My son KJ7NLL is working to contact the ISS using an antenna we built together, and we were wondering the approximate minimum transmission power to reach the ISS. If I understand correctly (and correct me if I'm wrong), roughly speaking, we need to solve for tx_power from the following equation (in dB) to estimate the minimum tx_power:
- tx_power - feedline_loss + tx_antenna_gain - path_loss + rx_antenna_gain + (-rx_sensitivity) = 0
The Kenwood TM-D710GA onboard the ISS has a sensitivity of 0.16uV (which we think is -122dBm if we did the math right). Our 2m helical antenna gain is ~13dB and path loss to the ISS when directly overhead is ~127dB (of course, we need more than that when near the horizon, but not sure what that distance would be).
The ISS has a series of "WA" antennas, but we have not found the gain specs.
- What are the gain specs (and patterns?) for the ISS U/V antennas?
- Is our math right?
These are the ISS U/V Amateur Radio antennae pictured from this PDF: