Progress report 3 October 2005



KiwiSAT FM Transponder on Test


As part of the development for KiwiSAT a trial unit FM U/V transponder was constructed and placed in the vacuum chamber at Massey University in Auckland. During these tests the unit failed with the Beacon becoming intermittent and the transmitter behaving strangely.


For further investigation the system was returned to Christchurch where tests revealed that the crystal oscillator had become rather unstable being extremely heat sensitive, subject to microphonics, and susceptible to minor circuit changes such as the slightest movement of any oscillator components.


The crystal was replaced and performance returned to normal. In pursuing this failure the crystal can was opened and a significant portion of the crystal wafer was found to be missing. (See picture)


A new crystal for tests has been obtained and the transponder will be on the air in Christchurch with a transmit frequency 144.584MHz. If you hear its beacon "ZL6SAT KIWISAT PROTYPE", try transmitting on the receiver input frequency of 435.925 MHz narrowband FM. There is a short kick-back when your transmission ceases.


Squelch disables the Beacon audio input and allows the receive audio to modulate the transmitter.


To procure a space-qualified crystal may take several weeks or months. In the meantime tests will continue on the U/V test frequencies of 435.925MHz input and 144.584MHz output.



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Last updated 02/10/2005