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EchoLink
Amateur Radio meets
Voice over the Internet Protocol
Andy Zwirko – K1RAhttp://go.to/[email protected]
OverviewVoIP 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
K1RA-L 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)
A/D – D/ATerms 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 / DecodeCompress / Decompress
Codec Types GSM (E/L 8kbps) uLaw aLaw ADPCM
Function Don’t send dead air Combined similar values Save space and time
Internet and IP
HostsRouters
Dotted Decimal AddressesTransport (TCP/UDP)Source & Destination PortsData / BuffersChecksum
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 OverviewLink 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) 2700 Active Nodes Worldwide 552 Users, 1064 Links, 962 Repeaters, 122 Confs.
VoIP Network Topology
68.54.3.2
128.10.60.73
209.176.50.1
212.50.33.5 141.9.5.102
K1RA
WA3NAN-R
K1HTV
NA3J/0
PC to PC
Sys Op Mode
Simplex Link
Repeater Link
PC Users, Links, Repeaters
EchoLink - The Software
Windows
Mac
Linux
Sysop
User
Interfaces
Types Commercial Homegrown
Function Isolate Attenuate Match Key PTT COR
Commercial Interfaces
DIY Interface Schematic
K1RA-LEcholink node #199756
Warrenton, VA – FM18cr - ~ 550ft ASL
144.440 MHz Simplex - ~20w
Adelphia Cable ISP - 4Mbps / 512Kbps
Supports 4 simultaneous users
Software version 1.980
Access is Open 24/7
Node Hardware
Radio Equipment
•ICOM IC207H
•20 Watts
•5/8ths vertical @25ft
•12v 20A P.S.
Computer Equipment
•Pentium II – 350MHz
•192 MB RAM
•6 GB Hard Disk
•10baseT NIC
•Linksys D614+ FW
•2000VA UPS
Control Operation
3 Levels of ControlDTMF over Link FrequencyHTTP Web InterfaceDirect PC Keyboard
Control OperatorsK1RA - AndyKZ1AMY - Amy
Node DTMF Commands
Status – 08
Connect – 4, 5, 6 digit node numberEcho Test Server = 9999short cuts, ex: *90 = WA3NAN-R
Disconnect - #
Reconnect – 09
Help File -*411
Good Operating Practices
Identify YourselfWhen connectingWhen sending DTMF
Pause, Wait, ListenUse DTMF Status Command 08
Rag chewers beware3 minute timeout
Common Problems
Connection Timeout
Disconnects
Audio issuesBrokenGarbledDrop outs
Local EchoLink Nodes List
Local EchoLink Nodes Map
