By Eddie Pierce, WB6DFW
The digital modes provide a wonderful opportunity for those of us who would like to work on the HF bands but find CW too difficult and SSB phone prohibitive because of interference problems. These modes require very little power to work the world. Generally 25 to 50 watts is plenty of power. The digital modes are comparable to CW in that their bandwidths are very narrow. Bandwidths generally range from about 30 to 200 Hz compared with SSB which is 2,100 Hz. This is a huge difference and one of the main reasons why the digital modes are so effective at low power. Because of their low power and modulation schemes, the digital modes do not interfere with telephones and answering machines in the neighborhood the way the SSB often does.
The digital modes are easy to set up and get operating. What is needed is an HF rig, a computer running one of the many software programs that are available either for free (most are) or for a small purchase price, and a hardware interface between the computer and radio. Most computers come with a sound card and these modes work via the sound card input and output circuits. A fairly easy interface between the sound card and radio can be built for around $7.00 or a very nice and very adequate interface can be purchased that will handle any chore you might throw at these modes.
Best of all, the digital modes are incredible easy to use. The major software programs utilize a waterfall display that shows all of the signals currently operating on the band. All you have to do is click on a signal with your mouse, and the QSO pops up on your computer screen. It doesn’t get any easier than that.
The digital modes described in this article are mainly found on the High Frequency bands and will require a General class license or above (except on 10 meters where a Technician with morse code privileges can operate from 28.100 to 28.300 MHz).
There is a wide choice of digital modes to choose from. However, the most popular modes today are PSK31, BAUDOT (RTTY), MFSK-16, and PACTOR. PSK31 is the most popular of the digital modes because it is very effective at low power, is easy to set up (it requires only an HF radio and a computer with a sound card), and its waterfall display makes it extremely easy to use. Baudot RTTY is the second most popular, particularly for DX and contest work. RTTY is the oldest of the digital modes. However, new software with waterfall displays and using the computer’s sound card as the HF radio interface has given the old standby a new look. MFSK-16 is one of the newest modes that shows considerable promise. It is a good weak signal performer, reportedly better than PSK31, particularly for DX contacts that involve signal paths that pass through the Earth’s polar regions. It is a little more difficult to operate than PSK31 but does use a waterfall display and sound card radio interface. PACTOR is the most popular of the error correcting class of digital modes that includes AMTOR, Clover, and G-TOR. These modes utilize relatively complex protocols that automatically detect and recover from transmission errors through a combination of forward error correction and automatic retransmissions. They are excellent for message handling in that they deliver error free text to the computer screen. However, they are more than what is needed for most casual amateur radio QSOs. Because of their complex protocols, these modes require a multi-mode hardware controller box between the computer and HF radio. The multi-mode controller makes these modes more expensive to implement and a little more difficult to operate than the modes using waterfall displays and sound card interfaces. One point to mention about the sound card interface is that once you have it installed, you can switch between the various modes that use the interface (PSK31, RTTY, MFSK-16, and others) by simply activating the appropriate software package on your computer.
Where on the HF bands do you find hams using the digital modes? The following chart shows you were to look.
Where do you find the interface hardware and software that you need? 90% of the digital mode hams are using RIGblaster as the hardware interface and either MixW or Digipan as the digital mode software.
RIGblaster is the easiest way to properly connect a radio to a computer’s sound card. RIGblaster provides adjustable impedance and level matching between the sound card and the radio’s audio input and outputs. Without proper impedance and level matching, a sound card can overdrive the radio’s modulator resulting in a "dirty" wide bandwidth signal being transmitted that will annoy others on the band. RIGblaster also eliminates the need for a separate transmit/receive switch and permits easy switching between digital modes and SSB voice operation. RIGblaster is available in several models ranging in price from about $60 to $140. My choice is the RIGblaster PLUS at $140. This interface handles all aspects of the digital modes from rig control to sending CW using your computer keyboard. RIGblaster is built by West Mountain Radio and can be purchased through AES Ham Radio catalog (telephone number 1-800-558-0411 or on the web at www.aesham.com.
The digital mode software packages include the following:
PSK31SBW - This is a bare bones program that will get you on the bands using PSK31 that has no frills (i.e. no logging capabilities or other mode selections). This is a very small software program. It could be run off a floppy.
Digipan – This is one of the most popular PSK31 programs. Digipan has a more than adequate logging program to help make your record keeping easier. This is one of the first programs that I operated with and it worked quite well. Very user friendly which is most important especially if you decide to operate during a contest (i.e. Field Day)
Logger – This was one of the first true PSK31 programs that has a more than adequate logging program that tracks most of the award possibilities that one could garner if you were trying for awards from the ARRL. The author of this program added another program (Zakanaka) that came with a user interface that had the appearance of the above-mentioned Digipan. With in the past year the author has changed the Logger/Zakanaka to one program called Logger32b. It includes all of the bells and whistles of Logger/Zakanaka and includes Baudot capability. Zakanaka adds the waterfall capability to Logger PSK31.
Hamscope – This program is a good all around program that will handle most of the modes that you would be interested in operating. It will operate PSK31, QPSK, RTTY, CW, ASCII, PACTOR (receive only) and has some minimal logging capabilities.
MixW – This is the software program that was recently written about in QST. This is probably the preeminent digital program available. There is very little in the digital mode arena that cannot be done with this program. The user interface is very good. It has an excellent logging program and you can even design and print QSL cards. It handles all the chores of contesting quite well. Once you download MixW, you are given a 15 day trial period and then it quits working. The author will send you a file, that you put in the MixW directory. It will unlock the program once you pay the registration fee ($50). This program is well worth the $50 cost. It is my favorite. You can obtain this program through their web site at www.mixw.net
WinPSK – This program handles many of the PSK and logging chores that a digital operator would require.
MMTTY – This is a software program written solely for use on Baudot (RTTY). It has a very good user interface and a so so logging program. This program can be linked (for logging) to the Logger program listed above. MMTTY has a tuning scope for tuning in RTTY signals as part of the user interface. The tuning scope is really neat.
Stream – This is another stand-alone program for operating MFSK-16. Stream does the job for this mode but has some short comings. Most of the other programs have a waterfall at the bottom of the screen to see the signals on the band. In contrast, Stream has a vertical display that shows the signals on the band coming from the right side of the screen. This can make tuning the signals a little more difficult. One other fault with this program is the process required to begin transmitting. You must put your cursor on the bottom windowpane and hit the enter key. The transmitter then comes up. This makes it difficult if you want to enter text in the type ahead buffer before you transmit. I like to put text in the buffer while the other station is sending text to me. Makes it easier to comment about what was said by the other operator.
W1QSL – This program really puts on a show. How about copying 21 PSK31 QSO’s at one time. With this program you have a vertical display that has the signals on the band scrolling from the left to the right. Touch on a signal on the display and a box opens up with the text flowing. Touch another signal and another box opens up, and so on. Open as many as 21 PSK31 windows at once. I’ve told my wife that I can do two or three things at one time, but I will not confess to her that I have trouble reading all of the conversation and remembering what each QSO is about. Whew!
There are many other programs that I have not included. There are far to many to list in this article. Let me try and make it easier for you though, take your browser and point to one of the following URL’s to download most of the programs I listed above or to read more information about the various modes. Try this URL and you will get a chance to hear little snippets of what each of the listed modes above sound like (http://www.wb8nut.com/digital.html). Another URL that you will find interesting and informative is (http://www.aintel.bi.ehu.es/psk31.html). One last website is (http://home.wanadoo.nl/nl9222/digisoft.htm). This website has a very extensive list of programs that can be download for free or might have a small fee it they are shareware.
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