I am a newbie to building and testing rf mixers. I just finished building my first homebrew mixer and I need to test it. Thanks for sharing your experience with homebrew mixers. Dear OM, two tone is modulated to test and evaluate mixer performance only. Otherwise RF signal is modulated only with an audio signal from the microphone. See XENA project on this blog for details.
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I am a newbie to building and testing rf mixers. I just finished building my first homebrew mixer and I need to test it. Thanks for sharing your experience with homebrew mixers. Dear OM, two tone is modulated to test and evaluate mixer performance only. Otherwise RF signal is modulated only with an audio signal from the microphone. See XENA project on this blog for details. An integrated circuit IC , is a semiconductor wafer on which thousands or millions of tiny resistors, capacitors, and transistors are fabricated.
An IC can function as an amplifier, oscillator, timer, counter, computer memory, or microprocessor. A particular IC is categorized as either linear analog or digital, depending on its intended application. Linear ICs have continuously variable output theoretically capable of attaining an infinite number of states that depends on the input signal level.
As the term implies, the output signal level is a linear function of the input signal level. Analog or linear ICs invaded amateur designs in early seventies and were favored for cost and compatibility. There were numerous designs using them as mixers, IF amplifiers and AF amplifiers among others to say. Mixer ICs became popular for their ease of implementation in compact designs with predictable performance. Most of these devises are obsolete and out of production.
You have to shell a considerable wad of bucks to get one. These devices are primarily developed for broadcast band radios and TVs, and are equally difficult to find in local markets. Thus; the non-availability of these items led me to look out for cheap alternative……. Sounds impossible; but here is how I make them. They produce almost the similar results in simple receivers.
The one I love to play with is legendary CA, a single ended differential mixer. This IC is the most versatile device with a protean set of possibilities to go with.
It can be used as a mixer, differential amplifier, a cascade amplifier with AGC, a balanced modulator, product detector or even a frequency multiplier.
You can Google to download a detailed data sheet of this device. The entire circuit can be wired as the above diagram using the component values mentioned. Beyond that any transistor with higher gain bandwidth product as BFR90 are quite suitable. The Q1 and Q2 should be matched units. You can use any of the following jigs to match transistors.
Give a resting period of few seconds for both transistors to be matched and do not touch them. The touch of finger can alter alter the junction temperature of the transistors and thus causing confusing results. The final home brewed mixer on the DIP socket this way can be used in any design as a standard IC circuit. It does not cost an arm and a leg and is far cheaper and easier alternative.
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CA3028A Amplifiers. Datasheet pdf. Equivalent
November Controlled Constant Current Source. VHF Ranges. Ordering Information. Schematic Diagram. Terminal Numbers Apply to All Packages. Users should follow proper IC Handling Procedures.
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