The Amplifier RF Deck

This is the circuit diagram of the RF deck. This is all pretty traditional with little surprise.

Note 1: C2 consists of a feed-through capacitor and a 500pf, 7.5kv button capacitor placed next to the anode choke.

Note 2: VC3 was very nearly fully engaged when tuned and I couldn't compress the coil, so I added a 7.5kv 1000pf capacitor in parallel.

Click on the component to see a photograph

The DXpedition Amplifier RF Deck Circuit Diagram

The DXpedition Amplifier RF Deck

Parts List

RF Deck
Supplier      Part     Number     QTY   


Cathode side
Maplin RFC3   LB12N 1 3/8" ferrite rod (for filament choke core)
14-turns, bifilar-wound,16swg insulated, close wound
College RFC2   1 85mm length of 20mm PTFE rod
50-turns 22swg on tufnol or PTFE rod
  TC1 C804 1 100pf Jackson panel mounting variable capacitor (input tuning) or equiv.
  L1-L2   2 10-turns, 18swg, 20mm diameter, spaced 1-turn
RS C1   1 4,700pf mica
Anode side
Surplus VC1   1 3-30pF vacuum variable (Jennings or Comet)
Surplus VC2 CAV-250F20 1 250pF, 2kV Johnson variable capacitor or equiv.
College L3   1 18" 6mm pure copper tube (do not use car brake pipe)
3-turns, wide spaced, 32mm dia (silvered)
College RFC1     85mm length of 20mm PTFE rod
50-turns, 22swg, close wound
  RFC4     85mm length of 5mm PTFE rod
approx 60-turns 22swg, close wound
      1 Eimac 8877 valve
Surplus   (TUA)SK2200   1 Johnson ceramic 8877 base
Surplus   (TUA)C8877 1 8877 teflon Chimney
RadioDan    CX-800N 1 Dual N-type coaxial relay
College     1 12" length 1/2" 18-guage brass strip to connect 8877 anode to anode choke and C3 (silvered)
RF Parts C2a 580500-7 1 500pf 7.5kV doorknob
Linear Amp UK C2b   1 750pf feed-through capacitor
RF Parts C3   1 1000pf 20kv doorknob
RF Parts   HV-20   3ft 20swg 30kV HT cable