Hi to all!

I have made this 13.8V Regulated Power Supply of mine which I used for my portable vhf transceiver so that i can get rid of using it`s battery pack when i'm at home. But this power supply produces a humming sound output for the receivers which is very annoying to hear, my fellow Ham said i should put a lot of high valued electrolytic capacitors to the output but seems nothing had happened. The transformer that i used was a 3amp. 12vac and now i am asking for your help so that i can get rid of that annoying sound when i listen to another portable radio, Did i missed something perhaps a components for the schematics or there`s another schematics for removing that hum? I guess there`s somebody which is a Ham here or knows about tansceivers please help.

Salamat,

Clint

Did you put the electrolytics between the bridge and the input of the 3-terminal regulator?

What value? Are they new? How physically big are they? Are they getting hot?
What is their working voltage?

Don't forget, the 2N3055 passes a lot of hum because it has very little separation between its input and output.
The 3-terminal regulator has about 1,000:1 The 2N3055 has about 20:1

This is somthing that no-one has ever mentioned before.

Yes i put about a 4,700uf capacitor, another friend of mine told me that there`s no way i can eliminate that annoying sound of humming but to use a 15-0-15 transformer instead of 12-0-12 but what i have is 12-0-12 and i find him seems right because i made another 12-0-12 regulated power supply using a simple regulator LM7812 but still a humming sound was heared. The thing that bothers me for not using a 15-0-15 is that i am afraid if a regulator would be damaged and that 15vac when converted to dc will become more or less 19-20vdc and therefore if will short to the damaged regulator will go directly to the transceiver which cannot hold up to 20vdc thus resulting to damaging the transceiver.

Yes you are right i just used only 2 diodes but it is quiet a bigger diode (6amps maybe) and i attached it to a heatsink too, the transceiver can manage 1 amp from a 5watts transmission. I remembered i opened a zebra Porta10 1amp and it is using a 15vac transformer but when the transceiver is transmitting a power output of 5watts, excessive heat from the transformer occurs and a loud humming too that`s why i made a 3amps regulated power supply but it was only 12vac transformer that i used. I haven`t tried using a 15-0-15 yet because i don`t have it in the first place.

That will work but it won't be very good.

The emitter follower's output will drop as the load increases, totally ruining the good regulator provided by the LM317.

See the National Semiconductor datasheet as already suggested.

Originally Posted by Hero999

That will work but it won't be very good.

The emitter follower's output will drop as the load increases, totally ruining the good regulator provided by the LM317.

See the National Semiconductor datasheet as already suggested.

Hero was right, i noticed that when my transceiver is transmitting the 5watts power, the voltage drops by almost 1 volt ++, i`m not really good in electronic theories it`s just that i made this power supply from a very simple schematics for transceivers.

@ Prash

Thanks fellow ham for explaining but as what i have said i just followed this schematics and i don`t know what was missing.

Here is the full schematics of what i have made. Please comment on this..