A follow-up to our previous news on the DELFI-N3XT transponder test was received via e-mail today:
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.