Delfi-n3Xt transponder to be tested

Delfi-n3Xt Satellite

Delfi-n3Xt Satellite

Delfi Nanosatellite Program Manager, Jasper Bouwmeester PC4JB, has announced tests for Feb 20-21 of the Delfi-n3Xt 435/145 MHz linear transponder for amateur radio SSB/CW communications.

UPDATE February 20, 2014

Dear all,

Today we did a first transponder test. We could hear the beacon, but unfortunately did not hear anything back from our calls. Also we were missing the noise floor of the transponder band. Our hypothesis is that our adjustable LO (Si570) which is mixed with the IF band could not be programmed correctly and hence the pass-band goes outside our filtered band (which is a good thing, because we do not want to transmit on illegal frequencies). This LO is adjustable by I2C communication and should be programmed each time at power up (so each time the transponder mode is activated. We will do two attempts more tomorrow at the morning ground passes and even if that doesn’t help we will keep on trying with different settings. If the situation changes I will update you again.

Best regards,

Jasper, PC4JB

Jasper’s earlier email read:

Dear radio amateurs,

It has been a while since we have provided an update, so it is time to brief you again.

Delfi-n3Xt Status

The satellite is doing fine and is in healthy shape. We are now almost 3 months in orbit and have fulfilled a major part of the primary mission objectives. This means that we are close to a mission success. This does not mean that everything works flawlessly as there are several subsystems with issues. Given the amount of payloads and new technologies, I can only say that this was to be expected and accounted for in the mission. Delfi satellites are developing platforms and Delfi-n3Xt is an in-orbit test facility. The good thing is that issues encountered are not even a final verdict on the subsystems performance. The attitude determination and control subsystem currently is hampered by a high magnetic noise, but might still be tweaked and tune to see if we can get it to work properly. This however takes some time, so we are glad that the satellite seems to be in healthy state and we can take more time to experiment with it.


We are still working on an improved version of DUDe to tackle several issues which we and many of you have discovered and reported. Unfortunately, many of these issues are more difficult to tackle than anticipated and will still take a while before we can release a new solid version of DUDe. One of the main issues is the fact that the software freezes after receiving noise for some time, meaning that DUDe needs to be restarted each time. Attached is a version of DUDe with a dirty fix which resets the PLL every minute. The penalty is that a 1 or 2 frames are lost each minute, so the performance is less than version 5.1. It is however much more convenient for automated ground stations (like our own) and therefore we decided to release this version.


We are going to test the transponder functionality of Delfi-n3Xt this week. I have to be honest that this functionality was implemented last minute on the satellite and was only tested briefly in a non-representative setup. I therefore estimate the chance that it will work at 50/50.

Our first test series will be:

Thursday 20-02-2014 at about 10:50 UT

Friday 21-02-2014 at about 9:50 UT

Friday 21-02-2014 at about 11:25 UT

After a few initial tests, and provided that it works, you are free to use the transponder for communication. We will leave it in this mode for the remainder of the sunlit part of the orbit, so only in Europe and Africa it is possible to use this mode for now. If successful we will turn on the transponder more often and for longer periods of time such that everyone can enjoy it.

[Inverting SSB/CW transponder
• 435.530-435.570 MHz uplink LSB
• 145.880-145.920 MHz downlink USB]

S-band Transmitter

There seems to be a problem on the S-band transmitter causing the current protection to kick in occasionally. Maybe this is due to charging or some other effect, as the board is not protected by The Onboard Computer leaves the transmitter off after several attempts as part of an internal safety mechanism. We can still turn on the S-band transmitter through telecommand, but this will only last for a few passes. Most cases the S-band transmitter will thus be off and it reporting that we have turned it might not be very effective since it might be off again by the time you read the message. If you are still interested to try and receive the beacon signal of the S-band, please check the regular telemetry in DUDe under ‘Status’ ’Satellite Status’ ‘Subsystem Status STX’ to see if it is actually on.

J. (Jasper) Bouwmeester PC4JB, MSc.
Delfi Nanosatellite Program Manager &
Researcher Small Satellite Technology
Chair of Space Systems Engineering
Delft University of Technology

IARU coordinated Delfi-n3Xt frequencies
• 145.870 MHz Telemetry
• 145.930 MHz Telemetry
• 2405.00 MHz High speed data
• Inverting SSB/CW transponder
– 435.530-435.570 MHz uplink LSB
– 145.880-145.920 MHz downlink USB

Telemetry reception


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