Schematic & Wiring Diagram

Microphone Pre-Amplifier 9-12Volt Discrete

This is a microphone pre-amplifier ambit that use detached components. The accretion of this ambit is 100 and should be abundant for best microphones. It is set by the arrangement of the 10k resistor to the 100R. As common-emitter amplifiers, This ambit uses two anon accompanying transistors. Here is the schematic diagram of circuit:

Please agenda that this ambit has no bent voltage source, so you can’t use with condenser blazon microphones. You can use this ambit with activating blazon microphone, or condenser electret bore with alive ambit central (any microphone which is able with array central can be used).

Multi-Band AM DSB Transmitter Circuit Shcematic

The ambit of AM transmitter is advised to address (amplitude modulated) DSB (double ancillary band) signals. A articulate AM arresting consists of a carrier and two symetrically spaced ancillary bands. The two ancillary bands accept the aforementioned amplitude and backpack the aforementioned information. In fact, the carrier itself coveys or carries no information. In a 100% articulate AM arresting 2/3 rd of the ability is ashen in the carrier and alone 1/6th of the ability is independent in anniversary ancillary band.

In this transmitter we abolish the carrier and transmitt alone the two ancillary bands. The able achievement of the ambit is three times that of an agnate AM transmitter.

Op Amp IC741 is acclimated actuality as a microphone amplifier to amplify the articulation best up by the condenser microphone. The achievement of the op amp is fed to the bifold counterbalanced modulator (DBM) body about four IN4148 diodes. The accentuation akin can be adapted with the advice of preset VR1.

The carrier is generated application clear oscillator active about BC548 transistor T2. The carrier is added amplified by transistor T1, which additionally acts as a absorber amid carrier oscillator and the counterbalanced modulator. The alive abundance of the transmitter can be afflicted by application crystals of altered frequencies. For multi abundance operation, alternative of altered crystals can be fabricated application a selector switch.

Ths achievement of the DBM contains alone the artefact (of audio and carrier) frequencies. The DBM suppresses both the ascribe signals and produces bifold ancillary bandage suppressed carrier (DSBSC) at its output. However, back the diodes acclimated in the counterbalanced modulator are not absolutely matched, the achievement of the DBM does accommodate some balance carrier. This is accepted as carrier leakage. By adjusting the 100 ohm preset VR2 and trimmer C7 you can absent the carrier leakage.

To accept DSB signals you charge a exhausted abundance oscillator to reinsert the missing carrier. If you don't accept a exhausted abundance oscillator, or appetite to transmitt alone AM signal, acclimatize preset VR2 to aperture some carrier so that you can accept the signals on any accustomed radio receiver. In AM approach 100% accentuation can be accomplished by adjusting preset VR1 and VR2.

The DSBSC arresting accessible at the achievement of the counterbalanced modulator is amplified by two stages of RF beeline amplifiers. Transistor 2N2222A (T3) is acclimated as an RF pre amplifier, which provides abundant arresting addition to drive the final ability amplifier body about transistor SL100B. The achievement of the final ability amplifier is affiliated to the antenna.

All coils are to be anguish ferrite balun amount (same as acclimated in TV balun agent of admeasurement 1.4 cm * 0.6 cm) application 24 swg enameled chestnut wire. Proper calefaction bore should be provided for SL100B transistor acclimated as final ability amplifier.