537
Item nr.
Improved Matchbox receiver
| Production | The Netherlands, 2021. |
|---|---|
| Bands | MW. |
| Semi- conductors | TA7642 (Tuner IC), BC337 (Amplifier). |
| Cabinet | Matchbox. Size 70x55x17mm. |
| Power | Batt AAA. |
| Documents | Schema. |
This is already the sixth project I built with the TA7642 IC and I tried to learn from two earlier, similar projects. The Matchbox radio taught me that (1) the TA7642 IC alone produces a too weak sound to be really useful; (2) a button cell cannot be soldered and continues to give connection problems; and (3) a matchbox is very small, so use tiny parts.
The Pina Colada taught me that (4) adding LW isn't really useful because there are few stations and the IC doesn't perform well on LW; (5) a BC337 transistor as output amplifier works miracles for the sound level, so that even a speaker can be connected; (6) an alkaline battery can be perfertly soldered; (7) connecting the headset on the Tip and Ring (TR connection) works well for mono headpieces and for stereo headsets, where the halves are used in series automatically; and (8) receiving a lot of stations is technically satisfying, but you only really use the radio for local stations.
The back has a small tuning wheel and indications for the two local stations (D=Domstad, P=Paradijs); unfortunately, Fidelio doesn't come through and below 1000kHz the radio oscillates.
| Obtained | 3/2021 from Home made. |
|---|---|
| Condition | 8. |
| Value (est.) | 2,2€. |
It is based on the Tuner IC TA7642, but has an extra transistor BC337 to amplify the output. The Kids Radio uses inductive tuning with a home wound coil, but to allow for tiny construction I used capacitive tuning and a very small ferrite rod antenna. I found sufficient miniature capacitors and resistors, and all parts fit in the matchbox easily.
