Using a ubitx as a receiver is harder as you have no metering. Hard to compare values!
Also using a radio with spurs to test one for spurs makes for added difficulty.
One possible is an all band radio doesn't have to be great or especially
selective or sensitive. In my earlier days a Hallicrafters S38 was a real
handy item, not much of a radio but it could detect RF.
Solution is to use a DVB-t stick that covers HF, or used a computer with sound card
and tap in to the product detector output and run spectran or similar (fldigi) to get
a quantifiable measurement. The other thing needed is attenuators both those
that can stand 10-15W (home brew works at HF) and step attenuators once
the power is below a few milliwatts.
If that sounds too complex then learning or club activity around how to do this
is in order.
I can make suggestions but all answers, all the time. Sorry, I'm doing the
learning part too as its one of the challenges I enjoy. I didn't always have all
the gear, I still learned the theory and made the measurements.