User manual

and the higher the reception frequency. The only tuning point is coil L1 to set the

lower threshold of the oscillator frequency. The low frequency end stage is a

simple class-A ampliﬁer with the two transistors T1 and T2. Quiescent current is

approx. 20 mA. The circuit still works at a good sound as of an operating voltage

of 2.2 V.

The PCB is designed so that all components are equipped in SMD build around

the actual receiver TDA7088. This makes set-up easy. Some of the wired compo-

nents soldered in by you can be replaced to change certain radio features. R1 de-

termines the frequency range that can be tuned. A smaller resistor increases the

tuning range. This is a good idea, e.g. if you want to operate the radio with NiMH

batteries at 2.4 V. R2 determines the width of the AFC capture range. If you want

to be able to listen to, e.g., weak stations close to stronger stations, it may be a

good idea to increase R2 up to MO to reduce the capture range. The two connec-

tions RE2 and SC1 on the PCB are initially not used. They are reserved for later

expansions. The TDA7088 was originally developed for button tuning. The two

buttons for „reset“ and „scan“ are included in the circuit diagram. If you want to

convert the receiver accordingly, the PT2_2 connection to the frequency con-

troller slider must be separated. You can install a switch here, so that the re-

ceiver can be tuned either by buttons or the poti. For more information on

possible conversion, see the online magazine ELO (www.elo-web.de).