Ramsey Electronics AR2 Manuál s instrukcemi stáhnout pdf (Strana 6)

ABM1 • 6

Audio Amplifier

The Audio amplifier section consists of R11, the On/Off/Volume control. This

part turns the power on or off and adjusts the audio level sent to the head-

phones. C20 couples the audio signal to the Audio Amplifier, U4, while isolat-

ing DC. C21 keeps high frequencies out of the amplifier. C22 is a bypass ca-

pacitor. C23 sets the gain of the amplifier to approximately 200. C24 filters

the power supply. C25 is the output coupling cap. C26 and R12 are used to

prevent the amplifier from oscillating. L2 acts as a low impedance for audio

allowing it to pass to J1 and on to the headphones.

118-136 MHz, WHAT YOU CAN EXPECT TO HEAR

A basic fact about the VHF Aviation Band which even licensed pilots can over-

look or forget is that communications are in the AM mode, not FM, as in the

case of the FM broadcast band immediately below it, and the VHF public ser-

vice and Ham bands immediately above it.

No matter where you live you will be able to receive at least the airborne side

of many air traffic communications. You'll hear any aircraft you can see, PLUS

planes up to ten miles away and more, since VHF signals travel "line of sight."

An airliner at 35,000 feet altitude is still line of sight to your antenna. Similarly,

whatever ground stations you may hear are also determined by this "line of

sight" character of VHF communication. If there are no major obstacles be-

tween your antenna and an airport (tall buildings, hills, etc.), you'll be able to

hear both sides of many kinds of aviation communication. Be prepared for

them to be fast and to the point and for the same airplane to move to several

different frequencies in the span of a few minutes! Here's a brief listing of the

most common types of services in the NAS (National Airspace System) with

which pilots communicate:

Clearance Delivery

At most metropolitan airports, a pilot communicates with the FAA on a fre-

quency called "Clearance Delivery" to obtain approval or clearance of the in-

tended flight plan. This communication is done before contacting ground con-

trol for taxi instructions.

Ground Control

From the control tower, ground movements on ramps and taxiways are han-

dled on the “Ground Control” frequency.

Control Tower

Runway and in-flight maneuvers near the airport usually within three miles

(takeoffs, local traffic patterns, final approaches and landings) are on the

“Control Tower” frequency.

ATIS – Automated Terminal Information System

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Ramsey Electronics AR2 Manuál s instrukcemi Strana 6