Views:5259 Replies:2 FollowUps:1
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I have an ORION UHF100 receiving interference from a HD DVR Dash Cam on Channels 9 & 10. All other channels work fine.

I also have a PIONEER FM MP3 player receiving interference from the dash cam as well on FM.

The UHF is directly connected to the car battery + Terminal, and grounded to the chassis. The Coax for the UHF runs inside the car door frame on the right, and the FM aerial is factory installed on the left.

When the DVR powers on and records, the interference is evident - and is the same issue whether the DVR is running on its own battery or plugged into the car's 12V cigarette lighter.

It's obviously radiation from the DVR, so I need advice in how to block the signals even partially to stop this nuisance.

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Reply By: Bob Y. - Qld - Sunday, Sep 18, 2011 at 21:21

Sunday, Sep 18, 2011 at 21:21

Am no electronic guru, but reckon you might need to peruse JAYCAR Electronics website, and look for either:

Toroid Cores LO-1230 to LO-1238

Powdered Iron Cores LO-1242 to LO-1246 or

Round Cable Suppresion Sleeves LF-1290 to LF-1294

The go is to wrap as many turns of the power lead as possible, through the Core, and that may reduce RFI/EMF. Also I'd hook the -ve onto the -ve terminal of battery as well, rather than the chassis. Don't ask me why, just that it worked with HF radios, years ago. Have also seen techs twist the power cable, for its entire length, which also reduces RF induction.

You could even wrap the co-ax, to both UHF & FM radio, through a couple of these cores, if you can't kill the interference.

If the interference is only on Ch 9 & 10, then that's easy to fix. The FM noise is more important, so I'd be concentrating on that. Nothing worse than hash over the top of U2 or Coldplay!!!

Let us know how you get on. Those cores are fairly brittle to, so break easily if they're dropped.

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Can't remember most of it.

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AnswerID: 465425

Follow Up By: rancox265 - Monday, Sep 19, 2011 at 18:46

Monday, Sep 19, 2011 at 18:46

Thanks for your reply - and it seems that you know more about these setups than most "professionals" here in town. The Toroid Coils are often used on Laptop Computer applications to reduce "hum" and Wifi interference issues, so that actually makes sense - to attach one Toroid to the connecting end of the UHF, and another to the connecting end to the FM aerial.

We'll see how that goes.
FollowupID: 739515

Reply By: rancox265 - Tuesday, Sep 20, 2011 at 16:02

Tuesday, Sep 20, 2011 at 16:02
Easy, temporary fix until I can find a more permanent solution in blocking the interference - I had put Channels 6, 9 & 10 in "Quiet Mode" effectively making these three channels useless and the radio ignores the interference noise from the dash cam.

I will be getting the cores next week, and will try wrapping them around the connection point ends of the coax aerials on the UHF and the FM Stereo, to see if that solves the problem.

As for Channels 6, 9 & 10 there is no radio traffic anyhow on those channels so I doubt I'll miss much. Most traffic is on our family channel 19, local call 11, travel 29 and trucks 40.
AnswerID: 465571

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