The web site is: http://www.frequencymanager.de/TH/th.html
There are print books for sale for HF modes and another for VHF/UHF. Roland Proesch is the author. (The books are available in german and english)
For each book a PDF except is available for free that still has lots of helpful information in it.
In addition to a brief description for each signal are a number of pictures of oscilloscope and sonogram/waterfall type views.
RTL-SDR users would find the VHF/UHF book directly relevant. However the HF book looks like it might provide a better foundation.
Take a look at
- HF: (81 pages) - http://www.frequencymanager.de/TH/files/KurzfassungTechnicalHandbookHF2013E.pdf
- VHF/UHF: (56 pages) - http://www.frequencymanager.de/TH/files/KurzfassungTechnicalHandbookVHF2013.pdf
I've also forwarded this to rtl-sdr.com which I find is a very useful blog for SDR and digital modes.