More TX Power Can Make the Experiment Worse

One of the fastest ways to get lost in LoRa debugging is to treat silence as one failure mode. Here, A high-power remote module made it tempting to run both nodes at maximum output during bench debugging.

This series comes from a small hands-on LoRa/Reticulum lab rather than a commercial coverage benchmark. The working set included Reticulum on Linux, RNode-class devices, a Waveshare ESP32-S3/LR1121 board, an ESP32-C6 bridge, an SX1262-class RNode, and EBYTE E22/EWM modules. Different devices used different bands and profiles; I keep those experiments separate instead of merging them into one imaginary “LoRa setup.”

The evidence for this case was specific: The E22/EWM package deliberately used low temporary power and recommended several metres of separation while noting that the remote device could reply at much higher power. I use it as evidence from that test topology, not as a universal radio claim.

The retained result was: Initial tests favored controlled low-power conditions and explicit spacing.

How I framed the problem

I approached this as an experiment-design problem. Starting from A high-power remote module made it tempting to run both nodes at maximum output during bench debugging., I chose an observation that could separate at least two plausible causes: The E22/EWM package deliberately used low temporary power and recommended several metres of separation while noting that the remote device could reply at much higher power. The result made sense because Near-field coupling, receiver compression, poor antennas and regulatory/thermal constraints can make excessive bench power a bad diagnostic default. It also prevented me from treating Turning power to maximum before proving mode, profile and antenna state. as proof. The retained result was Initial tests favored controlled low-power conditions and explicit spacing.

Range discussions become useful only after the antenna and link budget are real. TX power is one term. Antenna match, cable/connector loss, receiver sensitivity, PHY, interference, terrain, height and margin all matter. A test with the wrong antenna or an unknown remote mode is not evidence for maximum distance.

The rule I carried forward was: Use the minimum power that makes the intended diagnostic observable. That rule is more useful than remembering one working frequency or one USB device name because it changes how the next experiment is designed.

Evidence matrix

I keep this table because radio work is unusually vulnerable to folklore. A missing packet can become “bad antenna,” “wrong SF,” “dead module” or “too close” depending on which theory is most convenient. Writing the evidence beside the theory forces the conclusion to remain narrower than the timeout.

The boundary I wanted to prove

Linux host / Docker
   |
   +--> Reticulum rnsd
   |      |-- RNodeInterface -> /dev/rnode -> USB/UART -> radio MCU
   |      `-- TCPServerInterface -> LAN peers
   |
radio firmware
   -> frequency + BW + SF + CR + sync word + power
   -> RF front end
   -> matched antenna
   -> propagation path
   -> remote radio profile/mode
   -> remote host / Reticulum

For this layer I wanted these checks before changing another parameter:

• use a band-appropriate antenna at both ends
• record TX power without making it the only variable
• document distance/height/environment
• know the receiver sensitivity/PHY assumptions
• keep margin for real deployment variation

The experiment-specific mechanism was: Near-field coupling, receiver compression, poor antennas and regulatory/thermal constraints can make excessive bench power a bad diagnostic default. That sentence tells me where the next measurement belongs. If the disputed state is host serial ownership, changing LoRa SF is irrelevant. If the disputed state is remote Mode 0, increasing TX power is not the first diagnostic. If a preamble IRQ fires without a header, the receiver is telling me more than a binary “no packet” counter would.

Investigation sequence

I keep physical prerequisites outside the software hypothesis. Correct antennas, stable supply and deliberate spacing are test conditions, not optional accessories. If they are unknown, the right conclusion is “RF evidence invalid or incomplete,” not a guessed range number.

The shortcut I avoided was Turning power to maximum before proving mode, profile and antenna state. That shortcut would have changed a convenient variable without increasing observability. In radio debugging, a new parameter is not automatically a new experiment; it is only useful if the expected evidence is written down first.

From bench experiment to infrastructure

The durable rule is Use the minimum power that makes the intended diagnostic observable.

