Reception Set R 308 (by Jim Cookson, G4XWD)
The R308 VHF communications receiver has a family resemblance to the R 107, R 206 and R109 receivers and the WS53 transmitter. It shares a similar case to the R 107 and is just as heavy at 112 lbs.
It will operate from AC mains of 100 to 250 volts or from its own built in 12 volt vibrator PSU. A panel mounted octal plug is used to change over supplies.
Frequency coverage is 20Mc/s to 145 Mc/s in 5 bands clearly calibrated in Mc/s, with a beautifully smooth two speed dial drive, and operating modes of FM, CW and AM.
A double conversion superhet design with a 1st IF of 9.72 Mc/s and second of 2.1Mc/s is used. Incidentally there is a monster foreign station on 9.72 these days which can cause IF breakthrough. I realigned mine on to the universal 10.7Mc/s IF, assuming that there must be an international convention to keep that frequency clear.
14 valves, mostly octal, are used but with EF54s in the front end and a VR92 diode first mixer. The aerial input circuit with its trimmer is designed for dipole operation and has screw terminals on the front panel.
Three selectivity positions, 20kc/s, 60kc/s and 140kc/s, all at –6dB and labelled narrow, medium and wide, are provided.
Sensitivity is listed as 2 – 5 microvolts on FM, and 3 microvolts on AM, which, compared to the results mine gives seems ambitious. I would compare its performance to that of the Hallicrafters S27.
It is a very handsome set and pleasant to use, with built in speaker and headphone storage behind a small door in the front panel.
© G4XWD