Transmit Operation

WARNING: MAKE SURE PERSONNEL STAY A MINIMUM OF SIX FEET AWAY FROM THE VERTICAL STABILIZER WHEN THE HF SYSTEM TRANSMITS. RF ENERGY FROM THE HF COMMUNICATION ANTENNA CAN CAUSE INJURIES TO PERSONNEL.

WARNING: DO NOT OPERATE THE HF COMMUNICATION SYSTEM WHILE FUEL IS PUT INTO THE AIRPLANE. INJURY TO PERSONS AND DAMAGE TO EQUIPMENT CAN OCCUR.

Make sure the active frequency display 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 HF radio.

Listen for transmissions on the frequency you selected. When the frequency is clear, push and release the push-to-talk for the microphone. This causes the HF coupler to tune to the transmission frequency. While the coupler tunes, the HF transceiver supplies a 1 kHz tone. You hear this tone on the speaker and in the headset.

Normally, it takes several seconds for the coupler to tune. When the 1 kHz tone stops, the HF system is ready to transmit.

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 flight interphone speaker. The flight interphone system mutes the sidetone to the speaker when you use the boom mic or the hand mic.

You can continue to transmit and receive on the frequency you selected.

When you select another frequency and key the mic to transmit, the HF coupler tunes again. You hear the 1 kHz tone while it tunes.

Non-Normal Indications

If you hear the 1 kHz tone for more than 15 seconds when the coupler tunes, there may be a coupler fault.

If the tone only lasts as long as you key the microphone, you may have tuned a frequency which is outside the frequency range for the HF transceiver.

Training information point - bite Radio Communication Panel bite Indication

When you push the HF switch on the radio communication panel (RCP), the display usually shows an HF radio frequency. The range of HF radio frequencies is 2.000 MHz to 29.999 MHz.

If the built-in test equipment in the RCP senses a failure, you see one of these displays:

• INOP INOP

• FAIL FAIL

• PANEL FAIL

If the built-in test equipment in the RCP senses a failure, you

see FAIL in the active display and the standby display is blank.

If the RCP receives no signal from the HF transceiver, both displays show frequency. This occurs when one of these conditions is true:

• There is no HF transceiver

• The HF transceiver has no power

• The HF transceiver can not send ARINC 429 data to the RCP

• The RCP does not receive the ARINC 429 data from the HF transceiver

• Wiring from the HF transceiver to the RCP is bad.

If the RCP receives the FAIL WARN signal from the HF

transceiver, the display shows FAIL in both displays. This

occurs when the BITE in the HF transceiver senses that the

transceiver has a failure.

If the RCP has a failure, the display shows PANEL in the active display and FAIL in the standby display.

Hf Transceiver bite Indication

Lights on the front of the HF transceiver only show BITE results when you push the transceiver front panel TEST switch. The lights show these failures:

• LRU STATUS

• KEY INTERLOCK

• CONTROL FAIL.

The LRU STATUS light comes on red if the HF transceiver has a

failure. These are examples of failures of the HF transceiver:

• The voltage from the power supply is low

• The microprocessor has a failure

• The frequency synthesizer is not locked-on

• The output power of the RF transmitter is low.

The KEY INTERLOCK light comes on red if the HF coupler has a

failure. These are examples of failures of the HF coupler:

• The voltage from the power supply is low

• The microprocessor has a failure

• The frequency synthesizer is not locked-on

• The output power of the RF transmitter is low.

The KEY INTERLOCK light comes on when you key the

transceiver and the key interlock signal from the coupler is

open.

The HF antenna coupler opens the key interlock signal if one of

these conditions occurs:

• The other HF radio transmits at the same time

• The power supply in the HF antenna coupler is not good

• The tuning reactance is not in tolerance

• The time to tune the HF antenna coupler is too long.

The CONTROL FAIL light comes on when the HF transceiver

does not receive a signal from the radio communication panel.

This occurs when one of these conditions is true:

• The RCP is off

• The RCP has no power