This step of two transistors has a high input impedance due to the use of FET. We can use BF245 for this function and the bipolar can be BC548. The circuit is from an 1975 American documentation.
This circuit was obtained in a magazine for radio amateurs 73 of the 90s. The circuit is based on...
This circuit is from a documentation on the MC1539 from Motorola and may, however, be implemented...