524
Item nr.
Small AM bug with FM receiver and Bluetooth.
| Production | The Netherlands, 2020.
Price was 14 €. |
|---|---|
| Bands | MW (999-1620kHz). |
| Semi- conductors | 2x 9018 (osc), D882 (modulator), D882 (power), CD7368 (audio), LED. |
| Cabinet | Wood cigar box. Size 12x13x5cm. |
| Power | 6V DC. |
| Documents | Schema. |
The AM mini transmitter is a construction kit obtained from AliExpress. From previous projects, I had some Bluetooth/FM/MP3 units left over, and I combined one with the transmitter in a wood cigar box. I used one that has output amplifiers on the board, but these are unused now.
| Obtained | 9/2020 from home built. |
|---|---|
| Condition | 8. |
| Value (est.) | 10€. |
| Sound sample | PLAY SOUND With the unit tuned to 1 MHz as precisely as possible, the harmonics provide me with clear signals at each MegaHertz multiple. You hear the 2nd harmonic at 2MHz from the Erres KY6531. |
The construction kit came without a thumb wheel for tuning, so construction had to wait until a jar of peanut butter was emptied. Putting the parts of the transmitter together was quite straight forward. The transmitter can be tuned roughly from 1000 to 1620 kHz. 
As can be seen from the scope image, the wave form is far from perfect, so the transmitter produces a lot of harmonics. The third harmonic is pretty strong in the Tropical bands, which is very handy for testing tropical radio's, and actually the transmitter sounds better there (by lack of disturbing signals). Even the fifth harmonic can be heard, in the shortwave bands. On the back are jacks for power (6V DC, plus is center), FM receiving antenna, and AM transmitter antenna and ground. With a ground, the transmitter works better.
