Ramsey Electronics AR2 Manual de Instruções descarregar pdf (Página 4)

ABM1 • 4

INTRODUCTION

Everyone from aviation enthusiasts to armchair listeners to schoolchildren

can enjoy listening to aircraft and airport signals with the ABM1. It’s an Air-

craft receiver that does not radiate RF signals so you can take it to the airport

and even onboard aircraft without worrying about causing interference. In or-

der for the receiver to be non-interfering, no local oscillators or mixers are

used. The unit directly converts the entire Aircraft Band meaning that the

user can hear all local aircraft traffic at once. Stronger RF signals will pro-

duce a louder audio signal than weaker signals, making it easy for the user to

pick out a specific conversation to listen to. This also has the advantage of

allowing the user to hear both sides of a conversation without re-tuning the

receiver. In fact, you never tune the ABM1, making it perfect for beginners

and kids learning the fun of both electronics and aviation. We think you’re go-

ing to find the Airband Monitor kit a useful and educational receiver that you’ll

be enjoying for years to come.

CIRCUIT DESCRIPTION

We’ll take the circuit in bite size chunks and explore each section to see how

the kit works. Follow along on the schematic if you wish; we’ll work from input

to output.

Antenna Input/Audio Output

Jack J1 allows the connection of a standard 3.5mm headphone jack to the

ABM1. The headphones will provide two functions. Obviously they provide

the audio for the user to listen to the aircraft band. The headphone wires are

also used as an antenna for the ABM1. L2 is a high impedance to Radio

Frequencies (RF) keeping the RF from traveling back to the Audio Amplifier.

Band-pass Filter

C1 is a coupling capacitor that allows the RF signal picked up by the head-

phone wires to pass into the 1

Band-pass filter. This filter is made up of M1,

C2, L3, C3, M2, and C4. M1 and M2 are micro-strip inductors that are actu-

ally formed from traces on the circuit board. This filter is designed to pass

only frequencies between 118 MHz and 136 MHz, the aircraft band.

RF Amplifier

The purpose of this stage is to increase the signal strength of the previously

filtered signal. C5 is another coupling capacitor; it takes the 118 to 136 MHz

RF signal from the 1

Band-pass filter and allows it to move to the RF Ampli-

fier while isolating DC. U1 is a Monolithic Amplifier that provides about 18 dB

of gain for our signal. Its frequency range is from DC to 1 GHz. Since com-

ponent leads and foil runs can act as antennas at high frequencies C6 is

used to prevent high frequency signals from entering U1 directly from the air.

R1 sets the bias for the amplifier while C7 and C9 filter the power supply.

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Ramsey Electronics AR2 Manual de Instruções Página 4