TKM MX385 User manual

INSTRUCTION MANUAL

FOR

MX385 NAV/COMM TRANSCEIVER

11/16/98 1/15/02 07/29/08

1 2 3 4 5

TKM, INC

14811 N. 73

STREET

SCOTTSDALE, AZ 85260

PART # IMN385, REV. 5

JULY 29, 2008

TABLE OF CONTENTS

TITLE PAGE 1

TABLE OF CONTENTS 2

I. INTRODUCTION 3

A. Purpose of Equipment 3

B. Equipment Description 3

C. Specifications 5

II. INSTALLATION 7

*Notice to Installer* 7

*Continued Airworthiness (HBA 98-18)* 7

III. HOW TO OPERATE 8

IV. THEORY OF OPERATION 11

V. ALIGNMENT AND TEST SPECIFICATIONS 14

VI. MECHANICAL DISASSEMBLY 16

VII. TEST PROCEDURES 17

VII. SCHEMATICS, LAYOUTS AND PART LISTS 27

MX385 Interconnect (J1) 27

MX385 Interconnect (J2) 28

IDENTURED LIST OF DRAWINGS 29

Top Assembly 31

Computer 41

Front Panel 51

Display 57

Driver 62

Rear Panel 66

Rear Panel Assembly 76

Connector Board 86

T/R Switch 89

COMM Receiver 94

COMM Synthesizer 109

Transmitter 117

NAV Receiver 130

NAV Synthesizer 143

I. INTRODUCTION

This manual contains information on the Michel MX385, manufactured by TKM, Inc.

The information includes operational, mechanical, electrical descriptions, alignment and

test considerations.

A. Purpose of Equipment

The equipment is a 760 channel communication (COMM) transceiver for use in aviation

services and a 200 channel navigation (NAV) receiver to provide VOR/LOC signals to

navigational converters. The NAV receiver also provides frequency selection for remote

mounted Distance Measuring Equipment and Glideslope Receivers.

The MX385 is designed to be used as a direct replacement for the Cessna/ARC RT385A.

The unit is dimensionally identical to the ARC units and can therefore use existing

aircraft installations. Except for improved performance characteristics, the unit is

electrically interchangeable with the ARC unit and will provide the proper audio,

navigation signal and channeling signals for existing installations. New installations can

be made using RT385A installation kits.

B. Equipment Description

The unit features digital (LED) displays for active (yellow) frequency channel and

standby (red) frequency channel for both COMM and NAV.

For channel selection a MHz knob and a KHz knob are provided. For 25 KHz

increments in COMM, a 25 KHz button is provided. To activate COMM or NAV

frequency selection, an N/C button is provided; a ‘tic’ appears in the selected standby

channel display.

Channel selection operates on the standby channel only. When the desired channel is

indicated in the standby display it may be placed into the active position by depressing

the ‘Flip-Flop’ button located to the left of the displays; the active channel is then placed

into the standby position.

The NAV receiver features a VC/ID button to permit selection of voice or Ident

reception. In the Ident condition a ‘tic’ is displayed on the active NAV channel display.

The COMM transceiver features a test button, which overrides the squelch to verify

proper receiver operation and to allow reception of weak signals. Also provided on the

active COMM display, is a ‘tic’ to indicate transmitter power output.

The master power switch is integrated with the COMM volume control.

A VOR test button (VT) is provided for testing navigational systems; depressing the

button provides a ground on the appropriate rear panel contact.

The adjustment hole (D) by the MHz switch permits operator adjustment of the display

dimmer range for optimum nighttime viewing. The adjustment hole (S) by the KHz

switch permits operator adjustment of the squelch threshold.

The MX385 is comprised of eight replaceable subassemblies; five of the subassemblies

are contained in shielded modules to reduce radio frequency interference. The five

modules are the NAV receiver, the NAV synthesizer, the COMM receiver, the COMM

synthesizer, and the Transmitter.

The remaining three subassemblies are the Rear Panel Assembly, the Front Panel

Assembly and the Computer Board. The Rear Panel Assembly contains the Audio

Amplifier, the power converter, the Power Line Filter, and the T/R switching. The Front

Panel Assembly contains the digital displays and associated driver circuits, the functional

select switches and the volume controls. The Computer Board contains the

microprocessor, the memory, the Program storage, and the Channeling circuitry.

