3 ms·

Using 900 MHz means you only get line of sight which means you need height above terrain. In a disaster maybe you can get this without paying anyone any money s

Using 900 MHz means you only get line of sight which means you need height above terrain. In a disaster maybe you can get this without paying anyone any money so this might be feasible. Using HF would be better in almost all ways except size though.

vvanders 7y ago
900Mhz will punch through some stuff and the spread spectrum chrip Lora uses will do non-LoS[1] under some conditions. The bigger issue is to get that capability Lora is a really low bit-rate(on the order of bits-per-second) and polled instead of ad-hoc. [1] https://arstechnica.com/gadgets/2019/10/lostik-usb-lora-radios/ https://arstechnica.com/gadgets/2019/10/lostik-usb-lora-radi...
- superkuh 7y ago
  Yeah, I heard the same thing. So now I own a bunch of 900 MHz transceivers, telemetry dongles, and equipment. I don't think it deserves the good rep it gets. It may punch to the other side of the house or do okay through some pine trees point-to-point but at the slightest hill or gentle dip it's done. It's best to treat it like a microwave link. And for a microwave link it has a pretty significant fresnel zone.
jcims 7y ago
I always thought it would be cool to make a little portable kit to fly an antenna/relay in case of emergency. The practical solution would probably be a parafoil, but a chemical hydrogen generator and balloon would be way more fun.
- superkuh 7y ago
  Some way to get height above terrain is required. One of the more game changing ways I've heard about is using specially shaped TEM mode launchers with thin single wires to transmit RF power up to a hovering quadcopter to be rectified. Glenn Elmore has published some articles about these surface wave transmission lines in the amateur radio magazine QEX (mirrors at: http://www.sonic.net/~n6gn/ http://www.sonic.net/~n6gn/) and documented some 50w power tests on his youtube channel, https://www.youtube.com/user/n6gnSWTL https://www.youtube.com/user/n6gnSWTL I implemented a pair of these launchers designed for my 900 MHz "wifi" setup using a ubiquiti 900 MHz tranceiver running broadband hamnet firmware. It seemed to carry the signal to the antenna as well as a similar length of RG-6 coax. http://erewhon.superkuh.com/swtl_launcher_complete.jpg http://erewhon.superkuh.com/swtl_launcher_complete.jpg It was a little fragile and the connection to the SMA connector broke on one. Some day I need to resolder it and put one end up in a tree. Glenn's 2.5d metallized paper designs look much easier to build and more robust.

vvanders 7y ago

900Mhz will punch through some stuff and the spread spectrum chrip Lora uses will do non-LoS[1] under some conditions. The bigger issue is to get that capability Lora is a really low bit-rate(on the order of bits-per-second) and polled instead of ad-hoc. [1] https://arstechnica.com/gadgets/2019/10/lostik-usb-lora-radios/ https://arstechnica.com/gadgets/2019/10/lostik-usb-lora-radi...

superkuh 7y ago
Yeah, I heard the same thing. So now I own a bunch of 900 MHz transceivers, telemetry dongles, and equipment. I don't think it deserves the good rep it gets. It may punch to the other side of the house or do okay through some pine trees point-to-point but at the slightest hill or gentle dip it's done. It's best to treat it like a microwave link. And for a microwave link it has a pretty significant fresnel zone.

jcims 7y ago

I always thought it would be cool to make a little portable kit to fly an antenna/relay in case of emergency. The practical solution would probably be a parafoil, but a chemical hydrogen generator and balloon would be way more fun.

superkuh 7y ago
Some way to get height above terrain is required. One of the more game changing ways I've heard about is using specially shaped TEM mode launchers with thin single wires to transmit RF power up to a hovering quadcopter to be rectified. Glenn Elmore has published some articles about these surface wave transmission lines in the amateur radio magazine QEX (mirrors at: http://www.sonic.net/~n6gn/ http://www.sonic.net/~n6gn/) and documented some 50w power tests on his youtube channel, https://www.youtube.com/user/n6gnSWTL https://www.youtube.com/user/n6gnSWTL I implemented a pair of these launchers designed for my 900 MHz "wifi" setup using a ubiquiti 900 MHz tranceiver running broadband hamnet firmware. It seemed to carry the signal to the antenna as well as a similar length of RG-6 coax. http://erewhon.superkuh.com/swtl_launcher_complete.jpg http://erewhon.superkuh.com/swtl_launcher_complete.jpg It was a little fragile and the connection to the SMA connector broke on one. Some day I need to resolder it and put one end up in a tree. Glenn's 2.5d metallized paper designs look much easier to build and more robust.