Antenna improved range

Default medium range:
Bw125Cr45Sf128 = 0;
///< Bw = 125 kHz, Cr = 4/5, Sf = 128chips/symbol, CRC on.

Fast+short range:
Bw500Cr45Sf128 = 1;
///< Bw = 500 kHz, Cr = 4/5, Sf = 128chips/symbol, CRC on.

Slow+long range:
Bw31_25Cr48Sf512 = 2;
///< Bw = 31.25 kHz, Cr = 4/8, Sf = 512chips/symbol, CRC on.

Slow+long range:
Bw125Cr48Sf4096 = 3;
///< Bw = 125 kHz, Cr = 4/8, Sf = 4096chips/symbol, CRC on.

ModemConfig modem_config = 3

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To be clear, I believe default is the last option in that list not the first option “Default medium range”.

Correct. modem_config = 3 refers to Bw125Cr48Sf4096 = 3;. :slightly_smiling_face:

Edit:
Longer range (SF12:4096chips/symbol) comes off course with longer TX airtime, and consumes more energy as well (TABLE 1, https://www.thethingsnetwork.org/article/how-spreading-factor-affects-lorawan-device-battery-life). The measurement shows that it takes approximately 25 times longer and 25 times more energy to transmit in SF12 compared to SF7.

Airtimes per 20 bytes: https://www.researchgate.net/publication/339153605/figure/tbl2/AS:857195465957376@1581382733097/LoRa-Chirps-SNR-airtime-and-bitrate-according-to-parameter-SF.png

Maximum throughput:

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@geeksville as requested - Work in progress Wiki: https://github.com/meshtastic/Meshtastic-device/wiki/Aerial---antenna-information---selection

All: comments welcome

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Wow that’s really great and way better than what I could have done!

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Thanks @sens8tion, handy info

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Hi, I understand many of these rubber duck antennae assume hand or body to be nearby and give the right SWR with it. It may because they are mostly installed in devices which are on body or in hand (Like Handy radios). Could that be the reason?
Also can check if attaching a pig tail helps.

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The MAX_POWER setting - is it between 0-20 & do we know if it’s linear / logarithmic? has there been any experimentation of what values might start to break in-region rules of power transmission?

I’ve ordered the same. Thank you for sharing your research…

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Good to hear. Please post your findings here.

I achieved 5.16km as the crow flies with NLOS using 0.7.10 stock Meshtastic firmware
and 1/2 Wave 5dbi antenna using the longest range settings in the channel options, using the stock firmware settings. I’m delighted with these results, it proves to me and maybe others that this project could be a viable communications network where no others exist.

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That’s great, impressive range without line of sight. Could you post a link to the aerial you used?

Rigid center-fed 1/2 wave antenna for the 868 MHz frequency band.
SMA connection; 45-90 deg. bendable.
Length: 17 cm
Weight: 20 grams
No ground plane needed and 3dB more gain than a 1/4 wave! (=5dBi)

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Their reply to my “are these numbers real?” was “We have no tests. Only happy customers”.

This is certainly not a perfect test, but better than nothing.
I bought two of these: Amazon 915 mhz Antenna a few weeks ago.

I didn’t know if they were any better than than the included TTGO antennas, so today I used SDRConsole, along with RTL-SDR dongle, to view the signals from my 915 mhz T-Beams. My T-Beam and receiving antennas were only about 6 feet apart. I kept the T-Beam in the same position and switched back and forth between the stock antenna and the NOYITO antenna. The longer NOYITO antenna constantly showed a stronger signal by 2 - 2.5 dBm. This seems reasonable.

Yesterday, I used the Python API to keep re-transmitting a signal for a rough range test. I used the default settings. The transmitting unit was inside my home on the second floor. It was definitely not in a clear area, as it was in front of my desk, attacked to my PC. My house is also surrounded by very many tall trees in my yard, and surrounding heavily wooded areas. I used the new antennas on both units and drove my truck around for the test. The receiving unit was on the dash inside my vehicle. I was able to receive the signal at a little over 1200 meters. I plan to do more testing from better locations later.

I haven’t yet performed the same test with the stock antennas.

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I bough one of these antennas, it covers the 868 and 915 band as well as Wi-Fi. The station is being installed next to Petts Wood Railway Station, in the London Borough of Bromley

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For any of the frequencies used in the TTGO a Bi-Quad antenna will give great gain, though be very directional. With a reflector and a director the gain figures will be at leat 12DBD. ( 16X input level ).
Plenty of people are using them with drones and wifi and finding huge distance increases.

[https://www.changpuak.ch/electronics/bi_quad_antenna_designer.php]

Collinear omnidirectional designs are good, also with plenty of design calculators online.

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Welcome YankeePapa13. I can confirm the link to the antenna calculator gives good working antennas!

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The stock TTGO Tbeam antenna I receive didn’t perform well, So I tore it apart. The plastic sheath that covers the anthem gets hot in a microwave oven only after 10 second of on time. This tell me the sheath absorbs RF. There for attenuate at 2.5ghz. Don’t know if this is the issue at 915mhz.
The antenna is exceptionally short for a 900mhz antenna . the radiating element is only 1 inch and a bit high with a grounded spring rapped around a good deal of that. What is the spring for? Capacitance ? Widen the bandwidth?

On a RF vector meter it has a ok swr near 915mhz. Adding a ground plane to the connector greatly make the antenna worse than without it. The SWR goes to infinity. The impedance nowhere nears a match. And the TX distance decreases to 200 feet away.

I’ve been using Lora since 2016, I know, with a 3dbi mag mount mobile antenna on both sides, I got over 5 miles here in downtown Huntington Beach. On the hill to the beach below, I got about 7 miles.

Short: I need a better antenna.

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I’d really like to know how they compare. I’m looking for some better 915Mhz antennas myself.