Look into building a line sampler for use in examining your transmitted RF waveform.

Does your HF rig have an IF Out whose frequency is lower than the scope's maximum vertical bandwidth? Connect it to the radio via good quality shielded coaxial cable and look at off-air signals.

Do you still have the PK-232s I sent up? They have a tuning indicator output, accessible via the 5-pin DIN connector IIRC. Put the scope's timebase control (sweep) in Ext Horizontal mode, connect the Mark line to the Vertical input and the Space to the Horizontal, adjust the vertical sensitivity so the two signals are roughly the same amplitude then tune for "crossed ellipses".

There are many more uses...I'll let the others chime in here too.