[Test-Equipment] PC usb scope ...etc

[Alan Melia]

Floyd the scope advertised is a digital scope ....it is NOT a spectrum 
analyser that can work with a tracking generator. It merely takes a digital 
sample of the waveform .....0 to 20MHz ......and does an FFT on it, then 
displays the result. There will be not start/stop options or resolution 
bandwidth adjustments.

To tune a duplexer you need a combo that will sweep the frequency of the 
unit. I dont know what diplexor you want to tune but 20MHz is a bit low. 
There are units that do do this, but I am aware of the misleading blurb 
which though technically correct suggest uses it cannot achieve.

In conclusion if you are looking for an RF instrument avoid this one

Alan
G3NYK