Joe Taylor K1JT has announced a new digital mode, FT4, which is 2.5 times faster than FT8
FT4 is an experimental digital mode designed specifically for radio contesting. Like FT8, it uses fixed-length transmissions, structured messages with formats optimized for minimal QSOs, and strong forward error correction. T/R sequences are 6 seconds long, so FT4 is 2.5 × faster than FT8 and about the same speed as RTTY for radio contesting.
FT4 can work with signals 10 dB weaker than needed for RTTY, while using much less bandwidth.
FT4 message formats are the same as those in FT8 and encoded with the same (174,91) low-density parity check code. Transmissions last for 4.48 s, compared to 12.64 s for FT8. Modulation uses 4-tone frequency-shift keying at approximately 23.4 baud, with tones separated by the baud rate. The occupied bandwidth (that containing 99% of transmitted power) is 90 Hz
Adam Rong BD6CR has designed a simple DSB Transceiver for FT8. Crystals are available for 7.074 MHz. and 14.070 MHz (which can be “pulled” with a trimmer to 14.074 MHz).
Using only 4 Transistors, 2 IC’s, 3 Toroids, 5 Diodes/LED’s and a handful of resistors and capacitors this one watt wonder will get you on the air in no time.
Click to enlarge.
One could build this on Perfboard (see above), or use Ugly/Manhattan style construction. There are no plans for a circuit board.
Adam posted this on groups.io crkit:
“I built this 7074 DSB 1-watt radio and made 6 FT8 QSO with JA stations in 15 mins last weekend. It is fun to operate by switching PTT manually to keep it simple and lower current consumption.”
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