JT65

An introduction to JT65: A weak‐signal high frequency digital mode

WSJT modes of di it l digital communi ti ca on were ori i ll g na y dl d eve oped by Joe T l ay or (K1JT) in 2001 as a method of communicating via radio in conditions where other modes would not be intelligible. These so called WSPR (weak signal propagation) modes use sophisticated DSP (digital signal processing) methods to decode signals which are not audible as they exist below the noise floor. 2 JT65:

Overview

• Dl d eve oped in 2003 for EME and T hi ropospheric propagation modes

• It dd n en ed to be a QRP mode in HF – QRO operation wreaks havoc around the world!

• Able to d d eco e si l gna s many dB b l e ow noise floor

• Intelligence sent using MFSK with 65 tones

• Each transaction takes 1 minute – Transmit duration is 47 seconds • Forward error correction done via RS ( d Ree ‐Sol ) omon 3 JT65: Requirements

• C t ompu er cl k oc s must be synch id ron zed – The use of an NTP (network) time server such as time nrc ca time.nrc.ca is highly recommended recommended – Any operating system can be set to synchronize with a central time server – When using JT65, ensure your time is correct as a difference of 10s may prevent operation • T i ransm t on ei ht er even or odd minutes – Traditionally, Region 2 transmits on even minutes – In HF b d an s, the convention is generally f ll d o owe b t u if conditions require, it is common to switch to odd frames

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