4 Transistor-5 IC SW Receiver

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This is a 4 transistor-5 IC dual-conversion superheterodyne receiver with continuous coverage of the Short Wave bands from 5.7 to 18.1 MHz. The receiver demodulates AM broadcast signals only, and has the following features: 2 FET RF amplifiers in the front end for high sensitivity with a short wire or telescopic antenna, 2 Gilbert-cell balanced mixers/oscillators for clean signal conversion, 2 IF amplifiers with an efficient AGC stage good handling of strong signals, a sharp 6-stage IF filter for high adjacent channel selectivity, a smooth 8:1 vernier dial for easy tuning, and a red LED next to the tuning knob for indicating relative signal strength. The receiver runs on 12 volts DC and performs as good as or better than portable shortwave receivers on the market.

Receiver schematic


Dimensions: 7"(L) X 5"(D) X 3"(H). Controls from right: Tuning, antenna gain, volume and power on/off. Power LED and audio jack are above and below on/off switch respectively. A smooth 8:1 vernier dial provides easy tuning in the crowded bands at night. Red LED left of vernier indicates relative signal strength. Black banana jack on top accepts a plug-in telescoping antenna, which is more than enough for this sensitive receiver to monitor the world.


Receiver back: 12 Volts DC power supply cable connects to the RCA jack at right. In case the telescopic antenna is not available, a short wire antenna can be connected via the red compression terminal at left. A ground wire can also be connected via the black compression terminal to improve reception.


Inside the receiver: The first RF amplifier was originally designed with a tuned circuit, so the receiver required a 3-gang variable capacitor (left). Unfortunately, receiver performance suffered from tracking problems, forcing me to use an untuned first RF amp., and leaving an unused section in tuning capacitor. The full circuit was built "Manhattan style" on one 4 1/8" x 4 1/2" single-sided ccb (copper-clad board). 3/16" dia. ccb islands were glued at strategic places on the board and used to connect and hold the components. The board's copper surface served as a common ground and boosted stability. 455 Khz IF filter (black block, center right) was assembled from six ceramic filters glued together and wired in series. Although not as selective as mechanical filters I have used in other receivers, the filter provides excellent selectivity, at a much lower cost. ICs pluged in sockets, while all other semiconductors and passive components were soldered directly to the board.


Signals from the antenna are controlled with a potentiometer and fed to the first RF amplifier, which isolates the antenna from the RF tuned circuit. A second RF amplifier channels the selected signal to a Gilbert-cell mixer/oscillator, where it is down-converted to a 1st IF of 10.7 Mhz. A crystal filter after this mixer passes the converted signal and eliminates the image frequencies. The 10.7 Mhz signal is amplified by the first IF stage, and down-converted again by a second crystal-controlled Gilbert-cell mixer/oscillator to a 2nd IF of 455 Khz. This signal is passed through six ceramic IF filters connected in series which provide high adjacent channel selectivity. A second IF stage amplifies the signal before it is demodulated (detected), filtered and sent to the AF amplifier. A sample from the second IF amplifier is detected and amplified by the AGC stage which controls the gain of both IF amplifiers to keep volume at a relatively constant level. A red LED connected to the output of the AGC amplifier indicates relative signal strength.

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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