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.
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.
IF-Amplifier for PMR 446 Purposes:
Low Distortion IF Amplifier/ADC Driver with
Digitally Controlled Gain: Linear Technology
Single and Dual-ranch IF Amphifier
Matching Circuit: WJ
Communications May 2003
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
amplifiera and taking signal from the oscillator
Ultralow Distortion IF Amplifier/ADC
Driver with Digitally Controlled Gain:
Linear Technology LT5514
VHF/FM Transistor Radios: