Its so, he has a simple small bandwidth scope_I think in reality no chance to organize a higher bandwidth type, and 1 GHz so & so not.
I know otherwise, that good scopes (i.e. Tek & LeCroy, maybe HP too) have a linear roll-off of 6dB/octave, what means if you have to test a 900MHz signal & the trigger is in function usually so 2-40% over nominal bandwidth: relative sure is that you can apply a 500 MHz scope for a 900MHz signal, but I know=its a poormans solution, & possible will the scope not trigger.
In all case is the amplitude good predictable and to see...
For 1.8GHz clearly is only a detector to use_or some expensive scope...
Alternative can be in my opinion, a spectrum analyzer, but their are in 1.8GHz version not in all home labors too... :-(
Other important question is for me: where is the test signal from?
K.