Guide to using FT4 on satellites

Setup for FT4 on the RS-44 satelliteAMSAT-SM have published a guide to using the popular digital mode FT4 via the amateur radio satellites using SDR-Console software, a SDR receiver and the Icom IC-705 as the transmitter.  We have also had information from Jef ON8NT of the setup that he and Thierry ON2ACO used.

The AMSAT-SM guide covers:

• Step 1 – Setup SDR-Console and IC-705 with correct frequency

• Step 2 – Config WSJT-X

• Step 3 – Start Satellite External Radio in SDR-Console

• Step 4 – Select correct RX frequency in SDR-Console

• Step 5 – Find yourself on the satellite transponder

• Step 6 – Start calling CQ

• How to use a 2nd instance of WSJT-X for RX of your own FT4 signal

Read the guide at https://www.amsat.se/2021/08/15/ft4-via-satellite-with-sdr-console-and-ic-705/

This is a short video of FT-4 communication via satellite AO-73 with SDR-Console V3.1 and Icom IC-705. It is a part of a guide that will be published later on AMSAT-SM web https://www.amsat.se/

In the first part you will see the first screen with SDR-Console with Airspy Mini as receiver, audio is piped to WSJT-X. You will also see SDR-Console handle the TX Doppler correction for the IC-705 via “External radio”.

In the second part you will see the second screen with WSJT-X connected to IC-705. The output was only one (1) to two (2) watts! You can see that WSJT-X is reading the Doppler corrected frequency. You will also see SDR-Console satellite tracking and PstRotator controlling the SPID RAS rotor.

Watch FT4 via AO-73 with SDR-Console and Icom IC-705

Thierry ON2ACO and Jef ON8NT use the ICOM IC-9700 for FT4 on the satellites.

They used the video from NU1U on YouTube which gives a good step by step ‘how-to’.

Watch IC-9700 using SatPC32 and WSJT-X

Instead of SatPC32 they used the S.A.T. controller from http://csntechnologies.net/sat

For configuring the RX instance from WSJT-X, also the article from GM4FVM on using multiple instance was very helpful in setting up the soundcard properly in WSJT-X !
See https://gm4fvm.blogspot.com/2021/02/multiple-instances-of-wsjt-x-using-more.html

Caution Urged in Using High Duty Cycle Digital Modes via Satellite

Amateur Radio Satellite FO-29

Amateur Radio Satellite FO-29

A report in ANS-288 discussed an experiment operating with the WSJT-X FT8 digital mode via satellite. Satellite operators have gained more experience with this mode over this past week.

As a result of on-the-air observation other satellite users planning to try FT8 or MSK144 modes via satellite are encouraged use caution using these modes and possibly avoid their use completely in light of problems.

Dave, KG5CCI wrote, “He noticed a very hard time getting into the transponder. The pass was nearly overhead, and the 3w-4w that is normally sufficient was barely cutting it. I also noticed it was ‘up and down’ alot, whereas some moments it was easy to get in, then it would be nearly impossible. There were also pockets of ‘noise’ all over the transponder, that sounded somewhat digital, but I just couldn’t place them.” Further investigation revealed that an MSK144 signal in the transponder passband was causing the problems.

Matthew, NJ4Y noted, “Experimentation isn’t the problem, too much power is. It’s bad enough on SSB, worse with CW, and killer on constant duty cycle modes like FT8.”

To gain a full understanding of the situation readers are encouraged to follow the amsat-bb message thread which can be accessed at http://www.amsat.org/pipermail/amsat-bb/2017-October/064896.html

Source: AMSAT News Service http://www.amsat.org/mailman/listinfo/ans