W7GJ

CHECKLIST & TIPS FOR SUCCESSFUL
 50 MHZ EME CONTACTS USING JT44 MODE

 

INTRODUCTION

STATION REQUIREMENTS

JT44 ECHO MODE
JT44 EME CALC

SCHEDULING

JT44 SETUP

W1JJ Setup

ACTUAL JT44 OPERATION

K7BV on Spectran
Above image shows a weak SPECTRAN trace from K7BV, approximately 10 dB above the background noise.  This clearly shows where the signal is, and where the narrow JT44 "FREEZE" filter safely can be set.  The weak signal observed above did not decode in JT44.
Use of a wide FREEZE filter on W1JJ
The above image shows use of a wide FREEZE filter with a TOL of 400 Hz.

Narrow FREEZE filter on K7BV
The above image shows a relatively narrow FREEZE filter with a TOL of 100 Hz on a weak "SYNC 1, -30 dB" message.  Without the FREEZE filter, this message registered as a very weak "SYNC 0, -33 dB" , with no decode.  Note that the narrow FREEZE filter not only increased the SYNC level, but also permitted display of the signal reports in the character averages columns!  The proper frequency to set the freeze filter was determined from previous transmissions, and also by watching the signal with SPECTRAN on a separate computer.

Folded callsigns from W1JJ
The above image shows a message that decoded, but apparently did not result by itself in clean callsigns.  However, when the message was folded by using the "FOLD" button (possible only when both halves of the each message are identical), the callsigns are solid copy!
Reports from K7BV in the CHARACTER AVERAGE columns
The above image shows "OO O" in the character columns.  Although this is shown as a very weak "SYNC 1, -30 dB" signal. the reports are very clearly shown in the character average columns (partly due to the fact that the SYNC was set to zero and a narrow FREEZE filter was being used).   Please do not be confused by the DT (which should be around 3) displayed here (the transmitting station's computer clock was 4 seconds too fast)

REFERENCES

CONCLUSION

This page last updated on October 21, 2003