I bought this low cost DSO150 ("DSO Shell") pocket scope from AliExpress for under $20 incl shipping.

http://www.aliexpress.com/wholesale?catId=0&SearchTexct=dso-shell 

This video is about debugging techniques for when your QCX construction didn't quite result in a working QCX. The methods described and demonstrated with the cheap 'scope are also applicable to more advanced 'scopes. See also the QCX troubleshooting page

Also shown, are how to use a cheap DVM, and even the built-in DVM on the QCX, to carry out debugging of the Receiver section.

Finally I transmitted some CQs on 40m CW and after the third CQ, had a nice QSO with Nick LZ1NG.