AM1
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4
INTRODUCTION
Many times we wish to be heard via wireless communications. Whether
transmitting music or voice, what’s required is a stable transmitter tunable to
an unused frequency on the broadcast band. Here at Ramsey, we have
produced several models of FM wireless units for years. Recent requests for
an AM type transmitter have been answered with this kit.
The Ramsey AM1 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 AM1’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 AM1’s capabilities in accordance with the law.
Typical uses for the AM1 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 AM1 in accordance
with applicable FCC rules, a whole new world of sharing news, views, and
music with friends and neighbors awaits you.
AM1 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)mplitude (M)
odulated 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 Q6 and associated components. The
frequency of operation is determined by selecting the proper values for C9
and C10, and adjusting the inductance of coil L2. The “buffer” amplifier (Q5)
is connected to the base of Q6 in order to use the undistorted oscillator
Summary of Contents for AM1
Page 6: ...AM1 6 PARTS LAYOUT DIAGRAM...
