Sorry to bring up an old topic, and especially so for it being my first post. I am an amateur ore/geiger counter collector and civil defense enthusiast, and searched the internet for information regarding these filters when I happened upon this thread.
It seems Ludlum wanted to, for whatever reason, turn the 44-9 into an energy unit reading probe with these filters. I had always been under the impression that the 44-9 was meant for measurement in counts and for contamination searching/frisking, not taking dose rate or exposure measurements. It's a cool concept though, a highly sensitive search probe that can be turned into a roentgen/rad/rem measurement probe just by snapping in a filter shield. I see a lot of geiger counters on ebay that measure in roentgens, but come with alpha/beta/gamma pancake probes which never made sense to me, and it seems such a filter would alleviate this obvious issue with being able to use the mR scale on a counter with that sort of probe. Although I imagine the filter blocks out most if not all of the beta particles it'd otherwise detect, so how could one get a true dose rate in REMs while ignoring beta?
One other thing I don't get about the filters is that the exposure filter has a flatter response curve than the dose rate filter. If you're looking to get the counter to give you an accurate representation of what the biologically effective dose is, wouldn't you want the exposure filter because of this?
I've also read from multiple sources that in *most* cases, a Cs137 calibrated detector will give you an accurate exposure and absorbed dose rate without having to convert from roentgens even without an energy compensated tube. Basically, if you're reading 10mR on your counter, you're likely being exposed to 10 millirads/millirems. Is this true? If it is, do either of these filters help you come to the *biologically* effective dose rate (sieverts)? I'm aware that to get the biological effect from a set amount of REMs or RADs you need to apply the "quality factor" to each, but I'm not sure if there's a seamless way to get Sv from a R/Rem/Rad measurement from a filtered 44-9 or even a CDV-700 mR reading. I'm also not sure (if all this is indeed the case), if the CDV-700 would give a more accurate absorbed dose or biological effect rate measurement since it can account for beta whereas the 44-9 (at least I presume) cannot. However, my CDV-700 manual states to read the CPM scale with the beta shield open, and the mR scale with the beta shield closed. I've also seen this actually printed on the meter scale itself on a few commercial geiger counters. This further confuses me. Can these counters not get an accurate roentgen measurement with beta being taken into account? If not, then how does the supposed general rule of one mR equaling one mRem and mRad stand? Wouldn't this underestimate the biological impact of the radiation field, and thus the actual mR/mRad/mRem reading??? Sorry for the confusing post, my brain can barely comprehend all of this at the same time.
EDIT: The dose equivalent filter actually has a flatter response curve than the exposure filter, and REMs are also quality factor compensated already. Sorry. Please take this into account when replying.