Although NETC.com will not sell the GMC-200 ($85) units anymore, GQ Electronics still does:
http://www.gqelectronicsllc.com/comersus/store/comersus_viewItem.asp?idProduct=4527I own many of the GMC-200 units and they make a great unit for a low cost outside/inside radiation monitoring station. I still believe that if you want to build a low cost outside radiation station and plan on using it on a Holmes HAP242-UC HEPA air purifier like I have done, the GMC-200 is still the best I have found to use. I say that because the GMC-200 is small enough to fit on the face of the air purifier filter intake while leaving enough filter for hot particles to collect around it. This helps to increase the detection of the radiation which in turn makes the pattern/trends more visible in the graphs.
Using the ($85) GMC-200 geiger counter and the FREE Windows PC software from NETC, you easily have a radiation monitoring station for less than $100. Remember that as the station operator, you have access to
ONLY your stations chart data. The FREE software can be found here:
http://www.netc.com/software/If you want access to all the other stations chart data, you must subscribe to be a chart member which is currently priced at $19.95 per year. This yearly membership fee helps to cover the bandwidth cost and new feature developments. To help offset monthly bandwidth costs (much of that caused by free viewing of the public map and free hosting of radiation monitoring stations) NETC does have ads on the free public pages. If you see an ad that interests you, please feel free to click on it and know that you are helping to support the networks free features. There are NO ads when viewing the "Chart Member Rad Map"
As with anything else, there are +/- for everything and you need to decide which unit is best for what you want. For example, the GMC-300E and GMC-320 both have an internal memory which in the event of a loss of internet connection those two units will retain all the data and pass it to NETC when the internet connection is restored. When using the Raspberry Pi with the GMC-200, the Raspberry Pi will save the data in the event of a loss of internet and upload the missing data when the internet is restored. If power is lost, only the GMC-300E and GMC-320 will retain the data and this is the main reason that ADMIN "hey" / Harlan decided to no offer the GMC-200 units anymore.
I also own a GMC-300 that I carry around with me everyday as I monitor background radiation levels, an InspectorEXP and Mazur 9000 that I use for rain samples along with field testing. I also own a Polimaster 1703MO-1B that I can use for isotope identification.