If I know the exact location/direction of a person I wish to connect to via a Meshtastic device 40km away, what antenna type/size would be required if I need it to be portable, i.e. I can fit it into a backpack?
When I was younger, working at the MIT ATR (antenna test range) I was able to chat with John D. Kraus (he discovered the Helix antenna) and learned the details of how he accidentally made the discovery. It's in one of his books. Anyways, I was able to build and test the gain of small (Hydrogen Line) 1420 MHz Helix antennas to use as the feed point on an old TVRO 10' dish. That I used at home for Radio Astronomy and some SETI hobby stuff. I wanted to use a Helix feed because I wanted to reduce the heavy interference from GPS satellites that use Right Hand Circular Polarized, (RHCP). I actually made RHCP feeds, because the signal polarization is Reversed when it bounces back off the dish. (like looking in a mirror) So my rig was great for hearing LHCP but the RHCP GPS birds were very weak (-20db down). IIRC, there was a 3db loss with Vertical or Horizontally polarized signals. I was still able to hear SSB EME from South America when the Moon was up high. I'll be interested to see what a Helix can do on the 906 MHz US LoRa channel20. I have done a little testing with a 10 element Yagi and was able to get some fast TraceRoute returns from 3.1 miles, over a very poor path. The Yagi works a little better than my Reference (gain) Dipole. I like the idea of using high gain CP antennas on Nodes that are set up as long-range Repeater links between towns or remote locations.
Great experience, I appreciate a lot you're sharing this. I guess the circular polarization is one of the big advantages of an helix versus a Yagi antenna to eliminate unwanted signal reflections and interferences. I used quite extensively helix antennas for drone video in the 5.8Ghz band. At such frequencies helix antennas are quite compact which makes them very useable. Seeing the relatively much bigger size of an helix for the meshtastic band, as you say, it can practically be used only for permanent fixed nodes.
@@PoweredMeshtasticEurope A small 8-turn Helix on 906.875 MHz would not be very large. It might a be good Hand-held rig for finding lost Nodes, or checking site locations for link suitability. In the USA, small handheld antennas are sometimes used in a "Fox Hunt" to find hidden radios. I believe most of the animal tracker RDF systems these days still use Yagi beams. Which are not really safe to use close quarters, due to the Eye hazard. Which makes the Short Helix more desirable in my opinion. IMHO, after installing many a UHF Yagi on towers. Yeah, I still climb my little 30 foot Ham tower (ROHN 25G) at the age of 78! One more good reason to use CP is the low Loss when connecting with a Vertical or Horizontal polarized antenna, it's only 3dB. However, if you are using a Vertical antenna, to connect with an antenna that fell over and is now Horizontal, you could see about a 20 dB loss. In some cases, that signal would be undetectable. GPS satellites use RHCP, which means the tiny antenna in your Node can be sitting at almost any angle and still work just fine.
I did not use a calculator for the helix dimensionning (because as said in the video, I found them incorrect or badly programmed so fields would not update or they would take fixed decisions on certain parameters that I wanted the freedom to change) so I made my own excel sheet with formulas and best practices gathered online from various sources. I can share the excel file if needed
If I know the exact location/direction of a person I wish to connect to via a Meshtastic device 40km away, what antenna type/size would be required if I need it to be portable, i.e. I can fit it into a backpack?
When I was younger, working at the MIT ATR (antenna test range)
I was able to chat with John D. Kraus (he discovered the Helix antenna) and learned the details of how he accidentally made the discovery. It's in one of his books.
Anyways, I was able to build and test the gain of small (Hydrogen Line) 1420 MHz Helix antennas to use as the feed point on an old TVRO 10' dish. That I used at home for Radio Astronomy and some SETI hobby stuff.
I wanted to use a Helix feed because I wanted to reduce the heavy interference from GPS satellites that use Right Hand Circular Polarized, (RHCP).
I actually made RHCP feeds, because the signal polarization is Reversed when it bounces back off the dish. (like looking in a mirror) So my rig was great for hearing LHCP but the RHCP GPS birds were very weak (-20db down). IIRC, there was a 3db loss with Vertical or Horizontally polarized signals. I was still able to hear SSB EME from South America when the Moon was up high.
I'll be interested to see what a Helix can do on the 906 MHz US LoRa channel20.
I have done a little testing with a 10 element Yagi and was able to get some fast TraceRoute returns from 3.1 miles, over a very poor path. The Yagi works a little better than my Reference (gain) Dipole.
I like the idea of using high gain CP antennas on Nodes that are set up as long-range Repeater links between towns or remote locations.
Great experience, I appreciate a lot you're sharing this. I guess the circular polarization is one of the big advantages of an helix versus a Yagi antenna to eliminate unwanted signal reflections and interferences. I used quite extensively helix antennas for drone video in the 5.8Ghz band. At such frequencies helix antennas are quite compact which makes them very useable. Seeing the relatively much bigger size of an helix for the meshtastic band, as you say, it can practically be used only for permanent fixed nodes.
@@PoweredMeshtasticEurope A small 8-turn Helix on 906.875 MHz would not be very large. It might a be good Hand-held rig for finding lost Nodes, or checking site locations for link suitability.
In the USA, small handheld antennas are sometimes used in a "Fox Hunt" to find hidden radios.
I believe most of the animal tracker RDF systems these days still use Yagi beams. Which are not really safe to use close quarters, due to the Eye hazard.
Which makes the Short Helix more desirable in my opinion.
IMHO, after installing many a UHF Yagi on towers.
Yeah, I still climb my little 30 foot Ham tower (ROHN 25G) at the age of 78!
One more good reason to use CP is the low Loss when connecting with a Vertical or Horizontal polarized antenna, it's only 3dB.
However, if you are using a Vertical antenna, to connect with an antenna that fell over and is now Horizontal, you could see about a 20 dB loss. In some cases, that signal would be undetectable.
GPS satellites use RHCP, which means the tiny antenna in your Node can be sitting at almost any angle and still work just fine.
Merci,
Je suis impatient de voir la suite.
merci
Moi aussi
Link to calculator?
I did not use a calculator for the helix dimensionning (because as said in the video, I found them incorrect or badly programmed so fields would not update or they would take fixed decisions on certain parameters that I wanted the freedom to change) so I made my own excel sheet with formulas and best practices gathered online from various sources. I can share the excel file if needed
@@PoweredMeshtasticEurope Thank you for the great information in this video as well as part 2. Any chance I can also get the spreadsheet?
Great!!!
Thx