Honeywell International Inc. DMA-37B2 Manuale Utente

Page 13

10 Oct 2007

DMA-37B DME System

© Honeywell International Inc. Do not copy without express permission of Honeywell.

(1) The DMA-37B DME System is an airborne distance measuring system which 

determines the slant-range distance from an aircraft to a selected ground based DME 

transponder (see Figure 3). The DMA-37B DME Interrogator transmits a pulse-pair 

signal on any one of 126 frequencies within the range of 1025 MHz to 1150 MHz. One 

hundred of the DMA-37B transmit frequencies are automatically selected by tuning the 

NAV control to a frequency between 108.00 and 117.95 MHz. The other 26 frequencies 

can be selected by tuning the NAV control to frequencies between 133.30 and 135.95 

MHz, these channels are normally used for military TACAN stations. The data loader and 

data recorder capability in Figure 3 are used in the -0101, -0202, -0303 only

(2) The signals transmitted by the airborne DMA-37B are received by the ground station 

assigned to the selected channel frequency. After a built-in delay of 50 microseconds, a 

reply pulse-pair is automatically transmitted on the channel frequency assigned to the 

ground station. There are 252 channels within the frequency band of 962 to 1213 MHz 

set aside for DME ground stations.

(3) The DMA-37B receives the response to the interrogations and processes these signals 

to determine the precise amount of time that has elapsed between transmission of a 

pulse pair and reception of the response. The DMA-37B computes the slant-range 

distance by subtracting the 50 microsecond delay and dividing the result by 12.359 

microseconds (time required for DME signal to travel to and return from a DME ground 

station that is one mile away). The distance is computed every time a pulse pair 

response is received from the ground station.

(4) An operator initiated self-test feature is also included in theDMA-37B. The self-test is 

initiated by pressing the TEST pushbutton on the front panel of the DMA-37B. There are 

one or more additional means of initiating the self test; these switches can be located on 

the DME tuning source, DME indicator, or an EFIS (electronic flight instrument system) 

indicator.

RF Conducted Emissions 
(Narrowband) 

L 

RF Radiated Emissions (Narrowband) 

L 

Lightning-Induced Transient Susceptibility, Pin Injected 

ZZZZZ 

Lightning-Induced Transient Susceptibility, Multiple Pulse (Burst) 

ZZZZZ 

Lightning-Induced Transient Susceptibility, Multiple Stroke 

ZZZZZ 

Lightning Direct Effects 

X

Icing X

ESD Susceptibility 

A 

Fire, Flammability 

C 

Table 8. Environmental Certification (066-50013-1212 only) (cont)