Also contained on the computer board are the audio processing circuits.

The subassemblies are interconnected with plugs to facilitate module replacement. For

equipment repair it is recommended that complete subassemblies be replaced.

As an aid to locating the defective subassembly a set of analog test points are provided.

The analog test points include the receiver tuning voltages, the synthesizer control

voltages and the AGC lines.

C. SPECIFICATIONS

MX385 TRANSCEIVER

Mounting: Panel mounted, no shock mounting

required.

Size: 6.312 x 2.50 x 11.1 inches w/

connectors but excluding knobs.

Weight: 6.0 lbs excluding external connector

and harness.

Power Requirements: 27.5 Vdc at 0.7 Amp

Max COMM Total w/

Transmit (Tone) 3.0 Amp

COMM TRANSCEIVER

Crystal Controlled: 760 Channel

Frequency Range: 118.00 to 135.975 MHz

Frequency Stability: +/- .003%. –20 to 50 C

TRANSMITTER

VHF Power Output: 8 watts minimum, 50 ohm

Modulation: 85% capability with 90% limiting

provided.

Microphone: Dynamic mike containing

transistorized pre-amp or carbon

(must provide at least 120 mV rms

into 500 ohm load)

Sidetone: Adjustable up to 40 mw into 500 ohm

headphones.

Duty Cycle: 1 minute on, 4 minutes off (20%)

RECEIVER

Sensitivity: 1.5 uv (soft) will provide a 6 db

minimum signal plus noise ratio

(KHz, 30% mod).

Selectivity: Typical 6 db at +/- 7.5 KHz, 65 db at

+/- 17.5 KHz, 90 db at +/- 25 KHz.

Spurious Responses: Down at least 70 db

Ident Filter: 15 db minimum

AGC Characteristics: From 2 to 100.000 uV audio output

will not vary more than 1 db.

NAV Receiver Accuracy: Two sigma limit, +/- 1 degree

NAV Output: With LOC adjusted for 0.35 Vrms

VOR = 0.5 Vrms (typical) into 20K

ohms or greater load impedance.

DME Channeling: 2 x 5

G/S Channeling: 2 x 5

AUDIO

Auxiliary Audio Inputs: Eight 500 ohms with 30 db isolation

between any two.

Frequency Response: Within 6 db from 350 Hz to 2500

Headphone Output: 40 mw into 500 ohm

Speaker Output: 4.5 Vrms into auxiliary input

produces 5 watts audio output.

II. INSTALLATION

The MX385 is designed to be an exact replacement for the ARC RT385A and similar

units. As a replacement unit, the MX385 is inserted directly into the mounting tray for

the RT385A and tightened down with a long (11” shaft by .150” diameter) standard

screwdriver.

For new installations, ‘Installation Instructions’ for the RT385A should be used.

To remove the MX385 from the mounting tray it is important to note that the Channel

Selector knobs should not be used. The first step in removal is to ensure that the

mounting screw has been fully disengaged by rotating the mounting screw

counterclockwise with the tool described above. The unit should then easily slide

forward by grasping the sides of the front panel.

NOTICE TO INSTALLER

The TKM MX385 NAV/COMM is authorized by the FAA to TSO C34e, C36e, C37d, C38d, and C40c. The product is

an incomplete system. In order to achieve a complete TSO quality system, the MX385 must be installed to configure

in conjunction a TSO C37/C38 authorized antenna and a TSO C34 authorized navigation receiver. It is the

responsibility of the installer to ensure proper installation.

CONTINUED AIRWORTHINESS (HBA 98-18)

Permission is hereby given to installers approved by the recognized aviation authority to reference relevant excerpts

from the installation instructions provided by TKM, Inc. in order to fulfill documentation requirements for Instructions

for Continued airworthiness. Adequacy of the documents should not be assumed by this permission. Responsibility

for ICA documentation rests solely with the applicant. The MX385 product is ‘Repair on Condition Only’.

III. HOW TO OPERATE

Operating controls for the MX385 are located on the unit front panel or are remote inputs

through the rear panel.

