{"id":757,"date":"2026-05-27T14:27:14","date_gmt":"2026-05-27T22:27:14","guid":{"rendered":"https:\/\/salemdata.net\/johnpress\/?p=757"},"modified":"2026-05-27T14:27:14","modified_gmt":"2026-05-27T22:27:14","slug":"bluetooth-signal-strength-testing","status":"publish","type":"post","link":"https:\/\/salemdata.net\/johnpress\/?p=757","title":{"rendered":"Bluetooth Signal Strength Testing"},"content":{"rendered":"

Now that I have Bluetooth working with Reticulum on the T-Beam, I have the option of testing my Reticulum mesh using Bluetooth instead of Lora. Were I using LoRa, I would have several people walking the neighborhood in an expanding circle fashion so that each node can only reach one other node. This requires having people at large distances from one another.<\/p>\n

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4 LoRa Units – Out Of Range<\/figcaption><\/figure>\n

Here is an illustration of four radio units: BOB, CY, DAN & ED.\u00a0 The green radial gradients represent their transmission reach.\u00a0 Each is far enough for any other that none of them can communicate with another; they are isolated.<\/p>\n

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Mesh Network<\/figcaption><\/figure>\n

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Here is the isolated network above enhanced by three more units interposed so as to create a continuous “mesh” network.
\nI have positioned 7 units named: AMY, BOB, CY, ED, FLO & GUY.\u00a0 Furthermore, I have created arrows indicating the only transmission<\/em> ability between two given units.\u00a0 BOB and AMY can communicate directly.\u00a0 For BOB to reach CY, packets must route through AMY, so BOB->AMY and AMY->CY.\u00a0 In mesh terminology, this is called a “hop”.\u00a0 For BOB to reach ED, packets have to traverse 3 hops: BOB->AMY, AMY-> FLO and FLO->ED.\u00a0 For BOB to reach DAN, packets must traverse 5 hops.\u00a0 I want to stress test Reticulum and doing so over LoRa requires placing units on the fringe of their transmission capability.\u00a0 Bluetooth transmission capability is much less than LoRa, so if I use Bluetooth, I can narrow of the universe of units in the field to a much smaller area.<\/p>\n

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Instead of using LoRa as the transmission method, I can simulate the isolation by using Bluetooth.\u00a0 Bluetooth transmissions are measured by Received Signal Strength Indicator (“RSSI”).\u00a0 A low RSSI, e.g. -20 is a stronger value than -60. So i wanted to get a feel for what distances might be needed to create a weak RSSI between two unit so I could create a mesh purposefully by placing two units so far apart, they cannot see their signals, but if I place a third unit in between, the middle unit can transport each end unit’s package to the other.\u00a0 Hence, I wanted to test signal signal strength by having two units remain stationary and then I would hand carry two more units away from the stationary units to a point where I believe they two sets are out of range and then return.<\/div>\n
Below is a graph of such an experiment where at the beginning, all four units are close together.\u00a0 Units BOB & CY remain stationary and constitute the “base” and I carry units ED & FLO away from the base about 120 feet and then return.\u00a0 As I move, all the units are sending Bluetooth announcements and likewise each unit is recording what has been received along with the RSSI.<\/div>\n
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The graph below shows time on the X-axis.\u00a0 At the commencement of the test the two carried units, ED & FLO, have strong signals between them and the stationary units.\u00a0 Then as I walk away, the signals weaken until there is no longer a received signal..\u00a0 As I retrace my steps and return to the base, the RSSI values become stronger, moving from roughly -90 dBm back toward -50 dBm.<\/div>\n
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