|If you're planing
to power your transmitter from batteries, than you can skip this section!
You might want to read it to get an idea.
You will need a good
12 volt, 2 (Minimum) - 8 (Future expansion) Ampere Regulated Power
Supply. No "wall wart" please! Short circuit protection
is useful, but not mandatory. Adjustable output voltage gives you
additional feature, you will be able to change your transmitters
output power by changing voltage of your power supply. Not bad.
You can sometimes squeeze more power out of your transmitter if
you raise voltage over rated voltage for your transmitter. But be
careful, this is likely to destroy your output transistor, blow
some capacitors or cause excessive heating. Importance of proper
power supply is often underestimated. Poor power supply can cause
several problems, add hum to your signal, cause interference to
your neighbors (typical for AM systems where RF leaks into power
lines), too low output power, unstable operation etc. Radio Shack
is a good place to look for cheap stuff, as well as ham stores and
If you prefer to
build your equipment by yourself, get your soldering irons and check
out these projects:
This is a simple
"variable output" power supply. Now, left of this circuit
would be standard line voltage transformer (110-220/18V) and a standard
gretz rectifier with smoothing caps (10000uF or even better more).
The heatsink of the 317 regulator must be isolated from the ground
If you need
a stronger power supply, check:
This is a pretty
strait-forward circuit. You might need to bypass C5 with a bigger
capacitor (10-100uF). Diode D makes up for the BE loss of 0.7V of
the 2N3055 transistor. If you need higher voltage, use 7815 instead
of 7812 and connect pin 3 directly to ground. This will give you
14-14.3V on the output. I built several power supplies like that
for my CB/ham stations and they work very well. Of course you have
to add mains transformer and rectifier bridge + smoothing caps,
just like above. Caps should be as big as possible (20000uF or more).
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