Ramsey Electronics AM25, Сборка и инструкция по эксплуатации

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AM25
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4
INTRODUCTION
Many times we wish to be heard via wireless communications. Whether
transmitting music or voice, what is required is a stable transmitter tunable to
an unused frequency on the broadcast band. Here at Ramsey, we have
produced several models of FM transmitters and an entry level AM
transmitter. Recent requests for a synthesized AM type transmitter have
been answered with this kit.
The Ramsey AM25 transmitter is a true broadcast transmitter, which any
person may build and use in accordance with the rules of one’s national
telecommunications authority. For U.S. residents, that authority is the
Federal Communications Commission (FCC). The AM25’s low power
broadcasting capabilities make it practical for many uses, but one should
remember that this transmitter is definitely not a toy. We will refer to the FCC
regulations frequently in this manual and provide you with some information
necessary to enjoy the AM25’s capabilities in accordance with the law.
Typical uses for the AM25 include:
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Student operated school radio stations.
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Re-broadcasting received audio for shortwave or HAM radio use.
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Listening aid for auditoriums, churches, or other events.
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Short range experimentation.
We think that you will be very pleased with the transmitting range, audio
quality, and frequency stability of this build it yourself AM transmitter. If you
follow our assembly instructions carefully and use your AM25 in accordance
with applicable FCC rules, a whole new world of sharing news, views, and
music with friends and neighbors awaits you.
AM25 CIRCUIT DESCRIPTION
Before we dive into the circuit description of the AM transmitter, first we’ll
describe exactly what we mean when we say “AM”. An (A)amplitude (M)
modulated signal is actually a combination of two signals. The high
frequency carrier is the frequency that one will tune on the radio receiver’s
dial, from 530 to 1750 KHz. The modulation is the audio information that
rides “on top” of the high frequency carrier, resulting in a changing of the
level, or amplitude, of the output waveform. Take a glance at the schematic
and follow along at how we produce this AM waveform.
The RF oscillator consists of Q4, Q6 and associated components. The
frequency of operation is determined by selecting the proper values for L5,