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157 lines
7.5 KiB
Plaintext
157 lines
7.5 KiB
Plaintext
---
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id: radio-settings
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title: Radio Settings
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slug: /overview/radio-settings
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sidebar_label: Radio Settings
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sidebar_position: 1
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---
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:::info
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Meshtastic is **not** LoRaWAN, nor TTN (TheThingsNetwork). Meshtastic uses the full spectrum frequency range designated to LoRa technology per region. This allows for several hundred possible frequency channels in the US region alone.
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:::
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See [this site](https://www.rfwireless-world.com/Tutorials/LoRa-channels-list.html) for more information.
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## Europe Frequency Bands
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Power limits will generally be lifted in the software if `is_licensed` is set to `true` [HAM Mode](/docs/faq#amateur-radio-ham))
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### 433 MHz
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The maximum power allowed for Europe is +14dBm ERP ([Effective Radiated Power](https://en.wikipedia.org/wiki/Effective_radiated_power)).
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The band range is from 433 to 434 MHz.
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There are eight channels defined with a 0.2 MHz gap between them. Channel zero starts at 433.175 MHz
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### 868 MHz (ISM Band)
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The maximum power allowed for Europe is +27Bm ERP ([Effective Radiated Power](https://en.wikipedia.org/wiki/Effective_radiated_power)).
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The band range is from 863 to 870 MHz.
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There are eight channels defined with a 0.3 MHz gap between them. Channel zero starts at 865.20 MHz.
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|Channel Number| Center Frequency|
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|:---:|:---:|
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| 10 |865.20 MHz|
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| 11 |865.50 MHz|
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| 12 |865.80 MHz|
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| 13 |866.10 MHz|
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| 14 |866.40 MHz|
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| 15 |866.70 MHz|
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| 16 |867 MHz|
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| 17 |868 MHz|
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## North America Frequency Bands
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Power limits will generally be lifted in the software if `is_licensed` is set to `true` [HAM Mode](/docs/faq#amateur-radio-ham))
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### 915 MHz (ISM Band)
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The maximum output power for North America is +30 dBm ERP ([Effective Radiated Power](https://en.wikipedia.org/wiki/Effective_radiated_power)).
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The band range is from 902 to 928 MHz.
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There are thirteen channels defined with a 2.16 MHz gap between them. Channel zero starts at 903.08 MHz.
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|Channel Number| Center Frequency|
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|:---:|:---:|
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| 00 |903.08 MHz|
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| 01 |905.24 MHz|
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| 02 |907.40 MHz|
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| 03 |909.56 MHz|
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| 04 |911.72 MHz|
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| 05 |913.88 MHz|
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| 06 |916.04 MHz|
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| 07 |918.20 MHz|
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| 08 |920.36 MHz|
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| 09 |922.52 MHz|
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| 10 |924.68 MHz|
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| 11 |926.84 MHz|
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| 12 |915 MHz|
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## Data Rates
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### Considerations
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Various data-rate options are available when configuring a channel and are inversely proportional to the theoretical range of the devices.
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- **Spreading Factor** - How much we "spread" our data over time.
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- Each step up in Spreading Factor doubles the airtime to transmit.
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- Each step up in Spreading Factor adds about 2.5db extra link budget.
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- **Bandwidth** - How big of a slice of the spectrum we use.
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- Each doubling of the bandwidth is almost 3db less link budget.
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- Bandwidths less than 31 may be unstable unless you have a high quality Crystal Oscillator.
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- **Coding Rate** - How much redundancy we encode to resist noise.
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- Increasing coding rate increases reliability while decreasing data-rate.
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- 4/5 - 1.25x overhead
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- 4/6 - 1.5x overhead
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- 4/7 - 1.75x overhead
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- 4/8 - 2x overhead
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### Predefined Channels
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We have six predefined channels. These are the most common settings and have been proven to work well:
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| Channel setting | Alt Channel Name | Data-Rate | SF / Symbols | Coding Rate | Bandwidth | Link Budget |
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| :------------------: | :---------------: | :------------------: | :-----------: | :----------: | :--------:| :---------- :|
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| Short Range / Fast | Short Fast | 6.8 kbps | 7 / 128 | 4/8 | 250 | 137dB |
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| Short Range / Slow | Short Slow | 3.9 kbps | 8 / 256 | 4/8 | 250 | 140dB |
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| Medium Range / Fast | Medium Fast | 2.2 kbps | 9 / 512 | 4/8 | 250 | 143dB |
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| Medium Range / Slow | Medium Slow | 1.2 kbps | 10 / 1024 | 4/8 | 250 | 146dB |
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| Long Range / Fast | Long Fast | 0.67 kbps (default) | 11 / 2048 | 4/8 | 250 | 148.5dB |
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| Long Range / Slow | Long Slow | 0.18 kbps | 12 / 4096 | 4/8 | 125 | 154dB |
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| Very Long Range - Slow | Very Long Slow | 0.05 kbps | 12 / 4096 | 4/8 | 31.25 | 160.1dB |
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:::note
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The link budget used by these calculations assumes a transmit power of 17dBm and an antenna with 0dB gain. Adjust your link budget assumptions based on your actual devices. Data-rate in this table is actual measured but doesn't count mesh overhead, hops and re-transmissions.
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:::
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### Custom Settings
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You may want to select other channels for your usage. The other settings can be set by using the Python API.
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```shell
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meshtastic --ch-set spread_factor 10 --ch-set coding_rate 4 --ch-set bandwidth 125 --ch-index 0
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```
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After applying the settings, you will need to restart the device. After your device is restarted, it will generate a new crypto key and you will need to share the newly generated QR Code or URL to all your other devices.
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Some example settings:
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| Data-rate | SF / Symbols | Coding Rate | Bandwidth | Link Budget | Note |
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| :---------:| :-----------:| :----------:| :--------:| :----------:| :----------------------------------------------------------------------- |
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| 37.50 kbps | 6 / 64 | 4/5 | 500 | 129dB | Fastest possible speed |
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| 3.125 kbps | 8 / 256 | 4/5 | 125 | 143dB | |
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| 1.953 kbps | 8 / 256 | 4/8 | 125 | 143dB | |
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| 1.343 kbps | 11 / 2048 | 4/8 | 500 | 145dB | |
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| 1.099 kbps | 9 / 512 | 4/8 | 125 | 146dB | |
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| 0.814 kbps | 10 / 1024 | 4/6 | 125 | 149dB | |
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| 0.610 kbps | 10 / 1024 | 4/8 | 125 | 149dB | |
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| 0.488 kbps | 11 / 2048 | 4/6 | 125 | 152dB | |
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| 0.336 kbps | 11 / 2048 | 4/8 | 125 | 152dB | |
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| 0.073 kbps | 12 / 4096 | 4/5 | 31 | 160dB | Twice the range and/or coverage of "Long Slow", low resilience to noise |
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| 0.046 kbps | 12 / 4096 | 4/8 | 31 | 160dB | Twice the range and/or coverage of "Long Slow", high resilience to noise |
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The link budget used by these calculations assumes a transmit power of 17dBm and an antenna with 0dB gain. Adjust your link budget assumptions based on your actual devices.
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These channel settings may have not been tested. Use at your own discretion. Share on <https://meshtastic.discourse.group> with your successes or failure.
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## Cryptography
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The pre-shared key (PSK) used by the devices can be modified.
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- 0 = No crypto
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- 1 = Default channel key
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- 2 - 10 = The default channel key, except with 1 through 9 added to the last byte
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Use of cryptography can also be modified. To disable cryptography (maybe useful if you have Ham radio license):
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```shell
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meshtastic --setchan psk 0
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```
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