Another part of Stars Song project will consist in sending and receiving radio signals in telegraphy or telephony (Single Side Band) or digital signals toward the Moon. CAMRAS WebSDR in diffusing such radio signals sent by radioamateurs and reflected by the Moon. La Villette radiotelescope antenna should be equipped with a source cavity adapted to Earth-Moon-Earth (EME) frequency band around 1296 MHz. We are thinking of using digital transceiver (Transmitter – Receiver) Lime SDR, a device that has been selected by European Space Agency.
All these operations are achieved by capturing radiowaves signals using a Software Defined Radio (SDR) receiver. Receiver is driven by a software driver that is presently under development by INDI developers. Using INDI API for both sky objects targetting and recording will simplify development of both parts of our project, radioastronomy and hamradio communications.
Present SDR market has a few TRX (transmitter and receiver) offers such as LimeSDR. The choice of TRX model for EME (Earth Moon Earth, EME) is not yet fixed. LimeSDR mini will soon be tested. A driver for LimeSDR is still under beta test in INDI library.
For those who are not afraid by physics and mathematical formulas a thesis about theory and practice of 1296 MHz Earth – Moon – Earth communication system can be downloaded from here.
Here is the thesis abstract :
« The task of designing, building and characterizing an Earth–Moon–Earth(EME) communication system in the 1296 MHz amateur radio band hasbeen successfully accomplished. Using the radar equation and thermal noisetheory, in conjunction with measured and estimated system parameters, thelunar echo signal to noise ratio (SNR) has been estimated 5.4+1.2/−1.6dB (2σ) in a 100 Hz bandwidth. The results of empirical long-term averaged SNRmeasurements are within the boundaries of this estimate, thus adding toits validity. Additionally, measurements of the libration-induced Dopplerspread of the lunar echoes show good agreement with theoretical predictions.Further experiments should be conducted however, in order to asses therepeatability of the results. Improvements to the system and measurementmethods should also be considered. The report focuses on both theory andpractice and apart from the above, additional attention is given to the topicof low noise figure (NF) measurements due to the systemic importance ofthe LNA NF parameter. »