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I.F. Amplifier - The I.F. transformer primary has 18 turns, the secondary winding
has 4 turns. The capacitors across the IFT primaries are 82pF. The input/output
transformer has 12 turns, tapped at 3 turns from ground. This transformer is wound on
a ferrite core. The mosfets are 3SK45's. The diodes in the product detector are
1N34's. I use a six pole SSB filter from a scrap CB. The centre frequency is 7.8MHz.
The -6db bandwidth is about 2.5KHz. (added 02/05)
IF Amplifier Circuit - Three of these amplifiers are used in series to build the
455 kHz IF amplifier. AGC voltage comes from the AGC Circuit. The diagram above shows
the circuit for the second IF amplifier. (added 02/05)
Trimless IF VCO: Part 1: Design Considerations - This application note explores
the design fundamentals needed to implement a trimless, fixed-frequency, IF
voltage-controlled oscillator (VCO) and points out the challenges in guaranteeing
proper circuit operation. VCOs are essential components in the architecture of most
wireless systems. In dual-conversion approaches, a fixed-frequency.... APP 711: Feb
05, 2001 (app note added 5/05)
Tunable IF with TDA7000 - The main motive of the mods was not that the circuit
didn't work right, but were several tries to add some kind of frequency indicator to
the receiver. The left RCA plug and associated components are witnesses to the last
version, adding a FET buffer amplifier and taking signal from the oscillator coil.
(added 02/05)