Tuesday, February 14, 2012

A single-transistor 16 dB gain RF amplifier

Here are two photos of an RF amplifier built by KE4ID using the popular bug construction. (Click on each image to enlarge.) The use of a readily-available metal box saves cost and provides a convenient ground plane to which components can be directly soldered for grounding and mechanical support. The circuit is based partly on designs published by KK7B in QST and in the ARRL book Experimental Methods in RF Design.

Jack loaned this amplifier to me for evaluation as an interface between a stand-alone Yaesu digital VFO and my Heathkit SB-104A transceiver. I'm in the process of breadboarding a similar unit for this function. The output of the Yaesu VFO needs to be boosted to 3 V p-p to match what the Heathkit internal VFO provides. An existing jack for an external VFO makes the connection to the Heathkit convenient. The goal is to obtain a more stable and precise frequency control than what is possible with the internal analog VFO.

Here is the schematic diagram.(Click to enlarge.)

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