4 ms·

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 transm

by cactacea 11mo 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.

jacquesm 11mo ago
A few hundred Watt at a minimum would be my first guess.
- cactacea 11mo 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.
  - deleted 11mo ago
    [deleted]
  - mschuster91 11mo ago
    Y'all can run at 1500W? Here in Germany the legal limit (depending on band of course) is 750W.
dbcurtis 11mo 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 11mo ago
  People use WSJTX software and Q65 mode
- mystraline 11mo ago
  This person has a full SDR LoRa transceiver stack and the meshtastic client code. https://gitlab.com/crankylinuxuser/meshtastic_sdr https://gitlab.com/crankylinuxuser/meshtastic_sdr
drmpeg 11mo 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).
Neywiny 11mo 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.

jacquesm 11mo ago

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

cactacea 11mo 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.
- deleted 11mo ago
  [deleted]
- mschuster91 11mo ago
  Y'all can run at 1500W? Here in Germany the legal limit (depending on band of course) is 750W.

dbcurtis 11mo 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 11mo ago
People use WSJTX software and Q65 mode
mystraline 11mo ago
This person has a full SDR LoRa transceiver stack and the meshtastic client code. https://gitlab.com/crankylinuxuser/meshtastic_sdr https://gitlab.com/crankylinuxuser/meshtastic_sdr

drmpeg 11mo 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).

Neywiny 11mo 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.