DDS Modified Johnson VF-122 VFO. Great VFO module. To safely operate with a tube transmitter, you need to ensure that key line voltages are isolated from the sensitive processor pin (23, Key). This pin has a 5vdc pullup. Grounding it keys the VFO. If you connect a transmitters key line direct the higher voltage can destroy the DDS chip! The D-lab Opto-key module solves this issue. I have been informed that most operators, free run the VFO, shift the VFO frequency while in receive so not to interfere with the receiver. Some have tried using relays for keying, but that introduces clicks on CW mode. So I set out to design a fast response keying & isolation circuit. Works great. Hook-up is simple. Small easy to interface. Other designs are in the works. Example Heathkit (DX-60) plus other popular models. If your interested, let me know. Right now only the Johnson Viking II model is tested, ready.
15 апр 2024
