Bendix
Avionics
Division
ADF-T12C/D AUTO^IATIC
DIRECTION FINDER SYSTEM
Installation
Manual
2-5.A.
Sense antenna and lead-in capacitance must be within the limits of 125±25pf. Low
capacitance coaxial line should be used to minimize capacitive effects and provide
p r o p e r si g n a l le v e l s to t h e r e c e i v e r.
(8)
On installations using two sense antennas in close proximity of one another, inter¬
action between the antennas may result. The interaction may cause double reversal
of needle when flying to and over astation. To minimize this interaction mount the
antennas as far from one another as possible and in some cases make one antenna
2 f e e t s h o r t e r t h a n t h e o t h e r .
(9)
2-5.B. LOOP ANTENNA
(1)
Determine whether the loop antenna will be top or bottom mounted. Refer to the sys¬
tem interconnect diagram for correct antenna connector wiring for top mount.
(2) Select the approximate mounting location on the fore-and-aft centerline of the aircraft.
- N O T E -
Quadrantal error compensation must be done by trial and error
before the exact mounting location can be determined. Aircraft
must be well clear of any metal hangars, electric or telephone
wires, buried cables, etc. that could cause bearing errors.
Temporarily tape the loop to the outside of the aircraft. Loop must be upside down for
connector clearance and the aircraft positioned to anormal flight attitude. Make loop
cable entrance into the aircraft without drilling any holes in the aircraft skin (via
window, door, or removable inspection cover). Ensure adequate loop cable length for
the selected location.
(3)
- N O T E -
Bearing indications on the servo amplifier/indicator will be reversed with
the loop mounted upside down. Compute bearing differences accordingly.
Use aground compass rose if available. If not, the aircraft directional gyro or compass
must be used to determine aircraft rotation angles. If the compass must be used,
compass error should be checked prior to proceeding.
(4)
Select aradio station of known position, at least 20-miles distance and free from
static and fading. Tune the receiver to the station. (See paragraph 2, 7. B. (1) remark
on 2OIF tuning.)
(5)
(6)
Rotate the aircraft so that the nose is pointing directly at the transmitting station.
The servo amplifier/indicator must now read zero.
Set the directional gyro to zero degrees (or note the compass heading) and in agree¬
ment with the servo amplifier/indicator.
(V)
(8) R o t a t e t h e ai r c r a f t c o u n t e r c l o c k w i s e a r o u n d th e c o m p a s s ros e in 15 ° i n c r e m e n t s . Co m ¬
pare the directional gyro or corrected compass heading with the servo amplifier/indi-
ca t o r re a d i n g s at ea c h in c re m e n t. C h ar t t h e r e s u l t s . T h e d i f f e r en c e be t w ee n t he t w o
readings is the quadrantal error. Maximum errors will be at the 45-, 135-, 225-, and
315-degree points.
I.B. 2012-1
2-5
Revised Oct/72
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