Datel ETX1 is a simple 80m transmitter with class E power amplifier. The output
power depends on the supply voltage and is about 5W for 12V. The efficiency can
be more than 80% and is a benefit of this PA. Changing output LC circuits the
transmitter is capable to work on 1.8, 7 or 10MHz band. For external VFO signal
disconnect jumpers JP5 and JP6, the minimum input voltage is approx. 2Vpp. Gate
IC2A can be used as an oscillator too. In this case connect jumpers JP5 and JP6.
On JP4 is then signal for counter or RX mixer. The alignment of output circuit is
quit hard, but it allows obtain more than 60dB suppression of all unwanted harmonics
without degradation of the efficiency. With capacitance trimmer C19 tune the 2nd
harmonic suppression, with C12 maximum of the 1st harmonic and C6 rejection of the
3rd harmonic. To avoid efficiency decreasing use good low loss capacitors for at least
50V and rated torodial core. For 7Mhz and above, air coil for L2 is recommended.