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cactacea | 3 months ago

Expected array gain: ~39.3 dBi / EIRP: ~63.1 dBW

Tx power: 1 W per antenna

Yeah... so free space path loss at legal frequencies for hams this thing can transmit on is ~283dB. Neat idea but consider me skeptical. Having said that I can see some interesting applications for this kind of gear, EME seems overly optimistic though.

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dbcurtis|3 months ago

At those power levels they would have to use some kind of highly error-corrected modulation and coding scheme to provide enough coding gain to overcome the path loss. I agree they are pretty optimistic, but until they detail their modulation scheme, it's hard to tell.

A few years ago I was experimenting with 900 MHz LoRa for a work project -- we had need to communicate a very small data payload from inside elevator cabs, with forgiving latency requirements. So we took a LoRa board to a hotel building 2 city blocks away from our lab and cranked the coding gain up to the max, which gave us about a 1 byte payload every second. Perfectly sufficient for our application. Astoundingly, we had great copy in our lab even when the doors of the elevator cab were closed, inside a building 2 blocks away. I can't remember the power level, 500mW I think, but I may be wrong.

firesteelrain|3 months ago

People use WSJTX software and Q65 mode

Neywiny|3 months ago

It's 1 watt per antenna. They have 240, or 53.8 dbm. So assuming 39.3 and your 283 (which seems to be around what I'm seeing online) that's -283+(39.3*2)+53.8=-150.6 dbm receive power. That should be plenty.

drmpeg|3 months ago

It's theoretically possible.

63.1 dbW = 93.1 dBm (240 watts + 39.3 dB gain)

path loss at 5760 MHz = 283.2 dB (at perigee)

RX gain = 39.3 dB

93.1 - 283.2 + 39.3 = -150.8 dBm

Noise floor at 1.2 dB noise figure and 500 Hz bandwidth = -151.9 dBm

SNR = +1.1 dB (easily detectable by ear with CW).

jacquesm|3 months ago

A few hundred Watt at a minimum would be my first guess.

cactacea|3 months ago

Yeah that is what is used for moonbounce today (if not full legal power - 1500W for US amateurs) but these little panels won't put out anything remotely close to that. Hence my skepticism.