This circuit was found in an ancient American documentation. With it is possible to double the frequency of a transmitter For the range of 6 meters obtaining 8 W. The circuit makes use of varicap.
This circuit was found in a 2005 Linear Technology documentation. The circuit is based on LTC4213...
This filter has the components calculated for the frequency of 1 kHz but can be changed. The input...
This circuit works only with carbon microphones, due its low impedance. The speaker should be good or...