Marconi 915 User Guide

HF AIRBORNE TRANSCEIVER

Extensive research and development
activities by Marconi Selenia
Communications in the HF field have
led to the design and production of
advanced HF/SSB system for fixed­wing aircraft and helicopters.

These transceivers provide
voice/data radiocommunications for
airborne applications over the 2 to
30 MHz frequency range.

Designed to meet the most
diverse requirements,they
provide various output power
possibilities (from 100 W to 400
W) and a wide range of
voice/data services in the
USB/LSB/AM and CW modes.

Data communication
capabilities include Link-11,
as per STANAG 5511.

The components of this HF systems
family has been specifically designed
for airborne applications,where a
very tough EMI environment is
expected,such as in co-located
installations requiring simultaneous
operation of several radios (i.e.
voice/data) on the same airborne
platform.

Storage of operation-related data
reduce the operator workload
during the mission phase.

Maintenance is simplified by
advanced BITE facilities
allowing failure isolation down to
module level.

Extensive flight tests on helicopters
and fixed-wing aircraft have
demonstrated excellent
performance in the most severe
environments.

All the systems ar powered by
115Vac / 400 Hz 3-phase power
line, but there is also a DC
powered version of the SRT-[170,
270]/L version,i.e. the SRT-170/M
system,which is suitable for
installation in very severe EMI
environments.

The SRT-170/M combines high
flexibility and simplified operation
in a reduced size and weight
package, achieved through
innovative electrical and
mechanical design.

The receiver/exciter and RF
amplifier are assembled into a
single, 1/2 ATR sized LRU.

All these HF systems are currently
in service on several airborne
platforms.

Any of these transceivers can be
interfaced with various Antenna
Tuning Units (ATU) dedicated to
Loop,Wire or Notch antennas.

As an example, a typical
configuration for helicopter
installation includes an externally
mounted ATU (ATU-1992, an
aerodynamically shaped unit,suited
for external installation on the
fuselage of low-speed aircraft),
and a Loop antenna.

The external ATU installation
reduces the problems
of EMI with other equipment
onboard.

The Loop antenna allows use of HF
ionospheric propagation in the
‘Near Ver tical Incidence Skywave’
(NVIS) mode.

The combination of NVIS and
surface-wave modes provides
reliable radio communication over
adverse terrain.

DESCRIPTION

HF AIRBORNE TRANSCEIVERS

SRT 170-M

SRT 470-L

A typical HF system consists of the
following units:

• Receiver/Exciter

• Power amplifier

• Pre- post-selector (option,only
to meet severe co-location /
simop requirements).

• Mounting tray.

• Antenna Tuning Unit (ATU)
See table above for a complete

list of available system
components.

The HF system provides simplex
receive/transmit operation over the
2 to 30 MHz range.

Mission-oriented data are stored in
the SRT-170/M including

frequency, mode, and time of
operation.

The ATU is able to store up to 256
channels.Antenna tuning

data are acquired and stored prior
to the mission. When any of the
stored channels is selected during
the mission,the stored tuning data
are used to speed up the antenna
tuning operation,without power
emission (‘silent tuning’).

By using this approach,tuning
times of the order of 50 ms are
achieved.

Status signals are made available by
the HF system for a central aircraft
maintenance panel,allowing quick
maintenance.

The BITE function of the modules
is designed to allow tests and
checkouts by automatic test
equipment (ATE) and fast,

faulty-unit repair at the
maintenance organisation level.

The HF system can be controlled
via either MIL-STD- 1553B,or

ARINC 429 data bus,or from a
dedicated Remote

Control Panel (SP-648/L).
The HF System can interface to the

following devices:

• Adaptive Communications
Processor, for automatic selection
of the best operating frequency,
based on data on the channel
conditions

• Data Link Modem,to set up
point-to-point and network links

• Crypto Modem, to operate in the
crypto voice narrowband mode.

CONFIGURATION

OPERATION

• Voice and data operation

• Adaptive communication (ALE),
according to MIL-STD-188-141A

• SELCAL function i.a.w.ARINC 714

• Microprocessor control and LSI
component design

• Direct Digital Synthesis (DDS)
technology for fast frequency
setting

• Digital Signal Processing (DSP)

• 100W systems built in a single,
compact unit of 1/2 ATR-short

package, which combines
receiver/exciter and power
amplifier functions

• Use of whip,wire, loop or
structural antennas by using the
appropriate ATU

• 100 presettable channels

• FSK mode by optional internal
modem

• Extensive,continuous and
interruptive BITE to locate failures
and minimize turnaround time

• Modular construction combined
with advanced BITE facilities for
quick,simple and economical
maintenance

• Crypto voice by optional external
modem

• Fast,automatic tuning

• Embedded growth capability for
EPM/ARCS and high-speed serial
modem

• Complete remote control for all
operating functions,through bus
interface or dedicated control panel

MAIN FEATURES

OVERVIEW OF HF SYSTEMS COMPONENTS LRU

Systems Systems Description Power Supply Dimensions (mm)
Types Components Mass (Kg)

W H D M
SRT-170/M 100W lightweight HF system. + 28Vdc
(SRT-170/L) Note that the SRT-170/L version

is powered by 115Vac / 400 Hz 3-phase

RT-170/M 100 W,lightweight,HF transceiver,includes internal 124 193.5 360.5 9

Receiver/Exciter and Power Amplifier
SP-1127/L ATU for Wire antennas 124 193 457 7
SP-1992 ATU for Loop antennas 115 323 367 4

