JTDX
| JTDX | |
|---|---|
| Type | Weak-signal digital mode software |
| Derived from | WSJT-X |
| Developed by | A volunteer team led by Igor Chernikov, UA3DJY |
| License | Free, open source (GNU GPL version 3) |
| In use | |
| Platforms | Windows, Linux and macOS |
| Modes | FT8, FT4, JT65, JT9 and T10 |
| Focus | Decoding sensitivity and DXing on crowded HF bands |
| Works with | The same loggers and companion programs as WSJT-X |
JTDX is a free program for the FT8 family of weak-signal digital modes, built from the source code of WSJT-X and changed to suit DX chasers. The name stands for "JT modes for DXing." Its developers concentrated on squeezing more decodes out of a crowded or noisy band and on giving the operator finer control over automatic operation, while dropping some of the specialized modes found in WSJT-X. Because both programs send and receive the same signals, a JTDX station and a WSJT-X station work each other in exactly the same way; the differences are all on the operator's side of the screen.
Background
WSJT-X is open-source software, which means anyone may study, change and redistribute it under the same license. JTDX grew out of that freedom in the mid-2010s, when Igor Chernikov, UA3DJY, began publishing a modified version with changes to the decoders for JT65 and JT9, the main weak-signal modes of the time. Others joined, among them Arvo Järve, ES1JA, and when FT8 arrived in 2017 the team turned most of its attention to it, later adding FT4 as well.
JTDX is developed separately from WSJT-X, on its own schedule, and its version numbers are unrelated to WSJT-X's. It supports the modes most used for HF DXing, FT8, FT4, JT65 and JT9, plus T10, a mode of its own. It does not include WSJT-X modes such as Q65, MSK144 or FST4, so operators interested in meteor scatter, moonbounce or the low-frequency bands still need WSJT-X.
How it differs from WSJT-X
- Decoder options. JTDX offers extra decoding passes and settings that can be switched on or off to suit band conditions and the speed of the computer. On a busy band they can pull out a few more of the weakest or most overlapped signals, at the cost of more processing time.
- Automatic sequencing. The software can step through a contact by itself, and JTDX gives detailed control over which callers it answers, how many times it repeats a message, and when it gives up and moves on.
- Filtering. Decoded messages can be filtered and highlighted by country, continent, call sign and whether a station is new for the operator's award totals, which helps when hundreds of stations are on screen.
- Timing tools. A Sync control lets the operator shift the decoder's timing to match incoming signals when the computer's clock is slightly off, though an accurate clock remains essential for transmitting.
- Fewer contest features. WSJT-X has dedicated message formats for many contests; JTDX has historically put less emphasis on them.
Many operators find JTDX denser and more configurable, with more checkboxes and colors; others prefer the simpler WSJT-X layout. Claims about which decodes better are common on forums, but results depend heavily on settings, conditions and computer speed, and the two are close enough that a fair comparison takes care.
Using JTDX
Setup follows the same pattern as WSJT-X: enter the call sign and grid square, choose the radio for CAT control, select the audio devices, and set the radio to upper sideband on the usual dial frequency, such as 14.074 MHz for FT8 on 20 meters. The station needs a digital mode interface or a radio with built-in USB audio, and the computer clock must be kept within about a second of UTC by time-synchronization software.
JTDX sends the same network messages as WSJT-X, so logging programs, GridTracker and PSK Reporter spotting work with it. It keeps its own settings and files, and it can be installed alongside WSJT-X on the same computer, although only one program can use the radio and sound card at a time.