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

[joyfull]

Just about to fit a DAB car stereo. I have the dedicated DAB aerial.

Is it ok with just positive and negative into the switch panel. Should I also wire in an earth (if so where to?)

 

[FlyingGoose]

When I wired mine it was only positive , negative, with a fuse close to the radio, which might already be there , then I put it onto my switch panel with a fuse , probably over kill .

 

[PaulRainbow]

When I wired mine it was only positive , negative, with a fuse close to the radio, which might already be there , then I put it onto my switch panel with a fuse , probably over kill .

One fuse, close to the supply. The one near the radios is superfluous .

 

[FlyingGoose]

One fuse, close to the supply. The one near the radios is superfluous .

Agreed I was pointing out that a lot of Radios already have the blade fuse in their casing as a manufacturer practice .
my post was referring to the overkill of 2 fuses , but I prefer my own fuse to protect the wire run, and I assume the fuse at the radio is to protect the sensitive electronics.
All cars have a radio fuse separate to the radio fuse as well , although, I suspect not all radios have this blade fuse for what ever reason, but mine did

 

[lw395]

The 'earth' that matters is the outer of the coax to the aerial, which needs to be connected properly at the radio and the aerial, but need not be connected to anything else outside the radio.

A lot of radios have two +ve supplies, one switched and one permanent.

 

[Laysula]

A lot of radios have two +ve supplies, one switched and one permanent.

Mine has two +ve supplies, one to power the radio wired direct to the circuit breaker board and one to retain the radio tuning to save having to retune it everytime the power is disconnected. So my second power lead is wired direct to the battery through it's own inline fuse.

 

[PaulRainbow]

Agreed I was pointing out that a lot of Radios already have the blade fuse in their casing as a manufacturer practice .

my post was referring to the overkill of 2 fuses , but I prefer my own fuse to protect the wire run, and I assume the fuse at the radio is to protect the sensitive electronics.
All cars have a radio fuse separate to the radio fuse as well , although, I suspect not all radios have this blade fuse for what ever reason, but mine did

You said "with a fuse close to the radio, which might already be there , then I put it onto my switch panel with a fuse ".

To be clear, a fuse should be fitted at the supply end of any circuit. There is no need to fit additional fuses elsewhere. In the case of a radio with an integral blade fuse, you obviously have to leave that in place.

Bit of thread drift...... A lot of marine electronics come with inline fuses, which i find annoying. They will almost always end up a distance from the supply and invariably behind a panel. You also end up with 50,000 different types/sizes/styles/current ratings of fuses in 50,000 different places. As a matter of course i remove all inline fuses and use a single style of fuse in central locations.

 

[[163233]]

The 'earth' that matters is the outer of the coax to the aerial, which needs to be connected properly at the radio and the aerial, but need not be connected to anything else outside the radio.

A lot of radios have two +ve supplies, one switched and one permanent.

Does that mean connecting the coax to the earth terminal on the radio?

I vaguely recall in a distant past electronics course than an actual ground in the soil makes a big difference to radio reception. But I may have entirely misunderstood. Obviously this is difficult with cars.

 

[anoccasionalyachtsman]

Does that mean connecting the coax to the earth terminal on the radio?

I vaguely recall in a distant past electronics course than an actual ground in the soil makes a big difference to radio reception. But I may have entirely misunderstood. Obviously this is difficult with cars.

The aerial coax should already be internally grounded to the radio chassis.

 

[[163233]]

The aerial coax should already be internally grounded to the radio chassis.

And what should the chassis be connected to?

 

[lw395]

Mine has two +ve supplies, one to power the radio wired direct to the circuit breaker board and one to retain the radio tuning to save having to retune it everytime the power is disconnected. So my second power lead is wired direct to the battery through it's own inline fuse.

Very often it is the permanent supply which supplies the main power, you can get caught out thinking it's only a milliamp or two to retain the tuning memory.

 

[john_morris_uk]

And what should the chassis be connected to?

The negative of the battery.
Ground connections for antenna performance in this context is complex. It’s often more about reducing interference than actual ability to pull in a signal
My advice would be to just connect the power up and try it. If it works, stop worrying.

 

[[163233]]

My advice would be to just connect the power up and try it. If it works, stop worrying.

That does tend to be my approach to these things as well.

 

[lw395]

And what should the chassis be connected to?

It can take a long time to answer that question. It will almost certainly be DC zero volts, but the detail of how it gets back to the battery is a big variable if there are issues with interference from other kit. If it works well with the set only grounded by the black wire, then perhaps it's best to leave any direct chassis connection open.

 

[anoccasionalyachtsman]

And what should the chassis be connected to?

Modern cars generally hold the radio in a plastic structure - the only ground is the negative power connection. The 'main aerial' coax screen doesn't even get grounded in my cars. (The DAB aerial I have does though).

 

[FlyingGoose]

You said "with a fuse close to the radio, which might already be there , then I put it onto my switch panel with a fuse ".

To be clear, a fuse should be fitted at the supply end of any circuit. There is no need to fit additional fuses elsewhere. In the case of a radio with an integral blade fuse, you obviously have to leave that in place.

Bit of thread drift...... A lot of marine electronics come with inline fuses, which i find annoying. They will almost always end up a distance from the supply and invariably behind a panel. You also end up with 50,000 different types/sizes/styles/current ratings of fuses in 50,000 different places. As a matter of course i remove all inline fuses and use a single style of fuse in central locations.

Well your are right I Should have said at the radio itself , I though that the word Close would have been obvious to see the actually fuse , but then we must expect everyone is a bit daft around here

 

[PaulRainbow]

Just about to fit a DAB car stereo. I have the dedicated DAB aerial.

Is it ok with just positive and negative into the switch panel. Should I also wire in an earth (if so where to?)

Connect positive to a fused supply (might be two positives, one permanent, one switched, consult radio instructions). Connect negative to negative busbar etc. Plug aerial in. Turn radio on, pour glass of beer. Sit back with feet up, listen to music, drink beer. ?

 

[tmtracey]

So if there’s two positives (permanent and switched), should they be connected together and put on single fuse? And what size fuse?
I’m just about to start installing mine.

 

[tmtracey]

It would be basic car radio with 4 x 50w speakers. Thanks.

 

[[163233]]

So if there’s two positives (permanent and switched), should they be connected together and put on single fuse? And what size fuse?
I’m just about to start installing mine.

The perm probably maintains the clock and perhaps the state of the system. Mine turns on to a demo page which you have to cancel every time for instance, if you turn it off with the switch on the radio it comes back on normally. So it depends what it does when the power comes on first time.