Radio reception crap/ worse when motor is cold

[mudski]

So I've put up with this for long enough. The head unit is a chit Eonon unit, but I just need a radio and a screen for my reverse camera. And Blutooth. As of late I have noticed the radio reception getting worse. I just really noticed it today that it was really bad when the motor wasn't at optimum temps. But after driving the car for a while the radio reception was much better. Probably at around 90% of what it should be.
I did notice also the reception got better when the revs dropped.

Any ideas what this may be?

[TPC]

What is the condition of your battery or batteries?
A dodgy main or aux battery can create problems for radio reception which will improve as the battery charges.
Does it get worse if you put the headlights on?

[Mike02Ti]

Earth gone bad maybe? Either on the head unit itself or the antenna.
Did you use an adapter for the antenna plug into the back of the unit?

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[mudski]

What is the condition of your battery or batteries?
A dodgy main or aux battery can create problems for radio reception which will improve as the battery charges.
Does it get worse if you put the headlights on?

Haven't tred with the headlights mate. I will give it a crack tomorrow. The batteries aren't that old and get a good top up charge every few months.

Earth gone bad maybe? Either on the head unit itself or the antenna.
Did you use an adapter for the antenna plug into the back of the unit?

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I did have an adaptor but now I'm using a GME whip antenna so no adaptor need now.

[Turtle_au]

Could be static from the allternator. Is there a high frequency whining sound that changes with engine revs? Also worse when the alternator output is higher ie. charging
Static can either come through the power, earth or airborne to the antenna.
If you have a portable radio see if it is affected, that will test if it is antenna issue or not.
I remember years ago you used to get suppressor capacitors that fitted to the alternator output terminal.

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[mudski]

I did notice it changed with the revs. Yeah i remember those suppressors too. But they were fitted to the ignition coil from memory...

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[Turtle_au]

I did notice it changed with the revs. Yeah i remember those suppressors too. But they were fitted to the ignition coil from memory...

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Used to fit them to both. Especially on old minis. They never worried about suppression because they never came out with radios.

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[dom14]

Even though it looks like cold engine, rev related, probably it has more to do with weak connection the antenna, power or the antenna/radio itself.
Radio antenna line ideally should have a noise filtering on itself.

[Hodge]

Believe it or not Mark. Mine is identical! Exact same symptoms.
It done it with factory aerial .
Then i completely cut it out and disconnected it and installed a Gme whip antenna like yours and issue is still present.

However mine only does it when motor is running. Motor off brings perfect radio reception.

But i never listen to radio anyway so i just ignored it.

Edit: mine is a pioneer head unit.

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[dom14]

Believe it or not Mark. Mine is identical! Exact same symptoms.
It done it with factory aerial .
Then i completely cut it out and disconnected it and installed a Gme whip antenna like yours and issue is still present.

However mine only does it when motor is running. Motor off brings perfect radio reception.

But i never listen to radio anyway so i just ignored it.

Edit: mine is a pioneer head unit.

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That clearly indicates noise interference from the ignition system.