I have a GMC-320S, its ok, I had to cut away some of the plastic so it could read a uranium source I bought. The plastic housing would shield the tube from most of the radiation of the source. There are little slits that would let some in, I just widened them with a dremel.

I wouldn't recommend it again, but if you received one as a gift, with a bit of tweaking, you'll be measuring random stuff in your house.

I've seen Cody (of CodysLab fame/infamy) use a GMC-320 Plus,[0] which runs about $130.

You can get the GMC-300E a bit cheaper, but with no temperature compensation sensor[1] it won't be quite as accurate.

[0] https://old.reddit.com/r/codyslab/comments/hk3jru/more_fun_w...

[1] https://www.gqelectronicsllc.com/support/GMC_Selection_Guide...

I have a GQ 600-RPS and I love it. It detects alpha, beta and gamma. Detection range is only a few inches, so you have to know what to look for. We take it on family outings and search for uranium rocks.

I really like my https://www.bettergeiger.com/ (no affiliation with them, I just own one and am happy with it) It uses a solid-state scintillator instead of the older and less sensitive Geiger-Müller tube.

Thanks :D

GQ makes several dosimeters, I own the dual-tube GMC-500+.

The cheapest single tube dosimeters will max out and saturate at radiation levels far below those that are immediately harmful to human health. (This was the source of the famous "3.6 roentgen per hour, not great, not terrible" meme-- he was looking at a meter that was reading off-scale high at 0.001 R/s)

If you're buying a dosimeter with the threat in nuclear war in mind, check the specs for maximum readings.

> "3.6 roentgen per hour, not great, not terrible" meme

Quote from HBO's Chernobyl, the dramatisization of Anatoly Dyatlov: https://knowyourmeme.com/memes/anatoly-dyatlov

A more balanced view of him: https://www.rbth.com/history/330525-anatoly-dyatlov-chernoby...

Aside: all of us, even the most competent engineers, can deny what is happening or make bad calls during an emergency, especially where everything is unknown during the initial stages. It takes very good training to teach us to make better emergency decisions - e.g. firefighter's training, and some military. Beware of selection bias in repeated deadly situations.

You are right max range is important for some applications, and most cheap Geiger counters saturate very easily (that two tube device you mentioned being a notable exception). Even still it is not great to refer to them as dosimeters because measuring dose with a low cost Geiger counter is risky at best. That's because they are calibrated to Cs-137. Some so-called energy-compensated Geiger tubes exist and give more accurate dose information, but they are not used in consumer-grade devices (or at least none that I've seen, and I own a ton and constantly study the market). Also Geiger tubes can pick up a lot of beta, and in that case it will dramatically overestimate dose because beta should be blocked in order to get an accurate dose reading, and none of the usual suspects do that. Even if beta is blocked, dose is often strongly overestimated due to the lack of energy-compensation I mentioned. That's one of the reasons I developed the Better Geiger S-1, to have an accurate and fool-proof high range dosimeter at a consumer-friendly price point ($149).

At the high end, the standard workhorse for really serious hobbyists and rock hunters is the Ludlum Model 3 with a 44-9 pancake probe [1,2]. Throw in a scintillation probe [3] if you really want to find needles in haystacks. There are perennial bidding wars on ebay for these things surplus, but the manufacturer has a very hobbyist-friendly reputation. They've walked me through a few DIY repair jobs on ancient equipment they were under no obligation to support.

1. https://ludlums.com/products/all-products/product/model-3

2. https://ludlums.com/products/all-products/product/model-44-9

3. https://ludlums.com/products/all-products/product/model-44-1...