Intraplex® HD Link
Intraplex® HD Link™
Digital 950 MHz STL and Data Gateway
Our challenge: to design a studio-to-transmitter link (STL)
for your most demanding 950 MHz applications — one as
reliable and robust as Intraplex® T1 and IP audio links. Digital
STL manages much more than audio, so installation and
configuration need to be straightforward, not a science project.
Data should not be optional, requiring additional boxes and complexity. Your STL should be ready, out of the box,
for AM, FM and HD Radio™, as well as future multimedia applications.
Earlier digital STLs were not designed for IP data transport. Adding IP data to them required optional modules and external
add-ons, and many engineers working on HD Radio installations reported spending much time and money trying to
eliminate glitches.
Our solution: HD Link™ is designed to manage all HD Radio™ transport scenarios, regardless of where you place your importer
and exporter. Its two prioritized Ethernet paths give preference to HD Radio™ data over control and other LAN/WAN data. It
supports both UDP and TCP, and even handles the switching of TCP return packets over asymmetric IP paths with plug-andplay simplicity.
HD Link offers RF power to spare, an integrated IP gateway with sophisticated data handling capabilities, and multiple channels
of audio. The intuitive front panel and remote interfaces tap into the most complete feature set of any microwave STL, yet take
less time to configure. It can even operate on both RF and IP simultaneously, and allows automatic backup of all services from
one to the other.
Intraplex is broadcasting’s first choice for rock-solid, full-time operation of T1 STLs. With HD Link, you can now count on the same
dependable performance, superior support and long-term value for your microwave links.
Product Features
Powerful, reliable RF performance
Designed for data
■■ Up to 5 W of RF power
■■ Integrated IP channel with up to 1.5 Mb/s throughput for HD
Radio (importer-to-exporter or exporter-to-exciter)
■■ GatesAir-designed transmitter and receiver with 200, 250, 300,
375 or 500 kHz of RF bandwidth
■■ Low-density parity check (LDPC) coding advanced error
correction — requires less receive signal than Reed-Solomon to
achieve an equivalent bit error rate (BER), a critical parameter for
glitch-free HD Radio performance
■■ State-of-the-art modulation technology operates at 32, 64, 128 or
256 QAM, providing more than 3 Mb/s throughput under optimal
conditions
■■ Built-in circulator provides a high degree of isolation and VSWR
protection
Connecting What’s Next
■■ At least three times the nominal IP data throughput of other
digital STLs
■■ Does not require an external adapter to work with an external
TCP return path — suitable for use over private and public
networks
■■ Capable of taking advantage of available IP audio paths to
provide integral backup in the event of radio link failure
■■ Two prioritized Ethernet ports — high priority for HD Radio
traffic, low priority for control data and LAN traffic
■■ Each main program channel includes an RS-232 asynchronous
data channel, up to 9600 b/s
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Superior multichannel audio
performance
Product Details
■■ One or two stereo main program
channels, each available with linear
uncompressed or Enhanced apt-X®
compressed audio
The ability to do more
■■ User-selectable 32, 44.1, or 48 kHz
sample rates — transports 15, 20 or 22
kHz audio
■■ Two monaural, 7 kHz audio channels
with G.722 coding available for AM, radio
reading services, SCA, EAS and other
auxiliary audio applications
Easy setup and reliable operation
■■ Advanced Web browser user interface
and SNMP remote control
■■ Front-panel Ethernet port for access to
Web GUI and diagnostics
■■ USB port for saving configurations and
updating software
■■ FTP access for remote software uploads
■■ User-configurable control input and
alarm output contacts
Our RF and audio engineering teams
designed HD Link for maximum reliability
and to carry higher-quality audio and more
data over the STL path than was possible
with earlier 950 MHz STLs.
■■ More power
Sometimes you just need a little more
RF power to get the job done. Out of the
box, HD Link can operate at 1 W, 2 W, or
5 W, selectable in the field. It’s the most
powerful 950 MHz digital STL you can
buy.
■■ Advanced error correction
HD Link is the only radio STL using LDPC
coding for forward error correction (FEC).
This highly efficient scheme contributes
to increased data throughput.
