Saab 340B, Руководство по эксплуатации

Страница: 249 / 670

COMMUNICATIONS, HF COM
Operation
Aircraft Operations Manual
4/2.2
O
PAGE 7
Apr 01/15
COLLINS HF 230
CONDITIONS NORMAL PROCEDURES
(Cont’d)
3. Squelch control SET . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
− Start with the control at TST and turn clockwise until background noise
is barely audible.
− Do not rotate squelch control too fast. Squelch circuit has a relatively
long time constant and rotating knob knob too far may result in missed
calls on some of the weaker signals.
− Setting the squelch control too far clockwise can result in blocking out
weak signals. The operator will find that there are times (depending on
prevailing conditions) when it will be necessary to maintain satisfactory
reception. This is because of conditions relating to propagation and the
ionosphere that causes the HF receiver to have to operate with a signal
that is subject to considerable fading and which is only marginally
strong (unlike the conventional VHF which normally operates with a
strong line
− of − sight, nonfading signal).
4. HF volume lever READJUST . . . . . . . . . . . . . . . . . . . . . . . . . . . .
− If necessary, compensate squelch by increased volume.
− Always be prepared to meet fading by increased volume.
Transmit
1. XMIT SELECT HF pushbutton SELECT . . . . . . . . . . . . . . . . . . . .
− Check to be illuminating.
2. PTT button PRESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
HF transmission disturbs the ADF system.
CAUTION
The HF must be returned each time changing to new channel or frequency, be-
fore transmitting.
NOTE