Frequency Read-Out For Sw Receiver

EE 39 July/August 1988 FREQUENCY READ-OUT FOR SW RECEIVER Although the circuit described here was designed as a frequency read-out for a short-wave receiver, it can also be used as a universal counter. The text of this article will be described on the basis of the `SSB receiver for 20 and 80 metres" (1). The block schematic of the unit is shown in Fig. 1. The signal to be measured is first fed to a variable-gain amplifier and then applied to an up/down counter via a NAND gate. The value at which count- ing starts depends on the setting of a number of preset switches. The final count depends on the setting of the up/down switch and may be larger or smaller than the preset value. To obtain a stable read-out, a latch has been in- troduced between the counter and the LED display, which stores the outcome of the measurement. The timing section serves to ensure that the other sections operate in time and with the required ac- curacy. The block schematic of relevant sections of the recei...