Open-source communications by bouncing signals off the Moon
1–10 of 88 posts
Re: Open-source communications by bouncing signals off the Moon
#2I started reading thinking it was impossible but it has been done with other devices https://en.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93Ear...
Re: Open-source communications by bouncing signals off the Moon
#3Expected 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.
Re: Open-source communications by bouncing signals off the Moon
#4I started reading thinking it was impossible but it has been done with other devices https://en.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93Ear...
Not impossible, just extremely difficult. I'm a ham and getting some contacts over moonbounce is a personal goal of mine. Historically this kind of thing has required some pretty large antenna arrays and very high power though:
https://hamradio.engineering/eme-moonbounce-bouncing-signals...
http://www.g4ztr.co.uk/app/download/13284489/RaCcom_Feb14+EM...
http://www.g4ztr.co.uk/app/download/13300096/Radcom_Mar144+E...
Re: Open-source communications by bouncing signals off the Moon
#5Latency?
Re: Open-source communications by bouncing signals off the Moon
#6Expected 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.
A few hundred Watt at a minimum would be my first guess.
Re: Open-source communications by bouncing signals off the Moon
#7Latency?
1 sec up and 1 sec down... more or less. Speed of light and distance to the moon, two times.... roughly.
Re: Open-source communications by bouncing signals off the Moon
#8Expected 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.
A few hundred Watt at a minimum would be my first guess.
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.
Re: Open-source communications by bouncing signals off the Moon
#9I started reading thinking it was impossible but it has been done with other devices https://en.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93Ear...
Not impossible, just extremely difficult. I'm a ham and getting some contacts over moonbounce is a personal goal of mine. Historically this kind of thing has required some pretty large antenna arrays and very high power though: https://hamradio.engineering/eme-moonbounce-bouncing-signals... http://www.g4ztr.co.uk/app/download/13284489/RaCcom_Feb14+EM... http://www.g4ztr.co.uk/app/download/13300096/Radcom_Mar144+E...
Isn't there a moon bounce mode in WSJT (or one of those digital modes) that provides enough coding gain that 100W and a single large Yagi is enough? I seem to recall hearing something like that... but, yeah, on CW a monster antenna and the legal limit of 1500W seems to be the median system.
A long time ago I started collecting parts for a 432MHz EME system. Life got in the way and I never built it out. Good luck with your endeavor!
Re: Open-source communications by bouncing signals off the Moon
#10Expected 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.
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.