SRT-270/L 200W HF system 115Vac / 400 Hz

3-phase

SP-649/L Receiver/Exciter 90 197.5 320.5 6
SP-480/L1 200W Power Amplifier 90 197.5 320.5 6
SP-1325/L Pre-post selector (optional) for loop and notch antennas. 92 200 361 3.2

Used to meet severe constraints of co-location

and simop requirements
SP-1992 ATU for Loop antennas 115 323 318 4

SRT-470/L 400W HF system 115Vac / 400 Hz

3-phase
SP-649/L Receiver/Exciter 90 197.5 320.5 6
SP-484/L 400W Power Amplifier 257 193.5 320.5 15
SP-1325/L Pre-post selector (optional) for loop and notch antennas. 92 200 361 3.2

Used to meet severe constraints of co-location
and simop requirements

SP-1325/L1 Pre-post selector (optional) for wire antennas. 92 200 361 3.2

Used to meet severe constraints of co-location

and simop requirements
SP-1992/LM4 ATU for 400W Wire antennas 257 193.5 498 13
SP-1999 ATU for Loop antennas 213 429 604 14
SP-1992/LN ATU for Notch antennas 190.5 193.5 360 8.5

TECHNICAL CHARACTERISTICS

GENERAL
Frequency range 2 to 29.9999 MHz

Tuning time Typical 1s (including ATU); 50 ms on learned channel
Modes of operation Simplex Rx/Tx on any available channel
Modulation Clear and secure voice (USB/LSB/AM),CW (USB),Link-11 data (USB,LSB,ISB),TTY (USB), SELCAL

(Arinc 714-6), ALE (8-FSK)
Preset channels 100 (stored in the Control Panel)
Frequency stability 1 part in 10

7

Power supply 115 Vac / 400 Hz 3-phase,

except for SRT-170/M powerd by +28 VDC
Power consumption dependent on system type (as an example,for a 400W, fully configured,system)
Tx: 1500W
Rx: 150W
Dimensions & Mass See table 1
Environmental conditions:
General: MIL-STD-810C (temperature,altitude,vibration,shock,salt,fog)
Operating Temperature: -54°C to + 55°C
Altitude: 70’000 ft

TRANSMISSION
RF output power for the 170 family:175W PEP / 85 W average

for the 270 family:200W PEP / 100 W average

for the 470 family:400W PEP / 400 W average
RF power selection 1/2 or 1/4 of max RF output power selectable
Intermodulation (linearity) Better than 30 dB below each of the two-tone
Harmonic attenuation (in band) Better than 50 dB below PEP
Spurious suppression Better than 60 dB below PEP
Carrier attenuation in SSB mode Better than 50 dB below PEP
Undesired sideband attenuation Better than 50 dB below PEP
Duty cycle 1 minutes Tx and 5 minutes Rx in CW,AM

and Data mode; continuous in SSB Voice

and Link-11 mode
Audio input Voice: 0 dBm/600 ohm balanced
Data: 0 dBm/600 ohm balanced
Crypto voice: 0 dBm/600 ohm balanced
RF Output Protection Automatic protection against short circuit or open circuit of the RF output path and against over temperature

RECEPTION
Sensitivity for 10 dB min.(S+N)/N

CW/SSB: 0.7 µV
AM: 2.5 µV
Selectivity not more than 3dB down from Fc ±300 Hz to Fc ±3050 Hz
Image rejection Better than 100 dB
IF rejection Better than 100 dB
Cross-modulation Better than 3% of nominal audio output
Input impedance 500 ohm (nominal) unbalanced
Intermodulation (linearity) Better than 35 dB below the output level of either tone
Desensitization 3 dB max.

AGC (figure of merit)

Voice: ±3 dB max output audio variation for input variations between 10 µVrms and 1 Vrms
Data: according to STANAG 5511 / ML-STD-188-203-1A

AGC time constants

Voice: 12ms max rise time,1.5s max fall time
Data: LINK-11 according to STANAG 5511

Audio output

Voice: 100 mW/600 ohm or 150 ohm balanced

Data: 0 dBm/600 ohm balanced
Audio distortion Better than 5%
Squelch Voice SSB: adjustable for (S+N)/N = 5 to 20 dB

Marconi Selenia Communications S.p.A.

Viale dell’Industria,4 - 00040 Pomezia RM
Tel. [phone] - Fax [phone]
e-mail:[e-mail]

Via A.Negrone 1/A - 16153 Cornigliano GE
Tel. [phone] - Fax [phone]

Marconi Selenia Communications Ltd

Marconi House,New Street,Chelmsford,CM 1 1 PL - UK
Tel. [phone] - Fax [phone]

Marconi Selenia Communications GmbH

Gartenstrasse, 106 - 71522 Backnang - Germany
Postfach (P.O.Box) 1980 - 71509 Backnang
Tel. [phone] - Fax [phone]

Marconi Selenia Communications Romania Srl

8,Dr.Louis Pasteur - 76206 Bucharest - Romania
Tel. [phone] - Fax [phone]

Marconi Selenia Kominikasyon A.s.

Konya Yolu Km. 25 - 06830 Golbasi (Ankara) - Turkey
Tel. [phone] - Fax [phone]

Marconi Selenia Communications Do Brasil

Brasilia (BR) - SHIS Q126 Conj 5 Casa 4 Bairro:
Lago sul Brasilia DF CEP 71670-050 Brasil
Tel. [phone] - Fax [phone]

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Selenia Communication S.p.A.in writing) may not be used,applied or reproduced for any pur­pose or form part of any order or contract or be regarded as a representation relating to the
products or services concerned. Marconi Selenia Communication S.p.A. reserves the right to
alter without notice the specification,design or conditions of supply of any product or service.

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