R1,R2,R3 = 51 ohm 2 watt non inductive. R4 = 1K ohm 2 watt. RV1 = 10K ohm linear control or pre-set control. D1 = OA91 type diode. C1 = 0.001 uF ceramic disc. C2 = 0.01 uF ceramic disc. S1 = 4-pole 3-way switch ( Maplins) Meter = 1Ma or less. 2 SO239 antenna sockets. Suitable metal box or case.