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I have a pair of HopeRF LoRa RFM98 Radio Modems(based on Semtech SX1278) and I want to configure them for the longest range possible, without taking care about any second factor like transmission time and power consumption.

I made already some research until I found Semtech's official tool 'LoRa Modem Calculator Tool'. The problem is I am a beginner in the hobby of radios and the tool is just confusing for me with all the various settings.

Does the tool show me all relevant configurations to achieve the longest range with my RFM? How I have to choose the settings to achieve the longest range. Any other factor is not important.

Tools default settings: LoRa Medom Calculator Tool default settings

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  • $\begingroup$ What range are you getting now? $\endgroup$ – captcha Jun 20 '17 at 4:19
  • $\begingroup$ I once heard that the "Low Datarate" option should be on to achieve long range operation. $\endgroup$ – peter Jun 20 '17 at 7:04
  • $\begingroup$ This is neither about ham radio especially nor generally applicable radio theory, and hence off-topic here. Might be better suited for electronics.stackexchange.com ! $\endgroup$ – Marcus Müller Jun 20 '17 at 10:08
  • $\begingroup$ It is about radio theory and about 'Amateur Radio'! All the different settings like Spreading Factor, Coding Rate and RF Performanche, which the calculator tool calculates for your Amateur Radio settings. $\endgroup$ – William Roy Jun 20 '17 at 10:28
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    $\begingroup$ On topic or not, it's not a very good question. If "too localized" was still a close reason I'd use it here. Instead of asking us to tell you exactly what to do for a problem very specific to a device most of us probably don't even know exists, why not ask about the theoretical concepts that you don't understand, and then you can make the right decision yourself? $\endgroup$ – Phil Frost - W8II Jun 20 '17 at 15:57
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If your interest is simply to increase range, the metrics to watch on the tool are the "Link Budget" and the "Receiver Sensitivity" (lower right screen). These two numbers will change in concert. You want to look at any settings that increase the link budget. These will create a corresponding increase (more negative) in Receiver Sensitivity.

For example, if you change the bandwidth from 500 kHz to 250 kHz you will see a corresponding increase in link budget and receiver sensitivity.

Not all settings will affect the link budget but those that do, you should examine to see if they will fit your application requirements.

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