1. A PRACTICAL PROJECT FOR FAREHAM & DISTRICT AMATEUR RADIO SOCIETY
QRP POWER METER
A PRACTICAL PROJECT FOR FAREHAM & DISTRICT AMATEUR RADIO SOCIETY

2. THE CIRCUIT

3. COMPONENTS Diode: 1N914 / 1N4148 or BAT85 (Schottky)
Resistor: 50R Carbon, 1/2 W
Capacitor: 1nF 30v Ceramic
Meter: Any low current f.s.d. small meter
(50 / 100 micro Amp)
Socket: BNC for aerial / input
2 banana skts. for ext. meter connection
Switch: 1 pole c/o
Misc.: Double-sided pcb approx. 35mm. X 75mm

4. WHAT YOU'LL NEED Soldering Iron (small bit, 25W min)
Solder (Multicore)
Small Drill / Bits
Reamer
Forceps / pliers
Hot Melt Glue or other fixing means for meter
Island cutter

5. LAYOUT

6. POWER CALCULATIONS
Power (W)= V2/R (normally)
But Gizmo reads Peak Power
Therefore (here) P=V2/2R Watts
And allowing for the voltage drop across the diode,
P (W) = ( V + diode v. drop)2 / 2R
===========================