Welcome to my digital mode resources page. Digital operation is an ever growing field, and many changes have occurred over the years. I hope you find the information here useful. I will update this page with additional contents and notes as time goes on.
What is needed to work the Ham digital modes
What is digital? A digital signal is a signal that represents a sequence of discrete values. A logic signal is a digital signal with only two possible values, and describes an arbitrary bit stream. Other types of digital signals can represent three-valued logic or higher valued logics. – Wikipedia
Digital modes are a lot of fun and can be very exciting to work. You will see many ads for various digital interfaces, and while they can be very nice, you don’t actually need them for most digital modes. The following equipment should be considered necessary to digital ops.
Minimum necessary
- An HF or VHF radio.
- A computer with a sound card with both microphone input and speaker output.
- An antenna.
- Cables to connect the sound card with the radio.
- Digital mode software.
Nice to have
- A secondary sound card (or digital interface with built in soundcard) that is dedicated to the radio.
- Properly shielded (and perhaps attenuated) audio cables.
Do I need a fancy digital interface?
While interfaces like the SignaLink series, RIGblaster, Navigator, etc. can be very nice to have, most digital modes only require the equipment above. However, if you want to work Clover or Pactor II or higher, you will need the equipment from the respective manufacturers as it is the only way to use those modes.
Years ago, a Terminal Node Controller (TNC) was considered mandatory for digital modes. This was in the heyday of Packet Radio when most computers did not contain sound cards. Many excellent TNCs were produced and are available at Hamfests for around $20 to $50. TNCs operate on a different principle from the sound card interfaces. A TNC is actually an embedded computer with hardware modems and Digital Signal Processing (DSP). Due to the embedded computer, TNCs allow you to leave your radio and TNC on to operate a simple automated “mailbox” or more full featured Bulletin Board System (BBS), without having to have the computer on, or even connected. Certain modes still perform better using a TNC rather than a sound card. However, with modern high-definition sound cards (192kHz sampling rates) this advantage to TNCs is rapidly eroding.
Some available digital interfaces.
| Soundcard Interfaces | TNCs/Modems |
|---|---|
| Navigator by Timewave Technology | PK-232SC+ TNC by Timewave Technology |
| SignaLink USB by Tigertronics | Pactor Modems from SCS |
| SignaLink SL-1+ by Tigertronics | Clover Modems from HAL Communications Corp. |
| RIGblaster from West Mountain Radio | Kantronics TNCs |
| Rig Expert |
I have personally used both the SignaLink USB and SignaLink SL-1+ in the past. Most of my experience was with the SL-1+ and it was very compact and worked well, with the caveat that it did require a separate power source and sound card. The SignaLink USB is USB powered and has a built in sound card like many modern interfaces.
I also own several AEA produced PK-232MBX TNCs (the ancestor of the modern PK-232SC+) as well as the top of AEA line PK-900 TNC (with the soundcard interface upgrade). There is something to be said for the PK-232 line of Terminal Node Controllers. Originally produced by Advanced Electronic Applications, Inc. (AEA), the entire PK-232 line (as well as the PK-900) is now supported by Timewave Technology with a complete line of upgrades that can allow you to take a PK-232 all the way up to the modern PK-232SC+.
There are even systems that eliminate the need for a computer altogether, such as the Nue-PSK digital modem. Some modern radios such as the Elecraft KX2 even handle PSK31 and RTTY internally. QRPworks provides a number of interface boxes for both Elecraft and Yaseu portable HF rigs that even handle logging in addition to providing digital mode displays on the Elecraft line of radios.
Digital modes software
If you aren’t using a radio or modem that has everything built in, then you will need software on your computer to run your sound card (or external sound card interface like the SignaLink or Navigator).
- Digital Master, a part of Ham Radio Deluxe ($$$)
- fldigi – Open source digital mode software
- MixW – the former King of digital software ($$)
- DigiPan – Freeware, but only for PSK31 and PSK63
I have used Digital Master back when it was called DM-780 when Ham Radio Deluxe (HRD) was Freeware. At that time if you had asked me what software to use, I would have unreservedly recommended HRD. I pretty much only used DM-780 and didn’t really use the rest of the HRD suite of software, so when it went paid only I couldn’t justify the purchase price, so I have been looking for new software.
Recently I have been trying fldigi for digital modes. While fldigi has the advantage of being open source and multi-platform (if you are using Linux, it is really the only software for you), I find myself not liking it due to how complex it is. The configuration dialog is vast and has many, many options. fldigi really does try and be everything to everyone, but only if you are using a soundcard. If you happen to have a TNC (or several like me), fldigi really doesn’t cater to you.
Lately I have been playing with MixW, and while the last time I tried it many years ago I was unimpressed and deeply disliked the multiple window approach, I have to say that I am rather liking MixW 3.2. This latest version of MixW allows you to either have floating or docked windows, so you can set it up how you like. MixW also provides the capability for you to integrate your TNC with your soundcard modes, though you do have some work to do in constructing (or finding on-line) the proper macros so that MixW can control your TNC. While I have not yet worked anyone using MixW, I do find myself quite impressed by what I see, and I may just end up paying for it.
Configuring your sound card
Getting the levels correct in your sound card is vitally important to successful decoding of the audio from your radio, as well as ensuring you will not overdrive your transmit audio and transmit a distorted signal. Also as mentioned earlier, make sure you don’t accidentally transmit unintentional signals (such as the Windows startup sound or instant message notifications) by either disabling all OS and program generated sounds, or the easier way is using an external sound card.
Configuring your input levels1
I’ll add some screenshots to this section soon so that it is easier to understand.
In Windows you can open the audio mixer, select your sound device, then properties, select the levels tab, and right click on the slider. This will provide you with the option of using either percentage or decibels for the scale. I recommend you set it to decibels so that you can get an accurate idea of what is occurring with the levels. You will notice that Windows interprets the full slider condition differently between Speakers and Microphones. On speakers a the full slider position represents the 0dB level, and anything less than full is in negative dBs. With Microphones, the full slider position can by anywhere from +10dB to +90dB. This can introduce various artifacts into the audio stream that will cause difficulty with decoding. It is best to get the microphone level as close to 0dB as possible. Again this is much easier to achieve with an external sound card.
Configuring your output levels
The output levels will depend to some degree on your radio. I suggest following your radio or interface manuals suggestions when it comes to setting the output levels. An important thing to understand is that louder is not better. If the levels are too high you will send a distorted signal that will be near impossible to decode as well as cause difficulty to other operators.
Excellent information from around the web
- Computer to Radio Interfacing – You Don’t Need An Expensive Interface! (PDF) – Excellent article by Jim Brown, K9YC that covers some simple methodologies that you can use for connecting your computer to your radio.
Books
Even with the web, sometimes you just need a good book. Here are several that cover the digital modes.
- Nifty E-Z Guide to PSK31 Operation
- Get on the Air with HF Digital
- RTTY/PSK31 for Radio Amateurs – 2nd Edition
I have the older ARRL “HF Digital Handbook” (Fourth Edition – 2007) which appears to no longer be in print. It provided a good overview of the various digital modes, and I imagine the newer ARRL “Get on the Air with HF Digital” should do the same.
More coming soon…
1 Windows soundcard input fix – this page explains some things I’ve been seeing with soundcard interfaces.
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