After my QDX's finals bit the dust due to the remote ATU doing a re-tune cycle during transmit, I added some simple VSWR protection devices like shown. These devices are just something I had in my junk parts bins.
I can now transmit without an antenna connected and not destroy the finals. Output spectra was not affected and meets current FCC limits for spurious emissions.
A voltage-clamping diode has been on every <= 5W solid-state QRP rig since .. the 70s? Cheap insurance.
--- Zach
N0ZGO
