#Bipolar transistor rf mixer manual#

If another signal is injected into the emitter of the transistor it will vary the gain of the amplifier accordingly to the level of the signal. However, if the collector load is a tank circuit (such as one of those metal can filters), the output will also be filtered around a band corresponding to the resonant frequency of the tank. In normal applications the collector load is just a resistor, and this results in simple amplification of the base signal. I believe the mixer here is what's commonly called a 'self oscillating single bjt mixer' whose basic idea is this: The transistor is biased to act as an amplifier - the signal at the base of the transistor will appear amplified at the collector. matching diodes for a ring modulator, or being sure the components work for the frequencies in question - here AM radio range), and thereby reducing the possible points of failure. I am especially looking for a kit, to avoid getting wrong or unmatched components (e.g. If anybody knows of a kit where these stages of mixing and filtering are a little more explicit and explained in more detail I would be grateful. I was expecting that it would use some relatively simple circuit like a ring modulator to do the mixing, but it is not obvious to me how this is achieved in this circuit.

Around page 31 a little about this process is explained, but it merely states that 4 types of frequencies are available at the transistor Q7, but not why. I cannot see how it is achieved and what type of mixer is used to create the intermediate frequency. While I like the instructions, especially regarding tuning with a scope and signal generator, I find them a bit lacking regarding the mixing part.

#Bipolar transistor rf mixer manual#

But I want to take the next step and understand a heterodyne AM radio, and found an interesting kit: MODEL AM/FM-108CK SUPERHET RADIO for example here: The full instruction manual is available online. Hello, I have been experimenting with radios for a while now, starting with a crystal radio, experimenting with filters and oscillators.