I would guess the "M" variant is a revised model...somehow...now we need new photos to compare...
BTW: Also available from Warren Electronics:
http://www.warrenelectronics.com/Antennas/ant2000m.htm
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NAB Report is for A-D Prototype Smart Antenna...which only operated in UHF Band...so no help for VHF...
Also note big differences between VSWR performance in theory...and actual implementation
in Microstrip Disc alternative...and then they fell back to existing Lacrosse/Micron design
with little or no performance data in the delivered report.....thanks a heap....
What they developed and tested for NAB presumably was a "proof of concept" for
outputting control signals directly on the coax, rather than going through an external
"Power Insertion Module" (hardly a high tech effort--relocate the PIM inside the tuner).
And the one and only "Made In USA" Smart Antenna for DTV.....hmmmm.....
Too bad they interpreted NAB "specs" to mean VHF coverage was not a requirement.....