UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Chinese 1A2 Super Regenerative FM radio kit

Philips210 · 26th Dec 2018, 11:16 pm

Hi.

I've been assembling the 1A2 radio kit and something that I noticed is there's an error in the PCB copper foil pattern. This concerns the tuning capacitor. The required capacitance swing is 10 to 20pF but with the supplied PCB, and the tuning cap as connected, gives 20 to 40pF, so would tune below normal Band 2 frequencies. A cut is made to the copper foil on the central connections and a link is applied on the other end of the tuning cap (see attached pics). So in summary, the required connections to the tuning cap are to the end connections only, the central connections being isolated.

I decided to mount the aerial coupling and tuning coils on the solder side of the board as there's lack of space on the component side unless they're mounted higher off the board. As this is a VHF circuit, short lengths of any connections are preferable so a good reason to mount the coils close to the board. As a consequence of mounting the coils on the solder side, the tuning cap is also mounted on the solder side otherwise the tuning cap knob will foul the coils.

I used a few 0.1" 2-way connectors for the LT and HT battery supplies and the aerial connection. I hope to try out the circuit in the coming days.

Regards
Symon.

26th Dec 2018, 11:16 pm	#68
Philips210 Nonode Join Date: May 2007 Location: Redruth, Cornwall, UK. Posts: 2,573	Re: Chinese 1A2 Super Regenerative FM radio kit Hi. I've been assembling the 1A2 radio kit and something that I noticed is there's an error in the PCB copper foil pattern. This concerns the tuning capacitor. The required capacitance swing is 10 to 20pF but with the supplied PCB, and the tuning cap as connected, gives 20 to 40pF, so would tune below normal Band 2 frequencies. A cut is made to the copper foil on the central connections and a link is applied on the other end of the tuning cap (see attached pics). So in summary, the required connections to the tuning cap are to the end connections only, the central connections being isolated. I decided to mount the aerial coupling and tuning coils on the solder side of the board as there's lack of space on the component side unless they're mounted higher off the board. As this is a VHF circuit, short lengths of any connections are preferable so a good reason to mount the coils close to the board. As a consequence of mounting the coils on the solder side, the tuning cap is also mounted on the solder side otherwise the tuning cap knob will foul the coils. I used a few 0.1" 2-way connectors for the LT and HT battery supplies and the aerial connection. I hope to try out the circuit in the coming days. Regards Symon. Attached Thumbnails