3 Transistor - 1 IC SSB Monitor

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Cq Dx, Cq Dx, Cq Dx, this is W1BF beaming to South Australia over the long-path and standing by... HAMS (Radio Amateurs) have been on the air ever since radio was invented. I am not a HAM myself, but I enjoy listening to HAM stations with a mug of coffee in hand. Here is the first of two SSB Monitors I built to use with my homebrew receivers to listen to SSB (Single Sideband) Communications. This monitor demodulates SSB and AM signals and has the following features: An analog BFO (Beat Frequency Oscillator) which stabilzes in less than 5 minutes, an active differential BJT (Bipolar Junction Transistor) product detector with good strong signal handling, a voltage doubling diode AM detector for coppying regular broadcasts, and a low distortion IC (Integrated Circuit) AF amplifier with volume control for comfortable listening with headphones or a speaker. The monitor runs on 12 Volts DC which supplied by the receiver.

Monitor schematic


Dimensions: 5"(L) X 4"(D) X 2"(H). Controls from left: Volume, AM/SSB, Power on/off and USB/LSB. Power indicator LED is left of volume control. Phones/Speaker jack is below LED. The USB/LSB control (capacitor) tunes the BFO (Beat Frequency Oscillator) inside the monitor to slightly above (LSB) or slightly below (USB) 455 kHz. Switching to AM allows the monitor to demodulate regular broadcasts.



Monitor back. A 3-wire cable plugs into 3-pin jacks on the monitor and receiver to supply the monitor with the required IF (Intermediate Frequency) signal and 12 volts DC.



Inside the monitor. Circuit was built Manhattan style on 2 copper boards. Black Murata filters are lower center. BFO (Beat Frequency Oscillator) on the left uses a common yellow core IFT (Intermediate frequency transformer) and is adjusted for USB & LSB modes with an air variable capacitor (lower far left). Differential product detector is in the center. AF amplifier IC plugs into an 8-pin sockect at right. AM detector is on top. Volume control is on lower right.


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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