(6)  
Place test oscillator on ground, approximately 15 feet away from marker beacon antenna., Extend antenna on test oscillator to its fullest extent, and place parallel to fore and aft axis of the airplane. Turn test oscillator on and allow to warm up.

(7)  
Set marker sensitivity control switch to HIGH, With carrier frequency set at 75.00 MHz, turn oscillator ON and set modulation to 400 Hz.

(8)  
Check that blue lights on captains and first officers instrument panels come on and 400-Hz tone is audible.

(9)  
Repeat steps (7) and (8) with modulation set at 1300- and 3000-Hz. Check that amber and white lights come on respectively, and tones are audible.

(10)
Repeat steps (7), (8) and (9) with marker sensitivity switch set to LOW. (Move test oscillator closer to marker antenna, if necessary.)

(11)
Remove electrical power if no longer required.

May 15/72 34-35-0 Page 501 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

MARKER BEACON ANTENNA - REMOVAL/INSTALLATION
1.  Equipment and Materials
A.  Bonding Meter (Ref 20-22-01)
2.  Remove Marker Beacon Antenna
A.  Remove screws around outer edge of antenna (Fig. 401).
B.  Lower antenna from mounting recess until antenna cable can be disconnected.
CAUTION:  DO NOT PULL ANTENNA CABLE.
C.  Disconnect antenna cable from antenna connector.
D.  Remove antenna.
3.  Install Marker Beacon Antenna (Fig. 401)
A.  Check antenna, mounting surface and airplane faying surfaces for corrosion or other foreign material and clean if necessary.
CAUTION:  BE CERTAIN FAYING SURFACES ARE CLEAN. INADEQUATE RF GROUNDING WILL CAUSE IMPROPER SYSTEM OPERATION.
B.  Apply corrosion preventative material to antenna, mounting plate and structure faying surfaces (Ref 51-21-91 CP).
C.  Connect antenna cable to antenna connector.
D.  Position antenna in recess and install mounting screws.
E.  Do a check of the electrical bond:
(1)  
Remove one antenna mounting screw.

(2)  
Position the bonding meter between the mounting screw hole and the airplane skin.

(3)  
Check the bond (Ref 20-22-01).

(4)  
Make sure the resistance does not exceed 0.1 ohm.

F.  Install the antenna mounting screw.
G.  Perform System Adjustment/Test (Ref 34-35-0).
Oct 20/91 34-35-11 Page 401 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

H24884
Marker Beacon Antenna Installation (Typical)  500 
34-35-11  Figure 401  Feb 15/68 
Page 402 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

WEATHER RADAR SYSTEM - DESCRIPTION AND OPERATION
EFFECTIVITY

Airplanes With Sperry Primus 90 Weather Radar
1.  General
A.  The weather radar system presents the pilots with a topographic map type of display of moisture laden weather formations (WX) or major terrain features such as rivers, coastlines, major mountain peaks, and cities for position fixing (MAP). The weather displays permit the pilot to avoid, if possible, storm penetration and the associated turbulence.
B.  The basic weather radar system consists of a receiver/transmitter (R/T) unit, an antenna, and an indicator control unit (Fig. 1). The control allows the crew to select various modes of weather radar operation depending upon the type of video data desired. The indicator's main function is to give a visual display of potential weather turbulence or a display of the terrain ahead of the airplane, at various ranges, as well as on either side. The receiver/transmitter generates and transmits high energy radio frequency (rf) pulses which are radiated by the antenna. A small portion of the radiated energy is reflected back to the airplane by moisture laden clouds or by major terrain features. The reflected signals are received by the same antenna, processed by the R/T unit and displayed on the indicator. The transfer of the RF energy between the R/T unit and the antenna takes place via the waveguide. Stabilization of the antenna in pitch and roll is provided by the attitude reference system.
2.  Indicator
A.  The weather radar system indicator unit is a high resolution color indicator which displays weather, operating mode, and fault information on a 5-inch CRT. The CRT uses an X-Y raster scan.
B.  The indicator control panel contains pushbutton mode selector switches, rotary TILT, GAIN, and INT control knobs, rotary RANGE and STAB selector knobs, and pushbutton AZIM, SEC SCAN, FRZ, and TGT ALRT switches (Fig. 1).
C.  The radar returns are presented in four colors. In the WX (Weather) and CYC (Cyclic) modes, the colors are: dark, no Returns; green, least Returns; yellow, medium Returns; red, maximum Returns.
　
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