If I keep this node running, I want the radio profile and host mapping versioned, the serial device stable, the container health tied to the Reticulum interface, and raw diagnostic evidence retained for failures. I do not want the only record of a working SF/BW/sync combination to be scrollback from one terminal.

I also want the physical layer documented with the same discipline. Antenna band, connector, placement and any gain/loss assumptions belong beside the radio configuration. Otherwise a later hardware substitution can change the link while the software repository remains unchanged.

At the Reticulum layer, I separate roles: which node is an endpoint, which is transport-capable, which interface reaches the LAN, and which interface reaches radio peers. That makes later scaling easier to reason about because every additional path has an owner and a failure model.

Instrumentation I would keep

TX power + TX antenna - losses - path loss + RX antenna
                         |
                         v
               received level vs sensitivity
                         |
                      margin

The instrumentation should make state transitions explicit rather than print only final success. For serial/host work I want device identity, open failures and interface initialization. For LoRa PHY work I want the full profile plus preamble/header/header-error/CRC/RX counters. For E22/EWM I want UART writes, AUX timing and remote reply counts separated. For Reticulum I want interface state and rnstatus-visible behavior.

The reason is simple: The E22/EWM package deliberately used low temporary power and recommended several metres of separation while noting that the remote device could reply at much higher power. was useful because it exposed an intermediate state. If I had recorded only “packet received = 0,” several very different failure modes would have looked identical.

I also preserve units and topology. Frequency is recorded in Hz or MHz explicitly, TX power in dBm, bandwidth in Hz/kHz, and distance only when the antenna/environment are controlled enough for the number to mean something. A number without its observation boundary is usually weaker evidence than it looks.

Acceptance test

For E22/EWM, I keep local-control PASS separate from remote-reply PASS. The canonical command must produce its expected remote response before I call the OTA configuration path compatible. AUX activity alone cannot satisfy that gate.

For this case the pass condition follows directly from the retained result: Initial tests favored controlled low-power conditions and explicit spacing. The test should observe that state, not infer it from a neighboring LED, process or log line.

Local success and end-to-end success are different

A recurring pattern in this lab was that one half of the system could be proven healthy while the complete link remained unknown. The Linux host could see the USB device. The container could run. RNS could parse its config. The local E22 could accept register commands. The LR1121 could arm RX. None of those facts alone proved that a remote radio decoded a packet and delivered it to Reticulum.

For More TX Power Can Make the Experiment Worse, the distinction matters because Near-field coupling, receiver compression, poor antennas and regulatory/thermal constraints can make excessive bench power a bad diagnostic default. The evidence The E22/EWM package deliberately used low temporary power and recommended several metres of separation while noting that the remote device could reply at much higher power. therefore supports a bounded statement, not a complete wireless PASS.

I now label test outcomes by layer: HOST, SERIAL, LOCAL_MODEM, PHY_DETECT, PACKET_RX, REMOTE_REPLY, RNS_INTERFACE and RETICULUM_PATH. That vocabulary keeps a green result at one layer from hiding an unknown state at the next.

The next experiment I would run

I would also reverse the test direction where possible. A result that survives transmitter/receiver role reversal is stronger than one that depends on an unexplained asymmetry in the lab setup.

The purpose is not to collect more logs. It is to remove one ambiguity. If the new test cannot distinguish two competing explanations, it is not yet the right next test.

The rule I kept

Use the minimum power that makes the intended diagnostic observable.

The retained result was: Initial tests favored controlled low-power conditions and explicit spacing.

The main thing I learned from this radio work is that “no packet” is not a diagnosis. The host, bridge, target MCU, local modem, PHY, antenna, path, remote mode and overlay protocol can all fail independently. The productive debugging loop is to expose one boundary at a time and make each experiment answer a question that the previous one could not.

That is also what made Reticulum useful as an engineering exercise. It forced the radio to become part of a network system rather than an isolated demo. Once the interface has a role, a health state, a recovery path and reproducible configuration, the lab starts becoming infrastructure.