100W AM Transmitter using N2488 circuit diagram schematic



Published
See previous video for main schematic without the power amplifier at https://youtu.be/XFEQK2ERZpM

Unit combines the 10W transmitter (see previous video) with a 100W RF power amp. The power amp uses two N2488 Darlington audio transistors which are relatively easy to salvage from discarded stereo equipment. These transistors are not ideal for the AM band frequencies, but they are free and quite rugged. The ferrite toroids are also salvaged from discarded power supplies and re-wound to obtain the 1mH primary inductance. The power amp section runs on 20V @ 1A. The pair of N2488 transistors are biased via a 7805 regulator with a potentiometer to adjust the bias current. The 10W main transmitter section (see previous video) runs on 12V @ 250mA via a 7812 voltage regulator. A 100W / 50 ohm RF resistor is used as a test load and signal attenuation.
Several high value decoupling capacitors as well as current limiting resistors and an NTC surge protector are added to isolate the power supply and protect the circuit. A small fan keeps the unit cool.
This video is for educational purposes only. A shortened antenna and 50 ohm test load attenuate transmission to within allowed limits.

Music in this video
Song
Who Am I - Live
Artist
Casting Crowns
Writers
Mark Hall
Licensed to YouTube by
SME (on behalf of Reunion Records); SOLAR Music Rights Management, LatinAutor - SonyATV, LatinAutorPerf, CMRRA, BMI - Broadcast Music Inc., LatinAutor - UMPG, Essential Music Publishing, Adorando Brazil, PEDL, UNIAO BRASILEIRA DE EDITORAS DE MUSICA - UBEM, and 12 Music Rights Societies
Category
Audio
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