The unit front panel is shown in fig. 1. The upper left-hand (yellow) COMM readout

indicates the active COMM frequency and the right-hand (red) COMM readout indicates

standby COMM frequency. The lower left-hand (yellow) readout indicates the active

NAV frequency and the right-hand (red) NAV readout indicates the standby NAV

frequency. A ‘tic’ readout is provided on the upper left-hand corner of the first digit of

each of the four frequency readouts.

The active COMM ‘tic’ indicates the presence of transmitter power.

The standby COMM ‘tic’ indicates that the Frequency Selection knobs will control

COMM standby frequency.

The active NAV ‘tic’ indicates that the NAV receiver is in the Ident mode.

The standby NAV ‘tic’ indicates that the Frequency Selector knobs will control NAV

standby frequency.

Power Application. The COMM volume control contains the master power switch and

activates both the NAV and COMM functions.

Frequency Selection. Then N/C button is used to activate either the COMM or the NAV

frequency selection as indicated by the appropriate “‘‘tic’’” display. The MHz and KHz

controls can then be used to select a desired standby channel. In COMM the ‘25’ button

is used to advance the frequency by 25 KHz.

After the desired standby frequency is selected it may be transferred to the active position

by pressing the Flip-flop button to the left of the ACTIVE display. The active and

standby channels will be interchanged each time the button is pressed.

Ident/Voice Selection. The ID\VC button can be used to select a tone filter in order to

receive voice signals on the NAV receiver. The switch is also used for frequency storage

as described below.

Test. The TEST button is a dual function switch. In normal operation, it is used to

override the squelch to verify receiver operation and to receive weak signals. The switch

is also used for frequency storage as described below.

Frequency Storage. The MX385 NAV COMM allows up to 50 NAV and 50 COMM

preset frequencies to be stored in the memory for recall. The use of memory presets is

described in the following sections.

Clearing all frequency presets. To erase all frequency presets with one operation,

simply turn on the power to the radio while holding the TEST button depressed.

Examining/Changing/Inserting/Deleting frequency presets. These operations on

individual frequency presets are accomplished in EDIT mode. To enter EDIT mode, turn

on the power to the radio while holding the VT button depressed. When the radio is in

EDIT mode, the ACTIVE displays show the reference number of the preset and the

standby displays show the actual preset frequency. After the ‘clearing all frequency

presets’ operation as described above, the only presets of 121.5 and the default NAV

preset of 112.0 are displayed.

EDIT mode operations are performed on either the COMM or NAV preset list, according

to where the tuning ‘tic’ indicator is displayed. The tuning ‘tic’ appears immediately to

the left of the COMM or NAV standby displays. Pressing the N/C button toggles

between NAV and COMM preset editing.

Examining presets (EDIT MODE). Pressing the COMM F-F button will step to the next

frequency in the preset list. Pressing the TEST button will step to the previous frequency

in the preset list. Pressing COMM F-F when the last preset is displayed will cause the

first preset to display. Similarly, pressing TEST when the first preset is displayed will

cause the last preset to display. Warning: When there is only one preset in the list, the

radio will not appear to “do anything” when the COMM F-F or TEST is pressed. This is

because the current, previous, and next presets are all the same preset.

Changing a preset (EDIT MODE). Press COMM F-F or TEST until the preset to be

changed is displayed. Dial in the new preset frequency using the tuning controls and

press either COMM F-F or TEST.

Inserting (Adding) a preset (EDIT MODE). Press COMM F-F or TEST until the desired

insert point is displayed (the new preset will be inserted AFTER this insert point). Dial

in the desired frequency using the tuning controls and press NAV F-F. Remember that a

preset list may contain a maximum of 50 entries. Inserting presets that would exceed this

limit are ignored.

Deleting a preset (EDIT MODE). Press COMM F-F or TEST until the preset to be

deleted is displayed. Then press the VC-ID switch to delete. If the deleted preset was

not at the end of the list, all the presets that followed it are renumbered. Each preset list

(NAV and COMM) must always contain at least one entry. If there is only one entry

remaining in a preset list, it may not be deleted (It can, however, be changed to another

frequency).

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