Two-crystal filter for SSB
The filter for the formation of the SSB signal can be collected with just three quartz on the same frequency. Two quartz are used in the filter, and the third - in reference generator. A schematic diagram of a two-crystal filter shown in Fig. 1.
The frequency of one of quartz, designed for installation in a filter it is necessary to increase at 2 kHz, then the frequency band passed by the filter will be about 2.5 kHz. Ways of increasing the frequency described in the article Zvereva "crystal filter for SSB" ("Radio", 1966, No. 7).
To check the spacing of the frequencies of the oscillators should be collected auxiliary generator according to the scheme shown in Fig. 2. The difference frequency is determined by connecting to the output of the oscillator frequency, or (in extreme cases) at the hearing the pitch of the beats phones. Coil filter L1 and L2 is wound in two wires. Mid-point of the coil is formed by connecting the one end of the wound wire with the beginning of another.
In the two-crystal filter, collected by the author were applied to quartz frequency 6,333 MHz. The frequency of one of quartz was increased to 2 kHz. Coils L1 and L2 were placed on the frame of the inverter circuit of TV set "Record" and contained to 13 coils which are wound two wires PELSHO 0,1 simultaneously. The filter is installed in the transmitter of the radio station UA3QAV.
Assessment of correspondents (including collective radio UA3RDO owned by the magazine "Radio") quality SSB signal radio UA3QA good.
Author: S. Gubar, Voronezh; Publication: N. Bolshakov, rf.atnn.ru