■■ 21st-century design
By applying GatesAir know-how to the
technologies not available when legacy
STLs were designed, we optimized HD
Link for state-of-the-art performance with
minimal circuit noise.
Convenient connections and display
The advantages to you
■■ Intuitive front-panel interface
The combined benefits of more transmitter
power, LDPC error correction and enhanced
circuit design add up to as much as 10 dB
signal improvement over older digital STLs.
Depending on your requirements, this can
enable any or all of the following:
■■ XLR AES/EBU digital and L/R analog input/
output connectors
■■ Headphone jack on the receiver for audio
monitoring
■■ AES/EBU sync port on the receiver
■■ LCD level displays for all audio programs
at each end
■■ Analog level outputs for forward power
and reflected power (on transmitter unit)
and for received signal level and signal-tonoise (on receive unit)
■■ Optional main/alternate interface for
redundancy switching
■■ Use of smaller antennas, for less tower
load and lower costs
■■ Increased path distance
■■ Improved fade margin
■■ Operation at higher quadrature
amplitude modulation (QAM) orders for
increased carrying capacity
Sounds great
As with any Intraplex product, audio
quality is a top priority. Uncompressed
audio transport is fully transparent. In the
event bandwidth limitations require audio
compression, HD Link offers Enhanced
apt-X® coding to prevent the occurrence of
audio artifacts that can occur with multiple
generations of MPEG compression in the air
chain.
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Audio and data. And more data.
The architecture of HD Link starts with
an integrated IP gateway, the first in a
radio STL. This provides you with options
for nearly every practical combination of
audio, data, control and status used by
radio stations — as well as future media
applications. With the HD Link system’s
1536 kb/s of allocatable IP data, you’ll no
longer consider your STL to be merely an
audio transport system that happens to
provide some data options. In addition, an
asynchronous RS-232 serial data channel
accompanies each main program audio
channel for use with legacy control systems.
IP done right — the Intraplex way
If you like what Intraplex has done for you
with T1 and IP audio and data codecs, you’ll
love our implementation in HD Link. The
integrated IP gateway includes numerous
features:
Management Interface
(Front-panel display, HTTP, SNMP, FTP)
IP Layer
(Switching, tunneling, proxy ARP)
HD stream
(UDP/TCP)
Access
Control
LAN stream
(UDP/TCP)
Police
and
Shape
Scheduling
Analog
and AES
Audio I/O
One or more
channels of
analog or
AES audio
■■ IP prioritization allows it to carry other
IP data, such as control signals and LAN
traffic, separately from the high-priority
HD Radio stream.
■■ Dual domain access control provides
the tightest, most practical security. One
access list is for control of the HD Link
units Another manages the firewall that
keeps unwanted traffic off the transport
link.
■■ Layer 3 switching supports an
asymmetric TCP return path, allowing
integrated “plug and play” support for
TCP wherever a return path exists. Using
TCP allows quality HD Radio transport
under 30 times higher Bit Error Rate (BER)
conditions than UDP (3 x 10-4 for TCP
versus 10-5 for UDP).
■■ IP tunneling allows TCP return packets
with private addresses to traverse thirdparty networks like ISPs.
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HD Link IP Gateway Architecture
it typically provides about 3 dB improvement in link performance over
traditional FEC methods (Figure 2). While the mathematical principles
underlying LDPC have been understood for some time, only recently
have DSP chips become available with the speed and processing power
to run LDPC on digital STL signals in real time.
How HD Link Technology Improves Link Quality
3.5
500 kHz RF
3
Mb/s
2.5
In addition, whereas the performance of Reed-Solomon FEC falls off
directly if the link quality is degraded due to environmental or other
interference, LDPC maintains superior performance in the face of link
deterioration.
300 kHz RF
200 kHz RF
2
Further, where other STLs add a fixed level of FEC regardless of the
system configuration, HD Link uses adjustable amounts of FEC and
employs a sophisticated algorithm to calculate the optimum balance
between QAM order and FEC overhead to achieve the maximum data
throughput for any given configuration.
