1. The following circuit is based on a commercial design of mine from the 1970s covering 0.8 -
The photo on the right shows an internal view of the instrument. The 200 -
The low frequency inductors are lifted above the chassis to maximise the Q.
2. DC Buffer
The circuit below uses two single op-
The power consumption is sufficiently low to permit battery operation but an on-
As shown, both op-
Low voltage op-
The overall sensitivity could be further improved by providing a small forward bias to the wavemeter OA90 diodes -
Inductor L4 is made of 18swg tinned copper wire and is divided into two parts. L4a is two wires in parallel from the wafer to the body of the 150pF tuning capacitor and L4b is a hairpin loop of the same size wire. L4b is adjusted during calibration.
Resistor R1 ensures that the sensitivity cannot be reduced to zero and is typically about 2 -
The sensitivity and selectivity can be improved a little by the use of a unity gain op-