CAUTION! Do not power on without main antenna connected!

[jaclaz]

It is a standard disclaimer, the Ax3 has similar label.

Theory wants that you power a radio only with a load connected to it, be it an actual antenna or a dummy one like (example):

https://hamparts.shop/sma-dummy-load.html?

On low power devices, such as the knot, it is improbable that anything will burn, but you never know.

Please note that IF something will burn, it will be something difficult to troubleshoot and replace, see:

is it me, or is it the wAP ax?

What the sticker sayeth is the truth. The device is designed to be terminated into a load of 50 ohms (50R) at the antenna connectors. If the emitted RF power of the transmitter is not absorbed external to the device, the power is reflected back, which causes excess dissipation (EE speak for fries) the TX amplifier. The resulting standing wave patterns may also load the LNA (low noise amplifier, on the RX side) beyond its design limits (again, fry) Antennas of course are coupled to the free spac…