1.5
1
0.5
0
32
64
128
256
N+12
QAM Order
Figure 1. Higher-order QAM levels enable greater data carrying capacity
Forward error correction is a useful tool for improving link quality in
digital transmission. Essentially, it involves adding redundant data to
the transmission stream to allow the detection and reconstruction of
missing information. All digital RF STLs use some form of FEC, typically
using either the Reed-Solomon or the Viterbi coding method.
However, adding FEC increases the bit rate of the STL. Adding enough
extra bits may require the use of a higher QAM order, which places
greater demands on the link quality, thereby creating a Catch-22
situation — adding FEC to improve link quality may cause an increase in
QAM order, which requires yet higher link quality.
With HD Link, GatesAir has taken significant steps to improve this
situation.
Fewer
Errors
System Gain (dB)
N+9
Like most digital microwave systems, HD Link uses quadrature
amplitude modulation to maximize data throughput. All other factors
being equal, higher-order QAM can deliver more data using the same
RF bandwidth than lower-order QAM (Figure 1), but each step up in
QAM order requires about 3 dB to 4 dB better signal-to-noise ratio on
the RF link to maintain the same level of quality. RF link quality is thus
a critical factor in determining the amount of data that any given 950
MHz STL can carry.
N+6
LDPC
@5W
N+3
LDPC
@2W
N
ReedSolomon
@1W
LDPC
@1W
System Configuration
Figure 3. The combination of HD Link technology advantages
can offer you a dramatically improved STL system
The result? Combined with the increased performance afforded by its 5
W amplifier, HD Link can provide up to 10 dB of system enhancement,
right out of the box, compared with older digital STL systems (Figure 3).
Elegantly simple installation, configuration and operation
Your time is valuable, so HD Link is designed to make setup quick
and painless. The front-panel display is bright and clear, with easy-tounderstand labels. Menu hierarchies are shallow, so accessing most
functions takes only a few steps.
Bit Error Rate (BER)
Modem settings automatically synchronize between the transmitter
and receiver units. With both units set for the same frequency and RF
bandwidth, changes to QAM, IP bandwidth, etc., on the transmitter
automatically sync to the receiver.
HD Link has tools to help you in planning your overall STL system. Select
the active audio channels and IP bandwidth you want it to carry, and HD
Link automatically calculates the optimum settings for QAM and forward
error correction, along with the receive signal strength necessary to
achieve the desired level of throughput. These auto-calculated values
enable you to prepare a reliable path calculation and determine the
requisite transmitter power, antenna size and other variables.
3 dB
Typical
LDPC
Reed-Solomon
More
Errors
Higher
Link Quality
HD Link provides numerous interfaces for setup, diagnostics and
updates, with Ethernet and USB ports on each unit, plus remote access
via HTTP, FTP and SNMP.
Lower
Figure 2. The HD Link system’s advanced error correction handles
difficult links better than STLs using older technology
First, HD Link uses LDPC to do its FEC coding. LDPC is more efficient
than either Reed-Solomon or Viterbi, requiring less overhead data to
provide the same level of error correction; given the same overhead,
Connecting What’s Next
Additional convenience features include a headphone jack and AES/
EBU sync port on the receiver, and variable-speed fans to minimize
noise. And HD Link is physically compact at only two rack units per end.
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HD Link Transmitter Front Panel
Main/Alt interface for
redundancy switching
High- and
low-priority
Ethernet ports
GPI/O, forward
and reflected
power status
Antenna
connection
Analog and AES
inputs — program 1
Serial data
inputs
Analog and AES
inputs — program 2
Analog inputs for the
two mono aux program
Variable
speed fan
HD Link Transmitter Rear Panel
Built-in backup
When your HD Link is connected to a bidirectional IP network with sufficient bandwidth, the program channels will automatically switch to IP should
the 950 MHz link fail. In effect, HD Link is both a 950 MHz RF STL and an IP audio STL in one box, with automatic fallback from one to the other.
It’s easy to choose the HD Link that is right for you
To choose the right HD Link model for your STL, all you have to decide is how many stereo audio programs you need and whether you want linear
or Enhanced apt-X compressed audio. The auxiliary audio channels, control options, selectable output power, and data handling flexibility come
standard with every unit.
