Replacing Electret Microphone With Audio Input?

I've got a 10K audio taper pot. Will that also work.

It doesn't matter to me . . . Seriously: If you anticipate using it frequently to adjust volume you might be happier with an audio taper pot. If you set it once and forget about it, it hardly matters.

The question is how constant is the volume from the 'pod? If you think the control on your receiver is good enough to compensate use a linear.

It doesn't matter one way or the other - it just "feels" right when you use an audio pot for audio signals. I put a linear pot into a stereo I built at my office/shop where I was working. It had 50 W a channel and was too much for the little office but everyone who used the control said it "didn't have enough volume." Never bothered me though.

It will

OK. I hope to get this transmitter up and running today. I will post here with the results.

Built it and rebuilt it and it didn't work. I installed the 12 pF instead of the trimmer cap, even took it apart and resoldered all connections. Any suggestions why it doesn't work?

What method did you use to build it? It is a 100 MHZ circuit so layout can be critical -

The next question would be what is the transistor doing? What is the voltage from base to ground? What is the voltage from ground to the emitter? (and if it were oscillating, taking a reading there would stop it).

Can you / have you measured current consumption of the circuit?

What steps have you taken to verify it isn't working and what steps have you taken to fix it other than checking your connections?

Two things come to mind assuming no mistakes in the construction.

I would disconnect everything west of the vertical 10K that joins with the base of the transistor - it isn't necessary for oscillation.

Then I would replace the transistor with another type - I've always had better results with the metal can version of the 2N2222 for FM mics but change the transistor if you have another NPN good for high frequency.

The other thing, assuming no oscillation, is the feedback cap. It shouldn't be very critical but it can go a long way to getting a transistor that won't oscillate to start. Too high and it won't work and too low and it won't work . . .

Try a gimmick cap in there. If you have some wire wrap wire or cat 5 USTP those are probably ideal but any solid wire will work. Magnet wire is another good choice. Vinyl insulation isn't ideal at that freq so if you can get it to work with vinyl, change it for a lower loss dielectric to get maximum range.

Two wires twisted together, but not connected, form a "gimmick" cap.

No magic formula for value of the cap - thinner insulation = greater capacity, longer gimmick = greater capacity, dielectric constant of the insulation determines capacity also, dissipation factor of the insulation = Q (quality).

good insulations - Teflon, polyethylene, Tefzel, Delrin, enamel (low dissipation factor)

Without modulation - it can be hard to hear the transmitter. It will sound like a Thump when you tune through it on the receiver and it should be able to kill the sound of a weak FM station when it is tuned to the same freq.. On an analog TV with antenna, it will look like wavy lines or a herringbone pattern.