radio wiring

[richardh10]

As my daughter is scrapping her car I decided I would nick the radio for the boat. Saves buying one. So I pulled it out (the radio), got a wiring diagram from Sony and found a yellow wire for continuous power supply and a red one for switched power. Help. Which one do I use, and do I ignore the other one?

Cheers

 

[Elemental]

As my daughter is scrapping her car I decided I would nick the radio for the boat. Saves buying one. So I pulled it out (the radio), got a wiring diagram from Sony and found a yellow wire for continuous power supply and a red one for switched power. Help. Which one do I use, and do I ignore the other one?

Cheers

The yellow one should be connected to the battery directly and provides a low power feed to keep the radio preset channels stored. You can ignore it. The red should go through your normal switching circuitry.

I didn't fancy a constant current drain so I left the yellow off. When I isolate the batteries, my presets are therefore lost.

 

[Cardo]

My radio was similar and the idea is to wire as the poster above has stated. Instructions said that if I didn't want to have a continuous supply then to simply splice the two wires together and connect them to the same power supply.

 

[richardh10]

Thanks for that. I thought that must be the case but glad I checked. Not too bothered about presets.

Cheers

 

[Littlelegs]

The continuous feed is just for the memory but if you don't want to hook it up to the main battery but do still want to preserve your presets you could think about getting an old 12V alarm battery (for example). The current drain would be so low, it'd last for ages or you could hook that continuous feed up to a little 12v solar panel.

Or then again, take the real-world approach & just manually scan for a radio station whenever you're using it!

 

[richardh10]

One other thing. For the aerial, is it possible to splice into the one for the vhf radio, or does it need a seperate one

Cheers

 

[john_morris_uk]

It needs a separate one. You might damage the VHF, and you certainly stand a chance of damaging the car radio if you transmit if the radio is connected to the same ariel as well. There are 'splitters' available that allow you to share one antenna, but I always think that a separate antenna for each bit of kit is the better option. Almost any bit of wire will do for the car radio.

 

[Elemental]

There are 'splitters' available that allow you to share one antenna, but I always think that a separate antenna for each bit of kit is the better option. Almost any bit of wire will do for the car radio.

There was a 'splitter' in the circuit when I got the boat. Useless. Did better with a length of wire. Subsequently changed it for an internal antenna.

Do not attempt to splice onto the VHF antenna....

 

[ghostlymoron]

One other thing. For the aerial, is it possible to splice into the one for the vhf radio, or does it need a seperate one

Cheers

Most car radios will work OK with an internal aerial. Mine is just lying in the locker behind a settee berth - seems to work all right.

 

[theoldsalt]

On most modern car radios if the continuous power supply is interupted (eg battery disconnected for car maintenance or battery replacement) then not only will the presets be lost but the radio will cease to work until the security number unique to that radio is reloaded. This is an anti-theft feature.

So the yellow wire needs to go directly to the battery and not through the boat's battery isolator switch. The drain is very low as cars can be left for months and there is still enough power in a good battery to start the engine.

Some people don't like a continuous drain on the boat battery, so a modern car radio is not really suitable.

 

[richardh10]

Thanks all

 

[Cardo]

One other thing. For the aerial, is it possible to splice into the one for the vhf radio, or does it need a seperate one

Cheers

I got one of these - http://www.pacificaerials.co.nz/MarineProducts/P7101VHFAMFMBroadcastBandSplitter.aspx

It seems to do the job. Though I haven't had to use the VHF in anger, yet.

 

[Littlelegs]

One other thing. For the aerial, is it possible to splice into the one for the vhf radio, or does it need a seperate one

Cheers

Don't even think about it! Particularly if you were thinking of literally splicing & swaddling with insulation tape

Why? well firstly you've broken the insulation on the co-ax for the VHF. That lets moisture in and it will corrode very quickly (unless you really know what you're doing with RF connections). That will lead to impedance matching problems for the VHF transceiver, potentially degrading RX performance and certainly likely to reduce performance & potentially damage the transmitter output stage.

Secondly, you've just hooked up a receiver, expecting millionths of a watt of radio signal, directly to the output of a transmitter putting out Watts of radio power. It's not going to end well! Professional grade comms kit often has additional protection circuitry to help deal with such things but a standard car radio won't - it'll almost certainly become permanently deaf after you transmit for the first time!

The spitters that are marketed purport to have protection built in but I really wouldn't touch them with a barge pole. For VHF programme reception then a cheap aerial from a car parts palce would be fine (how a tax-disc style one to go on any convenient glass?) and when it comes to your marine VHF, keep the aerial high, keep the coax in good condition and don't introduce joints into the cable run if it can be avoided, each one introduces attenuation.

 

[st599]

Why would you put a point of failure into a safety critical system?

 

[Elemental]

Why would you put a point of failure into a safety critical system?

+1

 

[Dave_Seager]

If you only connect power to the red wire through your isolator then you will probably lose your presets every time you switch the radio off. If you join them both to the power supply through the isolator then the presets will be retained until you turn the isolator off. This way you can have the benefit of keeping your settings during a cruise but still turn everything off when you leave the boat for longer periods.

 

[theoldsalt]

Not true. As I previously stated, each time the power is disconnected a security code will have to be entered before the radio will work when the supply is reconnected. This will happen every time unless the continuous power wire is kept connected directly to the battery.

 

[Elemental]

Not true. As I previously stated, each time the power is disconnected a security code will have to be entered before the radio will work when the supply is reconnected. This will happen every time unless the continuous power wire is kept connected directly to the battery.

Not true. My new (well, 18 month old) Halfords job works just fine as posted (red connected, yellow left off). All behind the isolator.

 

[theoldsalt]

I agree, some after market fit radios do not require a security code, most manufactures' fit radios in cars do, however.

 

[Plevier]

Don't forget that if you go for the permanent (unswitched) live connection to the radio, the radio negative connection will also need to go to battery side of the negative isolator if you have one.