Choose from:
■■
IP plus one linear stereo program
■■
IP plus two linear stereo programs
■■
IP plus one Enhanced apt-X stereo program
■■
IP plus two Enhanced apt-X stereo programs
■■
IP plus two stereo programs, one Enhanced apt-X and one linear
■■
IP data and auxiliary audio only
HD Link Accessories
Bandpass filters
Single- and dual-cavity bandpass filters are available to attenuate interference at sites with congestion in the 950 MHz band.
Main/alternate interface
This system detects hardware and system faults in the HD Link transmitter and receiver, switching to an alternate pair should conditions fall out of
normal operational boundaries.
Connecting What’s Next
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Specifications
Specifications and designs are subject to change without notice
RF
Frequency
944 to 960 MHz fully synthesized
Step Size
25 kHz
Frequency Accuracy
±4 PPM (±0.0004%)
Occupied Bandwidth
200/250/300/375/500 kHz
Identifier
V-HDL950
FCC Emission Type
Designator(s)
200KD7W, 250KD7W, 300KD7W, 500KD7W
Modulation
Digital, 32/64/128/256 QAM
Antenna Connector
Type N (female), 50 ohms
Error Correction
LDPC
Error Correction Overhead
8 to 25% depending on mode
Transmitter
Power
1/2/5 W RMS
Monitoring
Forward power, reverse power, VSWR, PLL lock
Sensitivity
-95 to -82 dBm depending on mode
Dynamic Range
0 to -95 dBm
Spurious and Harmonic
Equalizer
24-tap feed-forward filter and 3-tap decision feedback filter
Monitoring
Receive lock, receive signal level, receive signal-to-noise ratio, PLL lock
Receiver
System
Delay
Main audio end-to-end delay is 50 to 300 mS based on mode. HD Radio™ and Ethernet end-to-end delay less
than 20 mS
Networking
Ethernet
■■
■■
■■
■■
■■
Up to 1.5 Mb/s UDP/IP or TCP/IP* transport (*TCP/IP transport requires an external IP return path)
Three 10/100Base-T, full-duplex, auto-negotiation
1 port for monitoring and remote control
1 port for high-priority data
1 port for low-priority data
Ethernet Connectors
3 RJ-45, each connector with integrated LEDs for link and activity monitoring
Protocols
IP, TCP, UDP, HTTP, FTP, NTP, Syslog, and SNMPv2c
IP Gateway
Port or IP based prioritization, static routing, proxy ARP, policing, firewall, public or private network for return
path
Control and Monitoring
Front Panel
Intuitive, graphical front-panel user interface 4.3 in. display, 480x272, TFT Color LCD with LED backlight and 7
button keypad
Remote User Interface
Monitoring and control using embedded Web server
Network Management
SNMP
VU Meter
Front-panel display, 6 segment audio level indicator for all audio channels
Contacts, Output
■■
■■
■■
■■
■■
Contacts, Input
2 input contacts, TTL compatible
Telemetry Output
■■ 2 analog outputs (0 to 5 V) for RF transmit forward and reverse power (transmitter)
■■ 2 analog outputs (0 to 5 V) for RF receive signal level and signal/noise ratio (receiver)
Contact/Analog Connector
26-pin D Sub and RJ-45
USB
1 USB 2.0 port for saving settings and software upgrade
4 output contacts with both normally closed and normally open outputs
2 output contacts: normally closed
Maximum current: 120 mA
Maximum voltage: 350 VDC
Closed resistance: 23 ohms typical
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Audio Monitoring
1 stereo 1/4 in. headphone jack (receiver)
Fault Detection and Logging
Internal log files, SNMP traps, syslog, and automatic upload of log files
Audio and Serial Data
Main
Main Digital Audio
Main Analog Audio
Channels
