Rear de-mister affecting radio

[Lusky]

Here's an interesting one. Has anyone else experienced this or know why it Happens?
When the rear de-mist button is pressed to heat up and clear the rear windscreen, the FM signal on the radio is significantly reduced to the point where it sounds as if its no longer tuned correctly / isn't receiving enough of a signal?

[gloucester]

I don't recall experiencing that - but I rarely used the HRW and usually listened to DAB not FM.

[calnorth]

This stuff works largely on a wing and a prayer and it does happen. The vehicle is very close to the ground to which antenna signal pick up is much reduced over roof antennas, particularly houses. Its called signal to noise ratio... S/N. More S the better. Low level radio signals can enable noise in the environment to dominate/interfere. It is actually a function of the receiver to increase gain for weak radio signals. Thats called Automatic Gain Control (AGC).

In the case of the rear screen it could be that poor earthing/corroded wiring causes a power line to pass vehicle communication signals to the screen embedded heater lines. That is very close to the embedded antenna structure. So its a look at the cables and plugs/sockets in that area before condemning the screen.

There is an FM/DAB radio pre amplifier in there usually which could also contribute to reception problems. It'll amplify the undesired noise as well. If signal/noise overloaded it will generate a mass of distortion...much noise!

[madlogan]

I get something very similar. When I turn the rear de-mister on I lose DAB signal. As soon as I turn the de-mister off the signal comes back!

[calnorth]

I get something very similar. When I turn the rear de-mister on I lose DAB signal. As soon as I turn the de-mister off the signal comes back!

Try the same thing when on VHF FM. DAB will cut off completely if it determines that signal is weak. VHF FM will simply get noisy.