On idle radio cuts out,new alt. bought didn't fix prob.

wow old and still on the road that old, rare here, USA.
the charge lamp means the Aternator is failing
causes are.
1: belt slips to it or belt missing
2: wire to it fell off. or burned, cut etc.
3: fuse huge 50amp blown under hood.
4:the alternator is bad.
5:engine trouble such that RPM is 500 rpm AT IDLE AND THE ALTERNATORS JUST DO NO LIKE THAT.

ALL YOUR STATED EVIDENCE IS 100% NORMAL FOR DEAD ALT.

charge up the battery and drive to a shop and tell them to fix the ALT.
they even test it.

Don't raise the idle speed, because that will adversely affect the engagement of reverse and drive and cause the car to creep forward at stop lights. Most likely there is a shorted diode in the alternator rectifier. If you can find a rectifier at a parts supplier, it is not difficult to install. Otherwise, you will have to replace the alternator.

What happened is your battery was disconnected. You need to go back and get them to fix radio and ac. Yes this is normal for radio not to work. Depending on how they checked alternator

belt worn, loose or idler pulley weak --compressor clutch binding,moisture in system ,compressor internal damage

The idle is controlled by the engine's computer and you do not solve the problem by trying to increase the engine speed - which you cant without changing computer settings.
There is a fault that needs to be identified that is causing too low an idle speed when the AC is operating if that is what you are describing. You need to have the vehicle checked by a dealer to see what fault codes it is throwing and identify what the issue is.

There is no cheapy quick fix solution.

If you gassed the ac system your self then it mat be overfull and that is why it is not working and if you did no check for leaks (why else would need gas) then it may be all pumped out . The AC compressor takes a lot of power to drive and all cars loose around 300rpm's when it cuts in so if you have an idle too low then it will drop below needed idle rpm's . Most cars have a compensating unit the raises the idle rpm when the ac is working so check out your system for a faulty unit there.

possibly could you spark plug wires or distributor faulting you will need a mechanic or a manual to adjust the distributor or just get new spark plug wires

maybe something shorting out drawing power did u have alt tested before switching out to make sure it was bad- sum auto stores such as auto zone/advanced auto can do a load test on vehicle for free will show if their is an excess draw on elect or if new alt is faulty (does happen) check serpentine belt and pulleys belt may be slipping then check ground strap , starter for draw or some other accessory

alternator needs good battery to keep SCR in the regulator on if it is loaded it will shut down. this will happen when you try rolling window down or rear defog will load up the system. When the truck is running and battery is hooked up the vehicle should run at @700 RPM at idle and when A/C compressor is commended on it should idle up to @1000 RPM and then back down to @700 RPM when compressor cycle off again. But if the system almost stalls then the battery and alternator should be changed together, A bad battery will damage a new alternator and a bad alternator will damage a new battery.

The idle system has gone bad in your car. Did anyone work on the AC? An overcharged ac also put so much load on the engine that it can make it stall when idling. The idle sytem is suppose to raise up the idle of the engine when there is a load such as a headlight or an ac system.