This reflectometer or standing-wave ratio meter (SWR) was found in a 1980s American documentation. The diodes support general purpose equivalents.
The integrated circuit 4136 consists of operational amplifiers of type 741 in the same enclosure and...
In the figure we have an active high pass filter of 100 Hz, suggested by National Semiconductor in its 1994...
According to the consulted American publication of the 1980s, a zener diode can be used for DC...