• ★ FT8RX - FT8 Decoder
• ★ 2021-03-03
• ★ Questions & Answers

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About FT8RX - FT8 Decoder

Decode FT8 on your phone!

FT8RX is a FT8 decoder for Ham Radio that doesn't require a PC or any other device to function. It records audio input and tries to find and decode FT8 signals each 15 seconds. An internet connection is not needed (except if you wish to synchronize to Internet time via NTP, of course).

Instructions

Timing must be correct in order for FT8 to work. Even though smartphones generally synchronize their clock automatically with the Internet, it still is a small bit off sometimes. For this reason FT8RX has a delay functionality, an internal clock 1 could say, which can be used to further tune the time shift.

You don't need to do anything. Begin the application and it will start looking for FT8 signals. You can check that the application is receiving audio by looking at the sound meter next to the small microphone icon at the top or simply by looking at the waterfall diagram to the bottom.

When the "Decoding" text at the bottom right lights up the application is processing the most latest 15 seconds of audio data. Results are displayed as quickly as possible. If completely nothing could be decoded the decoding light turns off and completely nothing gets displayed.

In case your tablet clock is off by a lot of seconds, test the "NTP SYNC" button. It will connect to a NTP server and adjust FT8RX' internal clock drift. The NTP server has proven to be somewhat unreliable, you might have to test a few times until it is successful.

You can adjust time further to incoming signals by pressing the "-0.1s" and "+0.1s" buttons. If you see that all signals have a positive time drift, you should consider decreasing time drift by pressing "-0.1s" and vice versa.

If you wish to reset FT8RX' clock simply press the "RESET Δt" button. You can see the current offset to your smartphones clock in the lower left corner. If it is 0, FT8RX is basically using your smartphones' clock.

Implementation Notes

The application was developed using the FT8 specification as described by Joe Taylor in an article for the ARRL QEX magazine. Legally, I'm not allowed to check the WSJT-X code for implementation details. Therefore, some features are missing in this app. Please consider the following things before buying this software:

1. The most annoying thing (at least for me) is the absence of the 2500hz SNR dB measurement. I tried to obtain the same results as WSJT-X and gave up on it eventually. Of course, calculating S/N was possible but yielded a various value. To avoid confusion and false reports I left it out entirely.

2. Apparently, lots of very clever tricks. WSJT-X is simply the better decoder. You'll detect a lot less signals with FT8RX. So, even though it could happen that FT8RX found a signal which WSJT-X did not, my tests showed a performance of about 50% (compared to WSJT-X).

3. Some (not so common) FT8 modes are not (yet) supported:

- Type 0.1 DXpedition
- Type 0.3 Field Day
- Type 0.4 Field Day
- Type Five EU VHF

Final Remarks

I'm begin to suggestions and I hope you'll have as much fun with it as I do.

73, Sascha

New Features: Switched to time-c.nist.gov as default time server.

FT8RX - FT8 Decoder Cheats, Hints, Way to Modify, How to Use & How to Win.