RADIO HABANA CUBA
ULTRA-SIMPLE TRANSMITTER

Dxers Unlimited for 12 June, 1999
with Arnie Coro, radio amateur CO2KK


Circuit 
Diagram The 
Ultra-Simple Transmitter is palm-sized
Wire Wrapping 
Frequency Table

Single IC 74HC240 Transmitter Parts List

C1 and C2 are mica or ceramic.

L1 and L2 are air-wound from #14 wire, with an inner diameter of 3/8 inch. You use a BIC Ballpoint Pen as the coil form (then after winding the coil, just remove the coil form, and you have an "air wound coil" that looks nice)!

RESISTORS:   Standard carbon type, they may be 20 percent tolerance. If they are better tolerance, like 10 percent or 5 percent, it's OK too.

 R1 22K ohms  0.5 w
 R2 330K ohms 0.5 w
 R3 470 ohms  0.5 w
 R4 47K ohms  0.5 w

CAPACITORS:   The 0.1 mfd capacitors should be DISK CERAMIC for better RF response but epoxy types will work, too.

 C3 0.1 mf  50 volts or more
 C4 0.1 mf  50 volts or more
 C5 22 pf ceramic, or better yet, mica or silver mica
 C6 47 pf ceramic, or better yet, mica or silver mica
 C7 20 pf Variable
 C8 47 pf ceramic, or better yet, mica or silver mica
 C9 0.1 mf  50 volts or more

0.1 mfd capacitors can be epoxy type used for bypass.

You may use smaller resistors, but the half-watt type are easier to handle and solder, especially if you are just starting in learning how to assemble electronic circuits.

The IC dissipates a lot of heat when running from an 8 volt DC source, so you MUST glue it to the printed circuit board, in order to use the copper foil as a heat sink.

You can see how this is done in the picture of the fully assembled rig above.


Questions? Send e-mail to Arnie Coro
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