Recievers

This is a hybrid SDR reciever, when connected to an HF rig can display a waterfall - the Spectrum DSP M4-Plus has a touch sensetive 5-inch XGA LCD.  The M4+ version with intergrated extension port allows access to support wide-band allmode transceiver, covering 1.6 to 54* MHz, including FT8, WISPR & SSTV, when fitted with HF head unit.

The M4+ User Guide
Latest user guide 

Official Facebook Page
Other than email the only method of support.

Official YouTube page
The official Youtube page with setup guides.

Andreas' Learning YouTube page
Including some speculation on the upcoming TX functions.

M7MCQ Blog
An excellent  review of the DSP2 SDR reciever.

Tech Minds Review
Brilliant balanced review, as ever.

Amateur Radio Blog
DSP2 pages.