Heathkit SB-101                     back to start page


Heathkit once offered an optional frequency display for the HW and SB series of transceivers. This was the SB-650. It operated in the 3-30MHz range and calculated the receive/transmit QRG from the three internal oscillators. The frequency resolution was 100 Hz.

Today, it is very difficult to find a used, working SB-650 on hamradio markets. I therefore decided to build my own for my SB-101, which still works nicely. All technical information about the SB-650 is available, including the schematic and explanation of the circuit design. See for example here: [Link]. I replaced the old TTL - ICs with their newer and smaller SMD versions and the Nixie tubes by 7-segment LED displays. Two small PCB boards were designed as well as a shielded enclosure, fitted on the left side of the VFO. The LED display was placed behind the window for course scale. Certainly, some adaptations of the original SB-650 circuitdesign were necessary. The stabilized DC supply was derived from the heater voltage. The project was a lot of work and also a lot of fun. The SB-650 ´successor´ works very nicely. See the figures below.




The LED display fits well behind the upper window. The mechanical drive of the course scale was removed. I inserted red transparent plexiglass to improve contrast of the LED display behind.




The counter is mounted vertically next to the VFO. The three shielded cables connect the counter with the HFO, BFO and VFO. The other unit from copper-clade epoxy in the background is the DC supply.



Here is a look into the shielded housing, made by copper-clad epoxy board. The boards are single-sided. Cross-connections were made by enameled wire



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