6 Transistor-7 IC SW Receiver

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The drifting analog VFO is history!

This is a 6 transistor-7 IC dual-conversion superheterodyne receiver with continuous coverage of the SW bands from 5.7 to 22 MHz. It has a DDS VFO (Direct Digital Synthesis Variable Frequency Oscillator) and a back-lit LCD frequency display for accurate and drift-free tuning. The receiver copies AM broadcasts and SSB (Single Sideband) Radio Amateur signals and has the following features: an IC (Integrated Circuit) RF amplifier for good sensitivity with a short wire antenna, 2 Gilbert-cell balanced mixers for clean frequency conversion, AM and SSB mechanical filters for superior adjacent channel selectivity, 2 IF amplifiers with AGC (Automatic Gain Control) for good strong signal handling, a crystal-controlled BFO (Beat Frequency Oscillator) for stable reception of SSB signals, a tunable AF (Audio Frequency) filter that eliminates interference between stations, and a signal LED to show relative signal strength. The receiver runs on 12 volts DC and performance is on par with high quality commercial SW receivers.

Receiver schematic


Dimensions: 12"(L) X 7"(D) X 3"(H). Controls from left: Top row: Volume, AF Filter, LCD frequency display, Memory Call, RF Tune and RF Gain. Bottom row: USB/LSB, SSB Mode, Memory Down, Tuning, Memory Up, Slow AGC, 2.5K/5.8K Filters and Power On/Off. Speaker jack is to the left of volume control. Signal strength LED is below AF filter control. Memory push-buttons are used to adjust functions of the DDS VFO such as IF shift and Tuning step. In SSB mode (HAM/Radio Amateur communications), Slow AGC and 2.5K filter are switched on. USB/LSB switch selects the BFO crystal. AF filter control tunes the AF filter between 0.9 and 10 Khz to eliminate splatter from interfearing stations.



Receiver back: Ground and Antenna wires connect to the black and red spring terminals. Antenna Off push-button disconnects the antenna so I can peak the RF tuner by ear for maximum static. 12 volts DC supply connects to the red RCA jack.



Inside the receiver. Circuitry was built Manhattan style on 2 large copper boards attached together. Copper surface was used as a common ground to improve stability. All ICs (Integrated Circuits) plug into IC sockets. DDS VFO is green board at center. RF tuning capacitor is bottom left. AF filter tuning capacitor is bottom right. AM and SSB IF filters are green rectangular components at center left. BFO with USB and LSB crystals are upper right. LCD display was attached to the case with aluminum standoffs and modified terminal strips.


A short history | My radio background | Homemade radios | Tube radios
Transistor radios | World band radios | Kit radios | Reel tape recorders
My other interests | Pictures of Lebanon | Radio links
Home | Showcase | About this site

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