Required power for communication on Lunar distances.

Igor - Assume MW7IC2425 25WT with narrow band PAE 40% will transmit 10WT (40dBm).Assume nRF24L01 sensitivity -85dBm (at 1Mbps). Assume cascade 3 LNA amplifiers (SKY67014-396LF) with noise 4dB,  gain 36Db total. On distance 400000km path Loss 212 dB on 2450 MHz, all this will require on both side antennas with 28dBi gain to get -80dBm RX power. Enough to work with nRF24L01’s sensitivity -85dBm and margin for a noise 85-80 = 5dB. Using  different LNA amplifiers (MC13850EPR2) will give 6dB noise and 39 gain, outcome in this case -77dBm with margin for noise 85-77 = 8dB. Pretty tight.

To test on Cubesat transmitter == 0.5WT transmit (27dBm), distance 400km path loss 152 dB, symmetrical antennas with 8dBi gain will give in that case -70dBm RX power. That is a goal for test flight.

For first test on ground, transmitter has to be stripped from power amplifier with LNA cascade 26-29dB and direct 1mWt (0dBm) output to same antennas (8dBi) as for Cubesat to get same -71dBm power on RX. Distance has to be 20 km (path loss 126dB). Direct distance  = Cyprus – SFU hill ==25,  Grouse Mt. – SFU hill == 15km, and Mt. Seymour – SFU == 9 km.

For second test on ground, transmitter with 0.1WT (20dBm) and same antennas require 2km (path loss 106dB) distance for same -70dBm RX. In this case LNA amplifiers hast to be removed, or put into by-pass mode.

To calibrate 8dBi ‘s antennas,  power amplifier and LNA has to be both removed and -70dBm RX achieved on distance 200m. Adjusting antennas from original can be done by reducing amount of turn on helix. Perfect spot for this - is my window on 14th floor and a BC place near steam's plant.

Reduced size helical shows 10cm length with 15 dBi, and on 40cm around 28dBi (today it is only speculations). To confirm that needs to test on distance 200m antennas with 1/3 of turns. And after  that conformation has to be done on regular helix 8cm (3 turns).

For testing 0.5-1WT PA pretty good is glass windows in my building – glass reduces signal – measuring distance with calibrated 8bDi antenna helix allows to calculate path loss over glass (LNA has to be bypassed) estimation for today is 15-25dB. Distance around 0.5km – 0.7km on spot of Olympic village can be used to test full system. To get -69dBm RX power needs to path loss 112 dB (4km) on 0.5WT or 115dB (5.6km) loss for 1WT.

Useful link for this (instead all formulas searches, implementation inside calc and etc.) - http://www.changpuak.ch/electronics/calc_10.php


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