The purchased equipment was either fairly expensive or rather old. It's possible that the move towards digital services in the UK is to blame but we weren't able to find any cheap transistor radios that had a BFO.

We then looked for a kit that contestants could build. The three main contenders were

• the KRC5 from the Kit Radio Company (KRC) at £25.99
• the Knapp from Walford Electronics at £22 without case
• the VEC-1180K Vectronics 80m Receiver Kit from Vectronics at £29.95 (plus £14.95 for the case).

The kits all use a direct conversion design. Walford uses discrete transistors but the others use two integrated circuits (SA602 and LM386)

We spoke to club members who had built kits from KRC and Walford Electronics. (We couldn't find anyone who had built a Vectronics radio kit although many had successfully built other Vectronics kits). They confirmed our suspicion that the radios were rather deaf. This is probably because the SA602 provides 18dB of gain and the LM386 provides 46dB. A further 20dB of voltage gain is provided by the aerial input circuit. The total gain is therefore 84dB. Thus a 1 microvolt signal at the aerial will provide only 16mV at the speaker, which is still microwatts!

There were plenty of direct conversion designs available on the Internet as well. Many of these were also based on the SA602/LM386 pair. We built a couple of these to test them and although they worked reasonable well they were as deaf as the Walford/KRC designs.

In addition, none of these kits had a directional aerial.

Therefore, we decided to design our own rig