Signal Server changelog 

v2.23 - 14 August 2014
Improved diffraction model to work only for dips deeper than 20m and not to exaggerate result by an arbitrary figure (3)
Fixed false 'frequency too low' error message for FSPL model which was intended for Hata models only.

v2.22 - 
Fixed LOS not outputting bounds

v2.2 - 
Made .dot output opt in to save some disk space
Changed version number to line 1 of main.cpp instead of buried in code in two places.

v2.1 - 
Added experimental dual core support with -haf
Requires double the RAM

v1.3.8 - 16 Jan 2014
Added Free Space Path Loss model (with optional diffraction)

v1.3.7 - 30 Dec 2013
Added propagation model option (-pm)
Added HATA urban/suburban/open models (150-1500MHz) 
Added COST231-Hata (urban) model (1500-2000MHz) 
Added custom Knife Edge Diffraction option (-ked) to enhance new models
Removed unused variables 

v1.3.6 - 12 Aug 2013
Added LOS model for up to 100GHz 
Added 1 arc second (3600 pixels/degree) support (-res 3600)

v1.3.5 - 07 Jul 2013
Reduced maxpages to 9
Added memset() to clear DEM before use

v1.3.4 - 16 May 2013
High resolution SRTM1 1-arc second DEM support added.
Use -res 3600 and ensure .sdf files are produced with srtm2sdf-hd

v1.3.3 - 04 Nov 2012
Air planning:
Increased maximum Tx height to 60,000 (m/f)
Increased maximum Rx height to 60,000 (m/f)

v1.3.2 - 04 Oct 2012
Re-instated grey scale option to allow for terrain background.
Off by default. Enable with switch -t

v1.3 - 03 Jan 2012
Added user defined clutter layers from SPLAT! (-udt switch)

v1.2 - 31 Dec 2011
Max colours increased from 32 to 128
Radius value fixed at metric
Metric / Imperial conversion bug fixed

v1.1 - 08 Dec 2011
Max Tx altitude increased to 20,000(m) for high altitude aircraft. "Can you 'ere me now?"
Added 2 new options -tercon, -terdic for *custom* dielectric values and ground conductivity. -te terrain option remains. Use with care!
New Earth Dielectric range (Permittivity): 80 to 0.1
New Conductivity range (Siemens/m): 0.01 to 0.000001

v1.0 - 19 November 2011
SS released.