| T O P I C R E V I E W |
| Deputy |
Posted - 08/23/2013 : 11:36:28
I would like to know EXACTLY what the range is of this unit. I know ZLM has stated you can mount this unit on a wall "so that you can monitor each day's radiation level changes in particular area."
What EXACTLY are you monitoring? I can walk into a room containing multiple radioactive ore sources of different types (all but one are pretty "warm"), be 3 feet away from them but in direct line of sight, and the GMC-300E does NOT change it's CPM AT ALL. As a matter of fact, the CPM DROPS!!!!
This makes me wonder just what the unit is detecting when I walk around the house and it is clicking and the numbers are increasing and decreasing. It also makes me think this unit is pretty worthless at detecting radioactive objects unless they are placed right next to it. So if anyone has any plans to use this to detect radioactive ore in thw wild, get ready for lots of stooping over or crawling around on your hands and knees. Good grief, my CDV-700 is more usefull at searching out radioactive ore and it's birthday is 1954. |
| 7 L A T E S T R E P L I E S (Newest First) |
| XRumerTest |
Posted - 01/12/2015 : 17:40:23
Hello. And Bye. |
| Deputy |
Posted - 08/27/2013 : 19:09:47
Harlan: I am discussing alternatives to the GMC300 on the NETC.com forum:
www.netc.com/bb/viewtopic.php?f=10&t=341
So far the only one that interests me is one made by an individual on YouTube:
www.youtube.com/watch?v=S9M5MNe-9hA
Not sure what the price is, but it has all the features I want.
I have also been considering the GMC200. Since it is so inexpensive, I can afford to risk another GMC product. But I can't put it outside. We are in the "monsoon season" in my area and I don't trust the case to protect it against excessive moisture, whether through himudity in the air or condensation in a ziplock. |
| harlan |
Posted - 08/26/2013 : 13:30:27
I installed another GMC-300 and the Raspberry PI in HotSprings last week. She set it on a table, and covered it with a plastic box so that it would not get wet. The next day, she removed the plastic box and within a few minutes the GMC-300 was sounding off with the alarm. The only thing I could think of is the dew was radioactive and some of it dropped near the unit. Bottom line - get the units outside !!! |
| Deputy |
Posted - 08/25/2013 : 13:43:07
So it would seem that this geiger is more useful for detecting a nuclear attack or dirty bomb than any type of ore-prospecting. I already have a K8 for that, though. Either that, or just for measuring ore that you already have. I still don't get hanging it on a wall, though. And if you are close to a nuke going off, the EMP will probably destroy the 300E anyway. |
| Dan |
Posted - 08/25/2013 : 13:29:22
It is because the radiation emitted from the ore is really pretty low, so when you get any distance from it, it drops fast, it would do this with any kind of Geiger counter, with the most sensitive Geiger tubes getting a higher reading further away.(Google "inverse square law")
For instance a "pancake" style Geiger tube would be a lot more sensitive than any round tube style for that matter, the m4011 tube that we have installed is pretty good as far as "tube" style Geiger tubes go anyway...
But the "pancake" Geiger tube costs about 200-250$ for just the tube which is way more than we paid for the gmc-300, for the money the gmc-300 is a lot better than anything else in it's price range.
I suspect the cdv-700 is better at picking up the beta particles with it's open window.
But I know from detecting my ore I get almost 3 times higher cpm (similar mR/h) as a cdv-700 (with shield closed) does up close, about 3" away. |
| Deputy |
Posted - 08/25/2013 : 07:01:34
Thanks Dan. That may be the problem. I don't see myself drilling holes in it. That might affect warranty issues.
As to using it to search for radioactive ore...forgetaboutit. A better way to search out radioactive ore is to buy a UV flashlight and go hunting for it at night. Easier and more effective than crawling around on the ground touching each rock.
More and more I am seeing less and less uses for this unit. It's main use seems to be measuring chunks of radioactive materials that are placed close to it. I am beginning to think I made a mistake and should have bought the GMC200. It has a light to indicate radiation as well as an audible indicator.
As a "constant monitor" I'm not sure how effective it really is. |
| Dan |
Posted - 08/23/2013 : 21:36:16
I suspect it's because of the plastic case on the gmc-300 most likely cutting down on the beta, while the cdv has a "window" you can open...
if you look at the front of the gmc-300 you can see a thin layer of plastic right below the buttons, it is right over the tube, on my Geiger counter that is the most sensitive spot... Almost like a window.
I seen a post on here awhile back where someone drilled nice clean holes on the bottom to let in beta reach the tube directly. |
