Ground Sphere CubeSat Ground Station

We are about to begin formal testing of prototype 1. In preparation for this testing we need to finish documenting our test procedures and conduct any required analysis to support those tests. For prototype 1, the key tests are covered in the Test 1.1.2 Instructions. These tests include a lab test to confirm the completed ground station can receive signals at 915 MHz as expected, a field test to simulate from orbit communications using long distance signals on Earth plus attenuation, and a from orbit test (if possible). The first two tests require analysis to predict the performance and/or determine test conditions (for example how much attenuation is required during the field test). Note, the Preliminary Design documentation should include all required values for the ground station and CubeSat radios/antennas.

Wilton has volunteered to provide some of this analysis. In particular, he is working on determining the predicted performance of the ground station during the lab test so we can compare the actual performance and determine is the system is working as designed. Below are his comments (and attached is his updated link budget).

I added some new columns to the Link Budget for calculating power setting for the test transmitter to test/simulate similar signals on the ground station.

I assumed that the test transmitter would be an omni-directional antenna, but the power needed to transmit is pretty small so perhaps using a directional antenna but not aiming it directly at the ground station may make a better test signal. I know the transmitter can go down to -30dBm but I don't think the side channels are supressed as well so operating the transmitter in the lowest power setting has the worst/noisiest setting as well so it won't be the cleanest signal.

I attached the spreadsheet to this email.

Will

Wilton or Aaron, can either of you walk me through these calculations to help me understand how we go from the attached link budget to an expected value in SeeDeR during the lab test? Also, is it possible to adjust the transmit power on the test radio and confirm we get predicted signal values for say 3 signal strengths?