The computing ability of PC's and their soundcards has allowed the emergence of a myriad of digital modes enduring a severe competition and prone to constant evolution. Yesterday favorites become rarely used (MT63 for instance) while new sophisticated ones are quickly adopted (as Olivia) or ignored (CHIP) while veterans achieve a classic status though their performances are not the bests like RTTY.
After having interfaced his transceiver to his PC the beginner will be confronted to try to know what he is listening to or looking at or to where in the bands he should look for a particular mode. Interfacing, frequencies and modes description can be found in the helpfiles of Multipsk http://f6cte.free.fr/ which is a powerfull, well documented and free software.
Basically, modes differ by modulation type (remember the old classics amplitude, frequency and phase), the way they insure synchronisation between the transmitter and the receiver and the error correction technique they use. This leads to different performances that will be briefly discussed for my favorite modes on an empirical point of view.
PSK is the most widespread mode. It's the one to begin with, sensitive, easy to tune, narrow which makes the use of CW filters effective.
The availability of multiple parallel QSO's reading is a powerfull tool for spotting great DX in crowded bands like 20 m.
Main drawback is its poor performances on polar paths or very long haul. Let's say it : PSK is great for exchanging minimal information on DX or chatting when no more then 2 hops are needed but it's not a long distance chat mode. A less confidential use of PSKFEC could improve this situation.
PSK signal quality is very sensitive to overmodulation as can be endured on the bands. Have a look here to understand what splattering means http://www.mymorninglight.org/ham/psk.htm . Ask for an IMD report and/or build a PSKmeter to monitor your signal http://www.ssiserver.com/info/pskmeter/.
Concise, easy to tune, rather resilient to difficult propagation conditions and QRM provided the signal strength is very high, RTTY remains DXers and contesters favorite. It's lack of sensitivity is compensated by the widespread of brute force :Power Amplifiers...
MMTTY is a must software for serious enthusiasts http://mmhamsoft.ham-radio.ch/
|Tough conditions on 40 m, strong fading 1 hour after sunrise|
Hell transmitted letters are painted on the screen rather than decoded. The use of your brain, the most sophisticated decoding tool, makes it effective for DX if ionospheric distortion is not too strong. It's easy to recognize and to tune, slow and unfortunately not widespread. It has an old-fashioned taste that I love.
IZ8BLY's software is great http://xoomer.virgilio.it/aporcino/.
MFSK sounds like a North African flute. Sensitive, quick, resilient. It can be heard now and then but weak signals are easier to recognize than to tune.
Try Stream for a dedicated software http://xoomer.virgilio.it/aporcino/.
Olivia is by far my favorite. It's the only one to allow long chats nearly every day (in this time of low solar activity) from Europe to Pacific. It's exceptionnally sensitive and robust, not very easy to tune and the use of channels (which could be used in other modes like SSB...) is mandatory as this mode is able to read what can (nearly) not be heard.
Olivia needs patience and respect which make it nearly impossible to use when everybody want to give a try.
Frequency standards are indicated in the reference page to make sure that your transceiver is correctly calibrated.
There is no need to use modes wider than 500 Hz on 40 and 80 m .
Channels frequencies are the frequencies you dial, it is not the effective frequency used. Multipsk and MixW use a 500 Hz basis tone. If you choose Olivia 32/1000, your transmission will take place between 14107.5 (example dial frequency) 500 Hz and 14107.5 1500 Hz so between 14108 and 14109 kHz.
Should you change to the 16/500 mode, your transmission will be between 14107.5 500 and 14'107.5 500 500 so between 14108 and 14108.5.
So dialed frequencies for the 32/1000 mode used on 20m are 14'106.5, 14'107.5, 14108.5.
On 80m they are (for 16/500 or 8/500) : 3842, 3842.5, 3843, 3843.5 etc.
Unattended Pactor or packet stations tend to occupy the same frequencies. Olivia's resilience can cope with them up to a certain level.
Click here for a ocmplete list of Olivia QRG hflink.com/olivia
|Dialing frequencies and channels in Olivia mode|
Listen on 14'076 kHz, you will hear a strange slow musical not unlike mfsk. This is the mode used to try long haul minimalist qso's under the current low solar activity conditions. Have a look here for decoding software and further information.
The transmission of pictures is also impacted by digital techniques. Have a look on DIGTRX and make trials http://paginas.terra.com.br/lazer/py4zbz/hdsstv/HamDRM.htm
for those who prefer to chat with their voice ...