767 with significant history of the left Weather Radar Transceiver failing.
Several parts had been replaced, but the problem persisted.
While doing a visual of system components.... we saw this
This is a section of waveguide, forward of the bulkhead that has a separation at the joint from solid to flexible.
The waveguide is basically a hollow tube (appox 1" x 3/8') that is used to transport microwave energy between the R/T and antenna. Aircraft with dual R/T's use a waveguide switch to route the transmit/receive energy to the selected system R/T.
What is interesting about this particular problem is that the signal loss through this opening should of been recognized by "both" R/T's. We found "one" problem, but did we fix "the" problem??? (Time will tell)
It can't be seen with the naked eye, but the antenna scan is not a smooth horizontal motion. It actually stops, sends/receives a signal, and then moves to the next position where it stops to completes another signal shot.
Some weather radar systems have a vertical trace also.
More advanced R/T's can predict windshear "before" the aircraft actually flies into one. EGPWS's tell you that you're "in" a windshear situation.
I found a Collins manual (really meant for pilots) that has quite of bit of information about weather radar systems.