single oscillator single chanal ssb tranceiver
with some cheap standard X-tals one can build a ladder filter.
one oscillator with the same frequency X-tal operates as local and beat frequency oscillator simultanly.
two mixers (ne602/ne 612) make the conversion from HF to IF and from IF to AF .
RX and TX signal goes the same way. the bandpassfilter to select the operating frequency can be wide, because the mirror frequency is null (DC).
the bandpass must suppress the IF.
i found no other cheap X-tals that could target another HAM band bandplan conform, but 10 m is wide and 28.636 MHz should be OK for this kind of experiments.
the 28.636 MHz signal comes from the antenna through the low pass and the bandpass filter to the first mixer were it is converted to 14.318 MHz IF (the half of the HF frequency).
the IF signal pass the ladder filter (witch should be about 3 KHz wide to be able to clarify).
eventually a AGC driven IF amp follows the ladder filter
before the signal is converted to audio frequency by the second mixer.
than a audio amp follows.
TX:
a one stage mic amp feed the first mixer.
the oscillator frequency mixed with the TX audio result in a DSB signal.
the ladder filter selects the upper side band.
than the IF is mixed with the local oscillator signal and the result is 28.636 MHz.
than the SSB signal passes the bandpass filter and is amplified in the linear amp.
the low pass filter cuts off harmonics and the signal is transmitted by the antenna.
its just a brain project. but what is it good for ?
1.
when use it in a local net with strong partner stations, the RX can be simple.
2.
to be able to DX with low power (QRP) the RX should be sensitive. 28.636 than should be known by everyone as a QRP frequency.
3.
make a stand alone packet radio (pactor) transceiver and setup a local net with your friends.