915 MHz LoRa Antenna Comparison for Meshtastic (Measured with VNA)

Real-World 915 MHz LoRa Antenna Comparison for Meshtastic Nodes

Site: NWIMesh.net
Author: Matt – W9MDM
Test Equipment: Siglent Vector Network Analyzer (VNA)
Sweep Range: ~792 MHz – 1.02 GHz
Center / Marker Reference: ~906.875 MHz (used for “apples-to-apples” comparison)
Measurement: S11 (SWR + S11/Smith)

TL;DR

At the ~906.875MHz reference point used for this comparison, the Seeed SenseCAP stock antenna shows the lowest SWR and best single-frequency match. However, the ALFA AOA-915-5ACM is the better real-world performer for most Meshtastic installations due to its more consistent impedance behavior across the US-915 band, higher effective efficiency, and superior build quality.

The Clarifi 8dBi antenna is electrically clean and PA-safe but is a specialized tool intended for long, flat, horizon-level paths where its compressed vertical beamwidth is an advantage. The knock-off antenna can appear acceptable on SWR at certain points but relies on reactive behavior and internal loss, making it suitable only for low-power edge nodes. The LilyGo/T-Beam stock antenna performs poorly near 906MHz and should be replaced for any serious deployment.

Antennas Tested

ALFA Network AOA-915-5ACM – ~5 dBi Omni
Clarifi 915 MHz – ~8 dBi High-Gain Omni
Seeed SenseCAP Solar Pro P1 stock antenna – “868–915” included antenna
LilyGo / T-Beam stock 915 antenna – included antenna
Slinkdsco / Knock-Off 915 MHz Omni – third-party “Meshtastic” antenna

Important note: SWR and Smith charts indicate how the antenna loads the radio (impedance / mismatch). They do not directly measure gain or radiation pattern. High-gain antennas can still show “okay” SWR while being the wrong tool for a specific deployment geometry.

Quick Scorecard at ~906.875 MHz

This table is taken directly from the marker readouts shown in the screenshots below.

Antenna	SWR @ 906.875 MHz	Return Loss (S11) @ 906.875 MHz	Notes
Seeed SenseCAP P1 stock (868–915)	~1.14	~-21.84 dB	Best match at the 906.875 MHz reference point
Knock-Off Omni	~1.23	~-18.60 dB	Looks good electrically here; keep it on low-power / edge roles
ALFA AOA-915-5ACM	~1.34	~-15.98 dB	Good, stable behavior; strong general-purpose choice
Clarifi 8 dBi	~1.65	~-12.66 dB	Usable but not centered here; pattern matters more than SWR at 8 dBi
LilyGo / T-Beam stock	~3.61	~-4.84 dB	Poor match at 906; replace for anything beyond portable testing

SWR Screenshots (Tr1 S11 SWR)

These are the SWR sweeps. The marker value at ~906.875 MHz is the number used in the scorecard above.

Seeed SenseCAP Solar Pro P1 Stock Antenna (868–915) – SWR

Seeed SenseCAP P1 Stock Antenna SWR — SeedSolarNodeSWR.png — SWR at marker ~906.875 MHz is ~1.14.

Knock-Off Omni – SWR

Knock-Off 915 SWR — Knockoff915SWR.png — SWR at marker ~906.875 MHz is ~1.23.

ALFA AOA-915-5ACM – SWR

ALFA 915 SWR — Alfa915SWR.png — SWR at marker ~906.875 MHz is ~1.34.

Clarifi 8 dBi – SWR

Clarifi 915 SWR — Clarifi915SWR.png — SWR at marker ~906.875 MHz is ~1.65.

LilyGo / T-Beam Stock 915 Antenna – SWR

LilyGo 915 SWR — lilgo915SWR.png — SWR at marker ~906.875 MHz is ~3.61 (poor).

S11 “Smith Chart” Screenshots (Tr1 S11 Smith/Log)

These plots show the complex impedance behavior across the sweep. The value shown at top right is the marker return loss (dB) and angle at ~906.875 MHz. This helps explain why two antennas with “similar SWR” can behave very differently with real radios and PAs.

Seeed SenseCAP Solar Pro P1 Stock Antenna (868–915) – S11 / Smith

Seeed SenseCAP P1 Smith Chart — SeedSolarNodeSmithChart.png — Return loss at marker ~906.875 MHz is ~-21.84 dB (excellent).

Knock-Off Omni – S11 / Smith

Knock-Off Smith Chart — Knockoff915SmithChart.png — Return loss at marker ~906.875 MHz is ~-18.60 dB.

ALFA AOA-915-5ACM – S11 / Smith

ALFA Smith Chart — Alfa915SmithChart.png — Return loss at marker ~906.875 MHz is ~-15.98 dB.

Clarifi 8 dBi – S11 / Smith

Clarifi Smith Chart — Clarifi915SmithChart.png — Return loss at marker ~906.875 MHz is ~-12.66 dB.

What This Means in Practice (Important)

The Clarifi 8 dBi is not an “upgrade everywhere” antenna.

Compresses vertical beamwidth
Pushes RF energy toward the horizon
Can reduce performance for nearby or lower-elevation nodes

Because of this, placement and terrain matter more than SWR when deploying high-gain omnis.

LilyGo / T-Beam Stock 915 Antenna – S11 / Smith

LilyGo Smith Chart — lilgo915SmithChart.png — Return loss at marker ~906.875 MHz is ~-4.84 dB (very poor).

Which Antenna Should You Use?

Different node roles justify different antenna choices. For NWIMesh, the decision is mostly about node importance, terrain geometry, and TX power.

Best “Default” Infrastructure Choice

ALFA 5 dBi → general infrastructure, mixed terrain, predictable behavior.

Best Choice for SenseCAP P1 / P1 Pro Nodes

Seeed SenseCAP stock 868–915 antenna → excellent match near ~906 MHz, ideal for low-power solar nodes.

When to Use High Gain

Clarifi 8 dBi → long horizontal paths, flat terrain, tower-to-tower peers at similar elevation.

Budget / Edge Nodes

Knock-off omni → low-power edge nodes only (≤22 dBm), non-critical paths.

NWIMesh Rule of Thumb

Seeed stock (868–915) → SenseCAP P1/P1 Pro solar nodes (low power), best match at ~906 MHz
ALFA 5 dBi → general infrastructure, mixed terrain, nodes that matter
Clarifi 8 dBi → long-haul, flat-terrain backbone links where geometry supports a narrow vertical beam
Knock-off → low-power edge nodes only

Key Takeaway

SWR alone can be misleading. Use SWR and S11/Smith behavior to decide whether an antenna is a clean, efficient load for your node — then match the antenna’s gain/pattern to the node’s role in the mesh.