I would like to keep this thread for discussion related to long-range optimization. I would like to compile a checklist and list of tips in the main post of this thread for everyone to read as a reference. Perhaps we can add something to the wiki.
Please feel free to correct and educate me. Here is my current list of tips:
Opt for 433mhz frequency if it’s allowed by your region. Basic physics dictates that it will have better penetration through buildings, trees, and matter, in general.
Set the transmit power to 20 dBm if allowed in your region.
Get a higher gain antenna for your board. Most of the stock ones shipped with the boards aren’t so great.
Set the channel settings to LongSlow.
Try to get as high as possible with at least one of the nodes to get a better line of sight.
433 is for shipping containers in the US so not an option here. LongSlow is the best tested configuration by a large margin. I would recommend using the default settings for best range and experience.
Use a better antenna. Even the $7 moxon antennas will double or triple your range. One of them on two both ends have shown >100km range on LongSlow.
It is possible to get better than “0.046 kbps 12 / 4096 4/8 31 160dB” for sensitivity, but you’ll need to spend $$ on better crystals for the transmitter.
Tested both 433 and 868. My local city area the 433 is heavily used by cordless weather stations, older mouse/ keyboard, keyfobs, house alarming and more. When using SDR listening 433 you notice there continuous signals in air. 868 is less signal. About the range, i did not notice any improvements against 868 with using a 4dBi base antenna. On 433 using a hamradio base antenna and mobile antenna. The best option in city area is HIGH as possible. Low placed High Gain antennas in City area not give any improvements. The max gain is only available when the antenna is in free open air. The antenna gain lobs are influenced by buildings, trees in surrounding. About gain value there i differ in dBd = gain against dipole antenna and dBi = gain against isotope antenna and best is dBd because dBi is much lower gain. Importend tip: In city area, antenna must go up above all surrounded buildings higher and free space is the magic word on 868 (2 or 3 meters higher give large improve)
You may find the Moxon antenna design here: The Moxon Beam by DK7ZB, moxon yagi, moxon antenna
There’s a free application you can download to calculate dimensions for the 433Mhz band or whatever frequency you need. It’s about 4dB gain over a dipole and a lot more gain than the standard “rubber/plastic” antennas that comes with the board. By the way, those original antennas are quite bad, they’re not even tuned to 433Mhz (~460Mhz instead), pretty crappy…
Are these Moxon antennas unidirectional or omnidirectional? I only plan on having mobile nodes for usage in emergency situations such as in the aftermath of an earthquake or floods.
The Moxon is a unidirectional antenna, but its beam width is pretty large, about 80 degrees @ -3dB. They also have a very good front to back ration, useful if you want to attenuate signals coming from the back (like noise, other nodes, etc).
Regarding the AliExpress antennas, they look like lambda/4 (17cm) and for sure are better than the 4cm ones.
A good omni-directional antenna would be something like this: SA 703-N SA 703-N SA 705-N
There are some disadvantages in using high gain omni-directionals, but usually the benefits are more important.
Unfortunately, you would need to point a Moxon antenna to the direction of interest so it is not really a good idea to mount it on a vehicle.
A better approach would be to use something similar to Diamond SG-M507 antenna (look for clones on Ebay). I have one of those since I’m a Ham operator and usually connect the dual-band radios to it when in mobile (144 & 432 Mhz bands). That antenna works great for the Lora board when in mobile. Within the city, we currently have three fixed nodes at about 10km apart from each other and I haven’t yet found a signal free spot
They might be refereed to as “430Mhz antenna” but they actually cover the 430-440Mhz band entirely.
By the way, those small rubber omni antennas you’ve bought will never have a 4.0dBi as described. Most likely they are 0dBi. Just another misleading Chinese description…
Tbeam + powerbank or other boards in a Gray Hammond IP65 box, drill a hole in the box to fit N- bulkhead, than buy the new SIRIO 868/915 antenna with N-female bulkhead. Put the antenna N-Female bulkhead in to the hole of the hammond box, place this box as high as possible. I will upload a example picture soon. In total made 8x nodes this way, to cover a 6 km circle in city area. I tested the full range or covering while driving in car and later on the bicycle in the city and city borders (family network backup using meshtastic APP).
The same document in table 1 tells us that a standard X-tal can deviate +/- 10 ppm over it’s temperature range.
So if one radio is operated outside on a cold winterday and the other is inside in a hot enclosure the total difference can be 20 ppm worst.
There is also the aging effect of +/- 5 ppm for 5 years and +/- 10 ppm for 10 years
So for worst case after more than 5 years there can be a theoretical difference between sender and receiver of almost 40 ppm !!.
We can assume that the usual LoRa_modems are equipped with a standard X-tal, unless the device-documentation claims it has a TCXO.
Taking this in consideration I conclude that using a BW of 31.25kHz is not a good option for normal LoRa modems except if both/all radio’s in the group are equipped with a TCXO (or if all radio’s operate at the same room-temperature ?).
I may be too pessimistic or even wrong but the numbers in the documentation says so.
I believe that (for non-TCXO modems) only BW of 125, 250 and 500 kHz are reliable on the long term.
Maybe the meshtastic documentation should mention that the mode Long-Fast Bw31_25 can only reliable be used if both or all radio’s in the network have a LoRa-modem with TCXO.
