This project is relatively simple to construct, and will give a "presentable" SSB signal on the lower HF amateur bands. Above 14MHz frequency stability may become a little annoying to the listener due to this TX being VFO controlled, but with a little care, and attention to 2nd oscillator component temperature and mechanical stability, operation on 18MHz should be possible.
The circuit is divided into three sections:
SSB EXCITER
This unit generates an SSB signal at an IF of 455KHz. TR1 forms the carrier oscillator which feeds the mixer and crystal filter. The oscillator coil uses an IF transformer from one of those cheap'n-nasty AM radio's. The filter uses two 455KHz crystals that have a difference frequency of about 1 - 1.5KHz. You will find that the cheaper crystals are never on the same frequency, and they may be "selected" to find a pair with the required difference. To select the crystals temporarily use them instead of L1 in the carrier oscillator circuit and monitor the frequency of oscillation. You can monitor the oscillator on a 160 meter receiver (4th harmonic, 1.820MHz) and look for crystals that give a 4-6 KHz difference in beat-note. Alternatively you could use an SSB crystal filter in the place of the two crystals. The 455KHz oscillator is tuned to one side or the other of the crystal filter passband and is sufficiently stable to maintain this frequency offset. When monitoring transmission set the carrier oscillator so that the carrier cannot be heard or is at a very low level. The capacitor "C" is an integral part of the 455KHz IF transformer used for L1.
T1 and T3 are constructed using 1/4" ferrite rings. T1: Twist together three lengths of thin enamelled wire and wind 18 turns on the ferrite ring. The tap of the secondary is the START of
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