Radio interference, 1 station only

[HughJarsse]

Hi all,
Have a multipla, 2005 model (nosejobby) with the factory fitted CD/radio.
All works OK except for just 1 local station that suffer from interference when engine running.
All other national stations (radio 1-2-3-4 and classic, etc) work no problem. Strange that this local station which broadcasts on 2 different frequencies (96.1 and 103.8 fm) suffers and is the only one??
Wondered if anyone else has had this, and has any answers.
Could understand if all stations suffered, but just this one, and on both frequescies??? (have tried all the settings in the menu's to see if they make any difference, ie: DX/LO, & hicut off/on etc)

 

[varesecrazy]

Weird indeed.. is it the crackle of ht leads.. or something else?

 

[g8rpi]

Hi all,
Have a multipla, 2005 model (nosejobby) with the factory fitted CD/radio.
All works OK except for just 1 local station that suffer from interference when engine running.
All other national stations (radio 1-2-3-4 and classic, etc) work no problem. Strange that this local station which broadcasts on 2 different frequencies (96.1 and 103.8 fm) suffers and is the only one??
Wondered if anyone else has had this, and has any answers.
Could understand if all stations suffered, but just this one, and on both frequescies??? (have tried all the settings in the menu's to see if they make any difference, ie: DX/LO, & hicut off/on etc)

I missed this te first time around.

Do you have a USB cellphone charger, GPS power lead or similar that plug into the lighter / accessory socket? I've found that most of these, even "quality" ones like Tom Tom emit interference in the VHF band. Local stations are more susceptable as the transmitter power levels, and thus signal levels, are lower.

If you have one try unplugging it. There are muliple emissions spaced at the switching frequency of the regulator (yes I have a spectrum analyser, five actually). A bit of investigation showed that the exact culprit is the steering diode which has fast turn off. A few picofarads of capacitance across the diode sorted it.



Robert G8RPI.

 

[HughJarsse]

Weird indeed.. is it the crackle of ht leads.. or something else?

Vehicle is diesel, so no HT leads, sadly, otherwise that would have been my first thought...

 

[HughJarsse]

I missed this te first time around.

Do you have a USB cellphone charger, GPS power lead or similar that plug into the lighter / accessory socket? I've found that most of these, even "quality" ones like Tom Tom emit interference in the VHF band. Local stations are more susceptable as the transmitter power levels, and thus signal levels, are lower.

If you have one try unplugging it. There are muliple emissions spaced at the switching frequency of the regulator (yes I have a spectrum analyser, five actually). A bit of investigation showed that the exact culprit is the steering diode which has fast turn off. A few picofarads of capacitance across the diode sorted it.



Robert G8RPI.

Rob, it appears you may be correct, as have had a dash camera 'hard wired' into the car, and, according to the guy that fitted it, he fitted a USB power adapter into the ignition switched wiring, (further investigation shows it fitted onto the 'aux' power socket, behind the dash beside radio) this has been properly spliced (soldered) into the loom, and covered in heat shrink wrap.
Further testing established the fact that it was the dash cam itself, not the usb adapter, causing the interference. Disconnecting the dash cam from the usb plug, radio works correctly. Plug dash cam in....interference.
So, tried the usb adapter with my phone.....and radio works correctly whilst phone charging on the usb plug. So, appears that the dash cam is the culprit. (also tried my sat nav on the usb plug, and again, radio and sat nav work correctly together, the sat nav is used with the cigarette lighter socket adapter, separate from the dash cam)
So, now have to decide whether to ditch the dash cam, or find another solution to the interference? Bit of a nuisance ..
(Just to make sure I was correct it was the dashcam, tried it in daughters Punto with the sat nav adapter in cigarette lighter, and....Yup, radio plays up on local frequencies!! with dash cam plugged in, but radio works perfectly when dashcam unplugged.)