Microphone and Headphone Jacks

Microphone (mic) and headphone (phone) jacks give

connection points for mic and phone use.

 

 

General Description

The VHF antenna receives and transmits RF signals in the VHF frequency range.

The antenna attaches with 10 screws. There is an aerodynamic smoother around the antenna base. This aerodynamic smoother is a sealant. An o-ring seals the coaxial connector. NOTE: For the top antenna, the cable can fall through the hole. Уплотнитель гермет - ки закрывать

When you remove the top antenna, make sure you

attach the cable to something to prevent this.

 

Receive Operation

The VHF antenna receives RF signals and sends them to the VHF communication transceiver through the coaxial cable. The transceiver sends the RF signal through the receive circuits and then sends the audio to the flight interphone system.

The transceiver also sends data to the selective calling

(SELCAL) decoder.

 

The VHF 3 transceiver sends data to the aircraft communications addressing and reporting system (ACARS) management unit.

The microprocessor sends the receive frequency to the

frequency synthesizer. The frequency synthesizer sets the

frequency of the AM receiver.

The microprocessor also sends a logic 1 to the transfer switch when the transceiver is in the receive mode. This closes the transfer switch and sends the RF signal from the antenna to the AM receiver.

The AM receiver demodulates the RF input and detects the audio signal. The audio output from the AM receiver goes to these circuits:

· Data output circuits

· Switch S1

· Squelch comparator.

 

The audio output circuits send the audio signal to the flight interphone system and to the headphone jack.

Do a test of the receive audio circuits with the TEST push button. Push the TEST push button to close switch S1 and send the receive audio to the audio output circuits. This lets the operator hear background noise not normally heard.                                    порог

The squelch comparator circuit compares the detected audio with a threshold value. If the level of the detected audio is larger than the threshold, the squelch circuits sends a ground to switch S1. Switch S1 closes and sends the audio to the audio output circuits.

For the VHF 3 transceiver, the microprocessor changes the audio off signal to a logic 1 when the transceiver is in the data mode. This causes switch S1 to open and disable the audio output and the squelch comparator.

 

Transmit Operation

The VHF tranceiver receives audio from the remote electronics unit (REU). The transceiver sends the signals through the transmit circuits and then to the antenna for transmission.

During transmission, the microprocessor receives a push-totalk (PTT) signal from the REU. This causes the microprocessor to send a logic 0 to the transfer switch. The transfer switch connects the output of the transmit circuits to the VHF antenna. Mic audio from the REU goes to the transmit circuits in the transceiver. The transmit circuits modulate the RF carrier with the mic audio. This makes an amplitude modulated RF signal. The signal goes to the directional coupler and transfer switch.

The RF signal goes through the transfer switch and to the

antenna. The antenna transmits the RF signal.

The RF output from the directional coupler also goes to the power monitor. The power monitor sends a logic 1 when the output power is larger than 15 watts.

The side tone switch closes when the output power is larger than 15 watts and the transceiver is in the voice mode. The microphone audio goes through the REU to the flight interphone speakers.

 

For the VHF 3 transceiver, the microprocessor changes the audio off signal to a logic 1 when the transceiver is in the data mode. This sends a logic 0 to the sidetone switch and turns off the sidetone audio.

 

 

General

You use these components to operate the VHF radio:

· Microphone or headset

· Control wheel mic switch

· Radio communication panel (RCP)

· Remote mic switch

· Audio control panel.

 

Receive Operation

 

You use the radio communication panel and the audio control panel to receive transmissions on the VHF radio.

On the audio control panel, push the receiver volume control for the VHF radio. Turn the control to adjust the volume from the VHF radio.

You hear audio on the headset and the flight interphone speakers. To hear sound from the flight interphone speakers, push the speaker (SPKR) volume control to turn on the speaker. Turn the control to adjust the volume of sound from the speaker.                                       В начале

When you apply power to the airplane, the radio communication panels (RCPs) are on. Initially, RCP 1 tunes VHF 1 and RCP 2 tunes VHF 2. Push the VHF microphone selector switch for the VHF radio you want to use. A light above the switch comes on to show which radio the panel controls. When you push the audio control panel microphone selector switch, the VHF receiver volume control is automatically selected. The frequency indicators show VHF radio frequencies. The VHF transceiver tunes to the frequency in the active frequency indicator.

Use the frequency selectors to tune the radio to a new

frequency. The standby frequency display shows the new

frequency.

 

When you are sure the frequency is correct, push the frequency transfer switch. The active frequency indicator shows the new frequency. The VHF radio uses the new frequency.

Listen to the audio from the VHF radio on the speaker or

headset. Adjust the volume control switches on the audio

control panel for a comfortable sound level.

 

Transmit Operation

 

Make sure the active frequency indicator shows the frequency you want to transmit. Make sure the frequency you select is a valid transmit frequency.

Push the microphone selector switch on the audio control panel for the VHF radio.

Listen for transmissions on the frequency you selected. When the frequency is clear and you want to transmit a message, key the mic and speak into it. You hear sidetone in the headphone and muted sidetone from the speaker. The flight interphone system mutes the sidetone to the speaker when you use the boom mic or the hand mic.        Приглушать звук

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