LKG Industries kit 80-065 varactor tuned FM transmitter

[tlu]

Hi All,

Has anyone order this kit and tried to build this FM transmitter? The kit I received has parts that are not longer supplied with the original diagram. One of these is the varactor which is replaced by a PN2222 transistor with one of it's legs cut off. The second is an MV209 which is a tunable inductor and now the kit supplies a core with wires which you have to manually wrap around with 7 turns.

I started to put this together on a breadboard instead of the supplied pcb to see if it will work or not. However I'm not getting any luck. Just asking to see if others on here have played with this kit.

[Tube_Dude]

I started to put this together on a breadboard instead of the supplied pcb to see if it will work or not. However I'm not getting any luck.

Hi

A breadboard is not ideal for very high frequency circuits ~100 MHz. Too much parasitic capacitance and inductance.

Try it in the supplied PCB, where, wishfully, every parasitic had been taken in account and your luck will change... 

[tlu]

Hi Tube Dude,

Thanks for the advice. The instructions are terrible with this kit. The tuning varactor is being made with an NPN 2222A transistor with one of its leg cut off. It is not clear with leg should be grounded in the instruction and on the supplied pcb it looks like it can go both way since the silkscreen has no indication.

Should the base of it go to ground? It looks like either the emitter is cut off according to the pin out for it on a datasheet I'd looked up.

Tim

[SeanB]

Should be reverse biased to act as varicap diode. Base to ground.

[tlu]

Thanks SeanB