Fitting a DAB car radio. Do I need an earth?

[Refueler]

No, when we turned it up to test it.
Found some blurb for a Pioneer radio, wants a 15A fuse in the 'permanent' supply, that's a shitload of memory retention.
Not saying all radios are the same.
There is some ambiguity in the pin definitions of the DIN connectors that many radios/vehicles use.

I can imagine that some radios may use the permanent supply via a switching circuit. That is full power available but when radio switched off - power routes through a limiter so only a very small current passes to maintain settings. Switch on and that same power input now routes without limiter to power the radio fully.
That would be the only way I could see it working - otherwise you'd either lose all settings when you switch off ... or car battery would be dead very quick.

 

[Refueler]

Ah, I see what you mean. I was thinking about why you would want a permanent supply that wasn't switched.

Personally I feel that non-essential items on boats should always have a breaker to turn them off completely, which would mean picking the head unit carefully for stuff like PINs, clocks and my personal bugbear - demo modes.

I generally agree but have to admit that the radio I have in my boat is wired direct but with suitable fuse in the +ve feed. Its always powered for settings and switch on delivers the goods. Its a pop-off front radio but stays in place usually.

 

[lw395]

FWIW, the DAB module may remember the channels without any 12V supply.
But my only DAB radios are quite old now. I gave up on it when Planet Rock got too many adverts, then moved somewhere where reception is terrible.
I found my old DAB portable last month in a loft clear out, fired it up, it remembered 'Planet Rock' but couldn't find it....

 

[Refueler]

FWIW, the DAB module may remember the channels without any 12V supply.
But my only DAB radios are quite old now. I gave up on it when Planet Rock got too many adverts, then moved somewhere where reception is terrible.
I found my old DAB portable last month in a loft clear out, fired it up, it remembered 'Planet Rock' but couldn't find it....

Like a computer - I can imagine that some may have a small 'button' battery or capacitor to keep settings alive ... or even a small memory module similar to a memory stick ? But with the two lead system - I can easily imagine they did away with such.

 

[lw395]

Like a computer - I can imagine that some may have a small 'button' battery or capacitor to keep settings alive ... or even a small memory module similar to a memory stick ? But with the two lead system - I can easily imagine they did away with such.

The two-lead system pre-dates DAB in cars by a fair bit.

 

[Refueler]

The two-lead system pre-dates DAB in cars by a fair bit.

Is that why you still buy many radios of ALL type with two leads ????? I would suggest that there are probably more two lead radios out there than not !