JT65 Digital Mode

Antony M0IFA

JT65• JT65 is a sent as a set of 65 tones (frequencies)

• Designed for EME (Earth-Moon-Earth) weak signal comms

• Very brief QSOs, special code messages, 63 symbols

• Plus plain text messages with max 13 characters

Signals• 65 spot frequencies

• Audio out, USB, - 1270.5 Hz Sync and 63 message symbols at +2.69Hz x (n+2)

• 126 time intervals of 327ms Msg takes up to 47.8s

• Start ALWAYS 0 to1sec after UTC minute

Sync0 Msg2-65

47.8s

Tim

e

Freq

Coding• Uses ASCII input (UC + 0-9)

• Message compressed and error correction bits added - Using Reed-Solomon algorithm (as on CDROMs, HDD..)

• Pseudo-random Sync Vector interspersed

• Total sent is 126 symbols (63 msg + 63 sync)

WSJT-X Rx

JT65-HF Rx

Arduino &

AD9850 Tx

The AD9850 module

Control signals- D7 DATA - WCLK - FQUP - REST

RF out

125MHz xtal

Transmit

• PC running Arduino ID - Serial Monitor window

• Arduino UNO running JT65_ADS_TEXT sketch

• RTC for accurate timeCalibrated usingRTC_SET sketch

• AD9850 generatingRF output

Receiver

• Arduino runningSDR_ELEKTOR sketch

• Elektor SDR shield • Analog-Digital Audio

convertor • MacBook running

HDSDR and JT65-HF

AD9850 TXWaiting for minute Sending message

Enter msg on PC

Display on LCD

Wait for minute Send on Freq

HDSDRElektor SDR

centre frequency set to 7100kHz

Loopback audio to JT65-HF

JT65 TX 7076000 RX Dial 7074830

JT65-HF RX

Elektor SDR

AD9850 & RTC

RF Meter

Demo hopefully

SDR VFO/JT65 RF METER