I am trying to refurbish an electronic personal locator beacon (for rescue callouts for stranded hikers/sailors/pilots).

To do so to spec most devices require a GPS signal test (activation). There is a BNC output to couple directly to a receiver for analysis that emergency is being squawked.

But to avoid a false emergency, the device must be shielded.

Is there a standard construction or recommended material for shielding 406.1MHz transmitter? Would a metal box with BNC feed through be sufficient?


1 Answer 1


You require a Faraday cage. I suspect a PLB is small enough to use a test chamber for, which might make it easier.

You can create a suitable enclosure using a wooden frame covered with close mesh chicken-wire. Ideally, the DUT and the test equipment would be within that enclosure.

The output of the transmitter should be connected directly to a dummy load, of high quality, to reduce radiated leakage signals. Most RF communications test sets are built that way anyway.

Is there not an option to put the device into a test mode that reduces the output power/works on a discrete frequency/sends a 'TEST ONLY' message?

To be frank, since 406MHz is now the de facto distress frequency, monitored 24/7 worldwide by satellite, servicing them really is the domain of properly equipped RF workshops

  • \$\begingroup\$ Thank you for the input. I agree that servicing the transmitter is one thing, but there is also basic self test that is prescribed when replacing the battery cells, which involves activation to be 100% sure per mfg instructions (in a shielded box) , certainly I would set up a shop before endeavoring to recertify old equipment but was curious if I can do abbasic refurbishment of my old beacons with what I have in my lab now. \$\endgroup\$
    – crasic
    Dec 16, 2019 at 0:37

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