Merry Christmas & Happy New Year 2009
I'd like to take this time to wish all of you a very Merry Christmas.
This is a season of giving, peace, understanding and goodwill among all. I hope that this Christmas will find you among friends and family with good food, good times, and good memories. And I hope too that Santa lines the bottom of your Christmas tree with all the Amateur Radio goodies that it can hold!
Wish you a very happy new year, many nice DX contacts, a lot of pleasure with our hobby and see You in 2009 again!
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Power supply for amateur radio |
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Transceivers with an output around 5W (CB transceivers, VHF handhelds, QRP rigs) are needing around 1,5A DC current and 13,8V voltage. Favourite ICs 7812 have an internal current limitation on 1A. That's the reason why are they used only like reference stabilisator in bigger power supplies.
Power supply with special ICs like LM723 are unnecessarilly comlicated. PSU with Zener diode like reference voltage are not very favourite. Many constructors are forgotting on stabilisators with 1.5 or 3A currents.
It looks like many others PSUs, where is the difference? There is a transformer, rectifier, capacitor and stabilisator.
The difference is in the IC. Like has been sayed, 7812 stabilisator is a good solution till 1A current. In the same TO-220 package is available 78S12 (S – strong) which could handle up to 1.5A. 78H12 (H – high) could handle up to 3A current.
It's a basic circuit that can be modified. Modifications are depending on your component resources. So it's possible to use classical tranformer and Graetz type rectifier. Capacitor C1 must have at least 2.2mF for each Ampere. Capacitor C3 is covering a gaps on the on the output. Capacitors C2 and C4 are used to prevent oscillation of stabilisator. To obtain 13,8V at the output are used two silicon diodes. It's a one way how to change stabilisator voltage.
Part list:
| C1 |
2200uF or more/25V |
| C2, C4 |
100nF |
| C3 |
10uF/16V |
| D1, D2 |
1N5401 or similar |
| D3, D4 |
silicon diodes, any type |
| IO |
7812, 78S12, 78H12 |
| TR |
2x14V/1-3A |
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