circuits enclosed are for experimental purposes only. They are not
intended for illegal use. When you apply their use in an illegal
application you subject yourself to a shitpot - and world of shit if
you are caught. Please check the Local, State and Federal laws
including the FCC rules and regulations to determine what you can and
Component Sizes: The artwork is drawn for 1/4 watt resistors. Keep the
resistors and capacitors to 5%. 1% are expensive and 10/20% components are
useless. 5% will keep the circuits and each part within its working
range. Any size components can be used - just bend the leads to fit the holes.
small capacitors are of the ceramic type 2.5 MM. The electrolytic are marked
with a + and are 2.5 MM in size. The adjustable ones are TZ03 5.1 MM Trimmers. If the holes don't line
up on the boards for whatever size you are using, just bend the leads to
fit. Use Low Voltage Types.
Surface Mount: Althought
virtually all of the artwork is TTH ( Thru The Hole ) boards in these
circuits, For years I have used the same TTH artwork for surface mount.
Here is how I do it. I simply reduce the size of the solder side of the
board to 1/2 or smaller until a standard surface mount resistor will
connect between two of the holes on one of the resistor slots.
Generally everything else will fit. I then solder the SMD parts
directly to the solder side of the board.
Stripboard Layouts: You can use
regular perfboard that has no solder side ( Holes Only ). Simply use
the "Screen Layout" supplied, push the components through and solder
the leads to each other.
Microphone Element: Any small electret element.
RF Coils: All
rf coils in these circuits are between 3/16 to 1/4" in diameter of
between 3 to 6 turns using standard magnet wire between 18 to 23 AWG.
The determining factor of what frequency the transmitter will operate
at is based on the parallel combination of the coil ( Usually called
L1, etc. ) and the capacitor in whats called the tank circuit. As a
general rule, the more turns, the lower the frequency - and the less
turns the higher the frequency. All coils are airwound using a drill
bit of 3/16" or 1/4." Generally the coil is a fixed amount of turns and
the capacitor is adjustable. If the capacitor in the tank circuit is a
fixed one - just spread or compress the turns and it has the same
the circuits enclosed are specific in the transistors they specify, it
has been my experience that most any quality NPN - VHF transistor will
work in these small transmitters. That is based on experience. The
factor that really determines if they work or not is usually the
feedback capacitor that is connected from the emitter to the collector
of the rf section - usually between 3 to 10 PF. That capacitor causes
instability in the transistor and causes it to oscillate so if you
don't use the specific transistor the circuit requires, try going lower
or higher on that particular capacitor to get the transistor to
Fleeting Thoughts: Having
specilized in the generation and transmission of radio frequency energy
over the past 60 years, I can pretty well look at a circuit and tell if
it is going to work or not. From what I see in the circuits I have
picked for this website, they all work. If your circuit does not work
it is usually the result of a wrong component, bad component or a part
in the wrong place, or an improper feedback capacitor from the base to
the emitter of the final rf. All of the circuits listed have a link
enclosed that will
direct you to the original website where the circuit has been posted
for all of the circuit specifics and details so go there - rather than email me for any details.
I put a great deal of time building this site based on hundreds of emails from folks that found me on my regular website Bugplan.Com looking
for these types of simple transmitter circuits. I did the work and it
is presented in these pages. If you need Professional Circuits, please click into the Blue Link ( Bugplan.Com ) directly above this line.
(C) 2012 By Radio-Circuits.com