Inside
Echolink
Amateur Radio
meets
Voice over the Internet Protocol
Ron P. Milione – W2TAP
w2tap@arrl.net
ron.p.milione.ctr@us.army.mil
Overview
VoIP Concepts and Terminology


Analog, Digital, Samples, Buffers
Packets, Client/Server, TCP/IP
Ham VoIP Projects


Access, Modes, Connecting, Audio Quality
Topology, Users, Is this ‘Ham Radio’?
EchoLink Software Graphical User Interface


Setup, Radio, Computer
Modes, Configuration
Radio Interfaces
W2LV - Live Node Demo


Good Practices
Common Problems
What is VoIP?
Convert Voice to Digital 1’ 0’s (A/D)
Compress Digital Data (Encode)
Buffer digital sample data into packets
Send packet buffers via Internet Protocol
Receive and assemble packet buffers
Uncompress Digital Data (Decode)
Convert Digital 1’s 0’s to Voice (D/A)
What is THIS Echolink?
EchoLink uses VoIP (Voice Over Internet Protocol) to
allow licensed Amateur Radio Operators to communicate
with other Amateurs via the Internet.
It is primarily a Windows based application and is offered
free of charge at http://www.echolink.org.
There is also a new EchoLinux and EchoMac available.
It was developed by Jonathan Taylor (K1RFD) in 2002
(He received Hamvention 2003 Special Achievement
Award).
A/D – D/A
Terms and Concepts
Analog <> Digital


Continuous <> Discrete
Air Pressure <> Volts
Sampling Rate


Freq. (KHz) 8, 11, 22, 44
Unit time (secs)
Sampling Bits


Quantization (#) 2^8, 2^16
Dynamic range (dB) 50, 98
Nyquist Theorem

Sample Rate >= 2 x Freq.
Encode / Decode
Compress / Decompress
Codec Types




GSM (E/L 8kbps)
uLaw
aLaw
ADPCM
Function



Don’t send dead air
Combined similar
values
Save space and time
What Modes Are
Available?
EchoLink can be operated strictly between two
computers connected to the Internet using the PC
soundcard with Speakers and a Microphone.
EchoLink can be interfaced to a standard FM transceiver
as a “simplex link” from your home QTH.
EchoLink can be interfaced to a VHF or UHF repeater for
more coverage.
Internet and IP
Hosts
Routers
Dotted
Decimal
Addresses
Transport
(TCP/UDP)
Source &
Destination
Ports
Data /
Buffers
Checksum
Connecting via VoIP
Two methods / implementations

Client / Server (Middleman)
Client is Authenticated (Callsign / Password)
 Client Requests Users List ( Callsign, IP Addr.)
 Client Makes Connection to User


No Central Server (Client to Client)
Client Must manually obtain remote IP Addr.
 Client Makes Connection to User

Amateur Radio VoIP Projects
EchoLink – http://www.echolink.org/
IRLP – http://www.irlp.net/
CQiNet – http://cqinet.sourceforge.net/
WIRES II – http://www.vxstd.com
eQSO – http://www.eqso.net/
Echolink Overview
Link Radio Amateurs via the Internet
 PC-PC Users, PC-RF Gateways, RF-RF
Simple Password Access to Server
 “By Hand” Callsign check for Password Validation
GSM Vocoder 8kbps/user
 Lower Voice Quality (Dial-up or Broadband ISP)
Multiple Connections per Node Possible
 Bandwidth Limited (Broadband Required for Conf)
Node Information (http://www.echolink.org/logins.asp)
 4715+ Active Nodes Worldwide
 1050 Users, 1464 Links, 1113 Repeaters, 192 Confs.
VoIP Network Topology
209.176.50.1
68.54.3.2
W2TAP
128.10.60.73
WA2CDL
212.50.33.5
141.9.5.102
W2LV
W4AJX
PC to PC
Sys Op Mode
Simplex Link
Repeater Link
PC Users, Links, Repeaters
EchoLink - The Software
Windows
Mac
Linux
Sysop
User
And now -- The Software…
Here is the main
Screen, listing the
Stations currently
on the Link, by
Country, Call
Zone etc.
The Bottom of the Screen shows the current Transmit and Receive Audio
levels in a colored bar graphic.
Basic Setup
The first thing to
do after installing
the software is to
configure your
Station Setup.
The first time you use Echolink, you will have to wait to be validated,
before you are connected to the EchoLink server.
Audio Setup
This includes
your Audio
details, for the
PC Speakers and
Microphone.
Connection Setup
This Screen allows
you to configure the
various Internet
connections you are
willing to accept.
The Two Pc Audio
Screens
This is the Output
This is the Input
Interfaces
Types


Commercial
Homegrown
Function

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
Isolate
Attenuate
Match
Key PTT
COR
Commercial Interfaces
DIY Interface Schematic
W2VL
Echolink node #487981
Call Node Location/Connection
Status W2VL-R 487981 LIMARC,
GlenOaks, NY (1) ON
40.7470463 -73.7115199
146.850MHz (-) Offset Duplex
Supports 4+ simultaneous users
Access is Open 24/7
IRLP ID: 4438
W2KPQ
Echolink node #503075
Call Node Location/Connection
Status W2KPQ-R 487981 LIMARC,
SELDEN, NY (1) ON
40.8664873 -73.0356625
147.3750MHz (+ offset) Duplex
Supports 4+ simultaneous users
Access is Open 24/7
IRLP ID: 4478
Control Operation
3 Levels of Control
DTMF over Link Frequency
 HTTP Web Interface
 Direct PC Keyboard

Control Operators
LIMARC
 WA2CDL - Andy

Node DTMF Commands
Given as an example
Status – 08
Connect – 4, 5, 6 digit node number
Echo Test Server = 9999
 short cuts, ex: *90 = WA2CDL-R

Disconnect - #
Reconnect – 09
Help File -*411
Good Operating Practices
Identify Yourself
When connecting
 When sending DTMF

Pause, Wait, Listen

Use DTMF Status Command 08
Rag chewers beware

3 minute timeout
Common Problems
Connection Timeout
Disconnects
Audio issues
Broken
 Garbled
 Drop outs

W2VL REPEATER
W2KPQ REPEATER
Local EchoLink Nodes List
Local EchoLink Nodes Map
Question?
Tnx & 73 !
Ron Milione Ph.D.
w2tap@arrl.net
ron.p.milione.ctr@us.army.mil