Do-it-yourself bug bug
I urgently needed to assemble a listening device with my own hands. Google got wool. There were quite interesting things, from the synopsis of the series "Invisible" to "a hundred ways to hack a VKontakte account."
It turned out to be not so simple to solve my problem, although one original recipe was found. On the radio amateur website, I found a transmitter circuit with a decent range of up to 300 m. However, to establish this circuit, you need some experience.

Details:
VT1 - any transistor type KT315 (KT3102). Choose depending on the required microphone sensitivity.
VT2, VT3 - KT368 (Gain - at least 100). It is advisable to use in a metal case.
M1 - microphone type "pine", FEM-3 or some imported.
L1 - 3 turns with a 0.5 mm wire on a 5 mm frame.
L2 - 2 turns with a 0.5 mm wire on a 5 mm frame.
L3 - 8 turns with 0.25 mm wire on a 5 mm frame.
After assembly, it is advisable to place the entire circuit in a metal case.
Sweating over the "bug", I still got my way and learned a lot, a lot of interesting things. But that's another story.
It turned out to be not so simple to solve my problem, although one original recipe was found. On the radio amateur website, I found a transmitter circuit with a decent range of up to 300 m. However, to establish this circuit, you need some experience.

Details:
VT1 - any transistor type KT315 (KT3102). Choose depending on the required microphone sensitivity.
VT2, VT3 - KT368 (Gain - at least 100). It is advisable to use in a metal case.
M1 - microphone type "pine", FEM-3 or some imported.
L1 - 3 turns with a 0.5 mm wire on a 5 mm frame.
L2 - 2 turns with a 0.5 mm wire on a 5 mm frame.
L3 - 8 turns with 0.25 mm wire on a 5 mm frame.
After assembly, it is advisable to place the entire circuit in a metal case.
Sweating over the "bug", I still got my way and learned a lot, a lot of interesting things. But that's another story.