My comparison of AIS messages received over a 30 minute period, showing 40% more messages received on ShipTrax compared to my Comar receiver. Obviously not the most scientific of tests, but a reasonable comparison over a one hour period.
COMAR AIS2USB
(http://farm6.static.flickr.com/5249/5226787899_5ede762e78_m_d.jpg) (http://www.flickr.com/photos/tarbat/5226787899/sizes/o/in/photostream/)
http://www.flickr.com/photos/tarbat/5226787899/sizes/o/in/photostream/
SHIPTRAX Beta Hardware
(http://farm6.static.flickr.com/5250/5227382818_157c368e2e_m_d.jpg) (http://www.flickr.com/photos/tarbat/5227382818/sizes/o/in/photostream/)
http://www.flickr.com/photos/tarbat/5227382818/sizes/o/in/photostream/
(http://farm6.static.flickr.com/5017/5515422018_78a9b6de53_m_d.jpg) (http://www.flickr.com/photos/tarbat/5515422018/sizes/o/in/photostream/)