AP2HA

AMATEUR RADIO STATION , ISLAMABAD , PAKISTAN

DIGITAL MODES

^{Common Digital Modes in Amateur Radio are RTTY , AMTOR , PACTOR , G-TOR , CLOVER , PSK-31 and PACKET RADIO etc .}

^RTTY:-

^{It is the original data communication mode. RTTY is better suited for "roundtable" QSOs with several stations. It is conversational or "chat" mode and uses the ITA2 code to send a limited text alphabet , using frequency shift keying. Two tones are used 170 Hz apart for amateur applications. The transmission is about 450 Hz wide. Amateur Radio operation is at 45.45 baud. Now using sound card and PC , interfaced with a suitable rig , you can enjoy RTTY. Many softwares are available for rtty using Sound Card . Most popular is the TrueTTY by Sergei , UA9OSV.}

^AMTOR:-

^{AMTOR is an error correcting mode. It is the abbreviation of Amateur Teleprinting Over Radio. It stands on SITOR mode ( used in marine communication). A transmitting station sends three characters then waits for a response from the receiving station. The receiving station sends a ACK ( send the next three characters ) or a NAK ( repeat the last three characters ). This exchange of ACKs and NAKs ensure that only error-free text arrives at the receiving station.}

^PACTOR:-

^{PACTOR is a packet-like mode based on AMTOR but with slightly longer packets and AX.25 compatibility. This mode is much faster than AMTOR.}

^G-TOR:-

^{The "G" in G-TOR stands for "GOLAY" a kind of farwarding error-correction coding. G-TOR uses several compression , checking and correction techniques along with automatic repeat request.}

^{PACKET RADIO:-}

^{In this mode data is broken into "packets" of data by a TNC ( Terminal Node Controller ) , before sending these packets over the radio , the TNC calculates each packet's checksum . On the received end a TNC checks packets for accuracy and requests for retransmission of bad packets to ensure error-free communication. Thousanads of packet radio stations have formed a worldwide network.}

^CLOVER:-

^{It is a relatively new digital mode. It utilizes a four tone modulation system and digital signal processing ( DSP) to pass data on the HF bands at a rate much faster than AMTOR}

^PSK-31:-

^{PSK-31 was developed recently as an RTTY replacement. It is much more sensitive than RTTY and uses less bandwidth than almost any other mode. It uses differential phase shift keying ( BPSK or QPSK ) and only single tone is used. PSK-31 is very popular and has proved to be excellent for HF and VHF DX. There are many softwares available for PSK-31 like simple G3PLX programme PSK-31 SBW and DIGIPAN. These programmes can be easily downloaded from Internet.}

MT63:-

^{MT63 is a new DSP based mode for sending keboard text over paths that experience fading and interference from other signals. Sixty four PSK carriers are transmitted all at once , each one carrying a different part of the transmitted signal. The data is spread across the width of the asignal and also spread in time , so MT63 is resistant to both time and frequency related interference. The PC version by IZ8BLY is very simple and easy to tune. It is extremely robust. It is an excellent mode for transmitting bulletins.}

^{Recommended Frequencies on 20m, 15m and 10m: 14.347 , 21.130, 28.130}

^{HELLSCHREIBER:-}

^{This mode is very old , but the use of PC with sound card has made it very simple. text and simple graphic symbols are transmitted uncoded , rather like sending the dots to a dot matrix printer. There are several Hell modes in general use .User selectable fonts are available for transmission. The most commonly use mode is FELD-HELL. The best HELL software is IZ8BLY HELLSCHREIBER. It operates in seven HELL modes.}

^{Recommended Frequencies:( IN LSB ) 10.135 , 14.063 , 21.063 , 28.063}

^{An image of FELD HELL during the QSO of YO8FR with AP2HA}

^THROB:-

^{It is also a new DSP sound card mode , using 5 tones signals. Software has been written by G3PPT and is available on internet.}

^MFSK16:-

^{It is an advancement to the THROB mode , and encodes 16 tones. MFSK8 is also available with a lowre baud rate ( 8) but greater reliability for dxing when proper phaseshift is a major problem. Both versions are available in " STREAM" created by IZ8BLY. It is freeware programm}

Understanding Soundcard Interfacing
by Ernie Mills, WM2U. http://www.qsl.net/wm2u