YO4HFU
DDS HF TRANSCEIVER SSB/CW

 

This SSB/CW transceiver is designed to cover 160m-10m amateur bands. VU3CNS DDS with AD9850/1 was used with satisfactory performances. Some spurious can be found above 14MHz band. DDS clock signal (150MHz) is an external oscillator to minimize the phase noise. The internal PLL of AD9851 is disabled. LCD module and DDS board were necessary to be shielded.
The RX has a single intermediate frequency (IF 9MHz). The SSB filter is an old Unitra crystal filter. One more filter can be inserted for CW narrow mode. The topology of RX chain is similar with Kenwood TS series. The internal 2N5109 is useful for higher bands. An "MFJ" audio filter (HPF/LPF/BPF/Notch) helps the operator. Is a good receiver and has a low noise figure due FI MOS-FET stages and diode DSB detector.
Elecraft K2 band pass filter are used for rx/tx. I chose these filters because can be easily adjusted. DL7MAJ made some modifications of Elecraft K2 filters, check the download section. All relays are controlled by VU3CNS uController.
Output power is around 10W from pair 2N3375 transistors. Better transistors are recommended for 12V operation. An audio limiter/compressor was installed on audio tx.

DOWNLOAD
HF DDS SSB/CW Schematic Diagram
AD9851 DDS modified
Other informations about DDS: Link VU3CNS DDS.
Audio Filter CW/SSB MFJ-722
Band Pass Filter Elecraft K2 modified by DL7MAJ
Improved ALC circuit with LM3900


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