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Why a bench test shows no DJI detections

Updated October 15, 2026

The most common reason is not the unit. DJI aircraft broadcast DroneID only while the motors are spinning.

Run the test this way

1. Start the aircraft’s motors. Powering it on is not enough; a DJI aircraft sitting on the bench with its lights on will not appear, however close it is to the unit.
2. Open the WarDragon Console and go to the Drones tab.
3. The aircraft should appear within a few seconds of the motors starting.

Remote ID broadcasts from other aircraft behave differently and may appear while the aircraft is stationary, which is why a bench test can show Wi-Fi or Bluetooth detections and no DJI detections at the same time.

If the motors are spinning and there is still nothing

Work through these in order. The first two can be checked on the Console; the rest need a terminal on the unit.

1. Confirm the antenna etched DRAGON SDR is screwed snugly onto the port labeled Dragon SDR. This is the primary DJI receive port. A loose or swapped antenna is the most common hardware cause. See Antennas.
2. Check the DJI receiver on the Console’s Receivers tab. If it shows down, continue below.
3. Confirm all three detection services are running:

sudo systemctl status zmq-decoder dji-receiver dragonsync

4. Watch the DJI receiver log while the aircraft’s motors are running:

journalctl -u dji-receiver -f

5. Confirm the detection stream itself is producing data. This listens for ten seconds and prints the first message it receives:

timeout 10 python3 -c "
import zmq
c = zmq.Context()
s = c.socket(zmq.SUB)
s.connect('tcp://127.0.0.1:4221')
s.setsockopt_string(zmq.SUBSCRIBE, '')
s.setsockopt(zmq.RCVTIMEO, 5000)
try:
    print('DJI DroneID:', s.recv_string()[:100])
except:
    print('DJI DroneID: No data')
"

If the services are active and the stream still reports no data with motors running in range, restart the detection services and try again:

sudo systemctl restart zmq-decoder dji-receiver

Critical If at any point you have changed Wired connection 1 or the addresses 172.31.100.1 and 172.31.100.2, that is the cause. That connection is the internal link to the detection SDR and must stay as shipped.

Still nothing

Open a support request and include the output of the service status command and a diagnostic bundle. See Opening a support request and building a diagnostic bundle.

Related

• WarDragon User Guide, Section 6 — verifying detection services
• WarDragon User Guide, Section 10.4 — no detections

WarDragon is manufactured by Millenium Products Inc. Technical support for purchased kits is requested through the support page. Purchasing and quote requests go through the contact form.