1 or 2 stereo program channels, individually configurable for linear or
Enhanced apt-X® audio
Sample Rate and Audio
Bandwidth
■■
■■
■■
■■
■■
Coding
Linear or Enhanced apt-X
Sample Size
■■ 16-bit (linear)
■■ 16/20/24-bit (apt-X)
Connectors
■■
■■
■■
■■
Digital/Analog Operation
■■ For input, digital/analog autodetection
■■ For output, digital and analog simultaneous
Data Channel
■■ RS-232 data transport 9.6 kb/s (linear)
■■ RS-232 data transport 1.2, 2.4, 4.8 and 9.6 kb/s, mode dependent (apt-X)
48 ks/s for 22.5 kHz operation
44.1 ks/s for 20 kHz operation
32 ks/s for 15 kHz operation
24 ks/s for 12 kHz operation (apt-X)
16 ks/s for 7.5 kHz operation (apt-X)
Audio Inputs: XLR female on left, right, and digital AES/EBU
Audio Outputs: XLR male on left, right, and digital AES/EBU
External AES/EBU Input Clock: RJ-11
RS-232 Data: RJ-11
Accepted Audio Sampling Rates ■■ Accepts any AES/EBU rate between 32 and 48 ks/s (linear)
■■ Accepts any AES/EBU rate between 24 and 48 ks/s (apt-X)
Rate Conversion
Rate converts any AES/EBU input rate to 48, 44.1 or 32 ks/s. In addition, for
apt-X, rate conversion includes 24 and 16 ks/s
External Sync (Receive Only)
Accepts external AES/EBU reference signal or RS-422 clock to synchronize
output to facility timing
Input/Output Impedance
Balanced, 110 ohms ±20%
AES/EBU Channel Status
A&B channel status bits are transported
Audio Frequency Response
±0.5 dB
■■ 48 ks/s: 1 Hz to 22 kHz
■■ 44.1 ks/s: 1 Hz to 20.5 kHz
■■ 32 ks/s: 1 Hz to 15 kHz
Audio Full Load Level
9 to +24 dBu
Crosstalk
Better than -80 dB
Total Distortion
■■ THD+N, less than 0.003% at 1 kHz – 1 dBFS input (linear)
■■ THD+N, less than 0.004% at 1 kHz – 1 dBFS input (apt-X)
Dynamic Range
■■
■■
■■
■■
Input Impedance
Balanced, greater than 10 K ohms
Greater than 91 dB (for linear)
Greater than 92 dB (16bit apt-X)
Greater than 105 dB (20bit apt-X)
Greater than 110 dB (24bit apt-X)
Output Impedance
Balanced, less than 52 ohms
Main Diagnostics
Test Tone Generator
1004 Hz test tone at -12 dBFS, which is equivalent to +8 dBm input
HD Audio
Integrated IP channel for UDP or TCP HD Radio (importer-to-exporter or exporter-to-exciter)
Connecting What’s Next
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Auxiliary Audio
Channels
2 analog
Sample Rate and Audio
Bandwidth
16 ks/s for 7.5 kHz operation
Audio Connectors
■■ Audio Inputs: XLR female
■■ Audio Outputs: XLR male
Coding
ITU G.722 mode 1
Sample Size
14-bit
Audio Frequency Response
100 to 6400 Hz ±1 dB
Data Rate
64 kb/s per active channel
Total Distortion
THD+N, less than 0.1% at 1 kHz to 1 dBFS input
Dynamic Range
Greater than 65 dB
Input Impedance
Balanced, greater than 10 K ohms
Output Impedance
Balanced, less than 52 ohms
Mechanical and Environmental
Dimensions (H X W X D)
■■ 2RU: 3.5 x 19 x 14 in. (8.9 x 48.3 x 35.6 cm)
■■ EIA rack mountable
Weight
■■ Transmitter: 18.5 lbs (8.4 kg)
■■ Receiver: 14.5 lbs (6.6 kg)
Power Requirements
Universal AC 100 to 240 VAC, 50/60 Hz
Power Consumption
■■ Transmitter: 104 W maximum
■■ Receiver: 34 W maximum
Fuse Protections
2A AC input fuse
Cooling
Forced air using variable-speed internal fan
Humidity
To 95% non-condensing
Operating Temperature
32º to 122º F (0º to 50º C)
Compliance
Regulatory Compliance
■■ FCC Part 15
■■ FCC Part 74, subpart E
■■ EN60950
Connecting What’s Next
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INTRAPLEX_HD_LINK_KA_0915
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