DAB splitter aerial relay

[captain Byrne]

OK - Got a new DAB radio and went for a splitter for the aerial. Trouble is it needs a 12v supply. If I wire it with a permanent live it's gonna drain the battery so the only option is to fit a relay, but given my limited, (ney hopeless) ability with electrics can someone please describe how I can fit a relay to supply 12V to the aerial splitter using the blue/white (low amp) feed from the radio.
Ta in advance.

[Jim San]

why does it have to be a permanent live - mine just powers up with the radio.

[captain Byrne]

The aerial doesn't have to be on a permanent live but the radio does as it's fed off the leisure battery. The only live feed from the radio is the blue/white wire. It's not strong enough to power the splitter well enough so that's why I think I need a relay. I may be wrong. How is your splitter wired Jim?

[CovKid]

Many of us don't keep the permanent live to radio as they're known for flattening batteries. It only takes a few seconds to find the station you want again each time anyway. Some have even fitted permanent off switches although in many cases removing facia does the same sort of thing.

[Oldiebut goodie]

The radio in my daughter's Punto will flatten the battery in just over a week. Mind you the battery is the size of a postage stamp!

[captain Byrne]

Thanks for the info. Does anyone know if a DAB splitter with a permanent 12v feed will be drawing any juice when the radio is turned off?

[Jim San]

How is your splitter wired Jim?

I don't know the specifics as I had it done for me.

I did a bit of thinking on mine (dangerous territory for me!!), my radio is powered from the leisure battery - i'm pretty sure about that as it lost all settings when I disconnected the LB's to change them. However, the radio only works when I have the ignition on !
So i'm a bit confused now. I had expected to be able to use the radio without having to have the keys in.

[ghost123uk]

The only live feed from the radio is the blue/white wire. It's not strong enough to power the splitter well enough so that's why I think I need a relay.

That blue/white wire is a 12v output lead that comes "live" only when the set is switched on. It is for stuff like electric aerials, amplified aerials, turning on sub woofer amps etc. It will have more than enough to supply the splitter, it's one of the reasons it's there

[CJH]

The only live feed from the radio is the blue/white wire. It's not strong enough to power the splitter well enough....

I'm no expert (in fact I know nothing about it), but that seems a bit surprising. If the blue/white wire is intended to power a motorised antenna, I would have thought it could supply enough current for a small antenna amplifier. Do you have the paperwork for the radio and the splitter? Does it say what current the blue/white wire can provide, and what current the amplifier draws?

Does anyone know if a DAB splitter with a permanent 12v feed will be drawing any juice when the radio is turned off?

Again, I'm no expert, but I would assume it will. I'm sure that the amplifier will be running regardless of whether there's a radio connected to the RF output. You could test this easily with an ammeter though, and it would answer the question in the last part of my first answer

[CJH]

Haha - as I was writing my reply I was thinking "this is a question for an electrical guru who's at a loose end". I didn't realise he'd posted just before me

[ghost123uk]

"electrical guru who's at a loose end"

Yep, that now looks like me this weekend

[captain Byrne]

I've sorted it - The blue/white 12v from the radio is a very low amperage designed to trigger a relay. I'm pretty sure if there was a permanent live to the splitter it would quickly drain the battery so I've just fitted a relay to give the splitter its full wack of power only when the radio is turned on. Seems to be working fine, fingers crossed.

[ghost123uk]

I bet the relay pulls more power than the amp in the splitter does

[captain Byrne]

I've read a few articles about folk who wire up their DAB splitters with the blue/white from the radio and get very poor reception. Doesn't surprise me as it's only 300mA. Fitting a relay gives the splitter its full whack of power so it should work how it's meant to.

[CovKid]

Rather than hypothesise, perhaps best to try.