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> Theorical Radio Range Given Sensitivity, Friis formula in free space
Posted: October 04, 2017 06:57 pm
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Hello all,
I have a transceiver with 20dBm of transmitting power and -121dBm sensitivity. I've calculated the theorical range, with a 2.15dB gain in transmission and reception, and it resulted to be 1000km! Did I make any error? I've verified the value with an online calculator, and the received power resulted to be -121dBm when the distance is 1000km.
Thank you.
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Posted: October 05, 2017 07:02 pm
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If the bandwidth is fairly small (should be rolled into the sensitivity already), that sounds reasonable.

Note that such a link will be extremely unreliable, since it's half noise by definition.

IIRC, Morse code contacts have been made across the globe on less! Such distances can only be done in the SW band, of course. (Well, or with moonbounce, or satellite repeaters. The Moon is quite a bit further away though, so you need more power for that.)

Practical links have more loss (multipath, horizon, etc.) and so tend to use more power for less distance (like FRS radios, which are pretty powerful). Speaking of ISM band communications: those bands tend to be rather congested and noisy to begin with, worsening sensitivity a lot. That's how Wifi can be pretty bad, even when it's fairly powerful.


Answering questions is a tricky subject to practice. Not due to the difficulty of formulating or locating answers, but due to the human inability of asking the right questions; a skill that, were one to possess, would put them in the "answering" category.
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