This General Electric circuit is from the 80's. The PUTs used in this meter are not common components today.
The sensor in this circuit is a BA315 diode. Other diodes can be experimented, but this is one...
We found this circuit in a Radio Experimenter Handbook from the 90s. The circuit uses 741 op amps...
This circuit is from a magazine 73 for radio amateurs of the 90s. The circuit generates the high...