Two types of 2 transistor 7MHz radio
I will show you two types of 7MHz radio. See fig1! Both types are single conversion super heterodyne. ** See fig2! Gate2 and drain of first transistor makes an oscillator. Antenna signal is injected for gate1. Therefore this transistor works as a convertor. 5MHz IF signal passes through a crystal filter made by a crystal. This simple filter is called a "poor mans filter".
Gate2 of second transistor makes a crystal oscillator. And IF is poured on the G1 of this transistor.Therefore this circuit works as a product detector. The audio beat signal between the 5MHz oscillator and the IF signal is heard. ** See fig3!
In this case the diagram is the same as upside. But only IF frequency was changed for 2MHz. Convertor of this radio is the same circuit from the convertor of normal 6 transistor AM radio. Filter is also the poor mans filter. Crystal between collector and gate oscillates 2000.6 KHz beat. Therefore this circuit acts as a product detector while a IF signal came from the base. ** I could hear the domestic SSB and CW QSO of 7MHz with the dipole antenna in my house. I think these circuits are the best for the new homebrewer.
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