slightly OT WHERE and WHAT to buy for a good radiation meter?

Do you want a Geiger counter, scintillation counter, Geiger front end for a smartphone, or something for one of the Fukushima radiation monitoring network? Are you looking for alpha, beta, gamma rays, or combinations of these in a multi-channel analyzer?

Radiation maps:

I have a few commercial and home made Geiger and scintillation devices. I have several Victoreen/Lionel CDV-700 counters. You'll find deals like this: The only useful item is the left hand CDV-700. The other two are ionization meters which require huge amounts of radiation and are totally useless. The pens are quartz wire dosimeters, also of limited value.

There are real manufacturers of radiation monitoring equipment, but you won't like the prices. A new commercial Geiger-Muller counter with no data logging or analysis features starts at about $500. You're probably better off building your own. If so, you might want to gets some ideas from:

Also, there's a Yahoo group with some useful info:

Scintillation counters are the most interesting. It can be as crude as a block of PEN (polyethylene naphthalate) plastic, with a photo transistor shoved into a hole, to a photomultiplier tube in contact with a scintillating crystal: I've gotten tolerable results with an LED or phototransistor smeared with zinc sulfide phosphorescent paint (which only detects alpha particles, but that's what I wanted).

However, if you just want to play, any CMOS camera can be converted into a radiation detector: Just cover the camera lens with black electrical tape, download the app, and it should sorta detect something. I found it only works with gamma and is not particularly sensitive. There are also plug in and BlueGoof wireless radiation detectors, that talk to various smartphones.

Do some background reading, and come back with something more specific.

Incidentally, building a radiation meter is easy compared to finding accurate radiation sources.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

RAD meters were the rage when everyone was hyper over the a-bomb. Dosimeters, and RAD meters are available via surplus markets,and you have snubbed the two major sources. Hell, even GM tubes are rare as the helium used is a government controlled substance. Even the big boys in the oil patch have problems in that area.

I have a Ludlum model 3 with a 44-6 tube. Does the job for me. I got it on ebay sans cable for about $100. Ludlum sold me the cable for about $20 and included a manual. The cable used C connectors. Not BNC, but C. I figure it was worth $20 rather than trying to make one. I was at a DOE facility a few years ago and compared it to their calibrated meter on a test source. Accurate enough for me.

The deal is you will need way better sensitivity than the old civil defense meters you find at swap meets. The model 3 can sense background radiation, typically 5 to 15 uR/hr. That won't show up on an old civil defense meter, though you should probably hear the clicks.

The sensors are used in two manners. That is it has a gamma shield you can open or close. Just look it up on the Ludlum webiste:

I notice there are a lot of model 3 on ebay without tubes. The meters themselves are pretty simple. I suspect the tubes are what fails, which is why they are sold without tubes. It might pay to see what Ludlum charges for a new 44-6 or whatever you want. I doubt the meters themselves are defective.

I have never found any place hotter than 100uR/hr. That was out in the Mojave around Kelbaker, where they have a few uranium mines.

You are free to pay the full retail price if you don't want to use Ebay.

The nice thing about Ludlum unlike more of the civil defense manufactured gear, Ludlum is still in business and they support the old products.

If you are looking for hot rocks, you probably want to get a UV flashlight.

Have you tried it up in a commercial airplane at 37,000' inside the spallating aluminum tube you ride in? I did, some years ago. Quite a difference from ground level.

Jon

I don't imagine that there is much of a market in the space between hobby kits and industrial instruments with NIST-traceable calibration. Maybe the "dig a bunker in the backyard" survivalist sites have some?

One of my fun with a geiger counter stories:

-- Jeff Liebermann snipped-for-privacy@cruzio.com

150 Felker St #D Santa Cruz CA 95060 Skype: JeffLiebermann AE6KS 831-336-2558

Get the one called the 'Inspector' comes in different variations. They can be calibrated and traceable. If you looking for measuring specific kinds of radiation get one with the changeable filters.

Cheers

Only very bad radios ;-)

-- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

Thinking of 455kHz.

Jon

Crap. I'll probably get shot without warning for wearing my tritium dial watch, then. ;)

Jon

I think you meant local oscillators. Any oscillation at IF is called instability.

--
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled." 
                                       (Richard Feynman)

Yes. That's what I meant. It was me conflating "IF frequency" with "local oscillator" into a mush. Cross-purposes between us at an end now. Lesson learned.

I was merely pointing out that a receiver's local oscillator can act like a weak CW xtr, because that was a reason given to me to stop me from using any personal receiver at some point in my frequent flying career.

This all goes back quite some years when this was an issue for me.

I used to listen to tower traffic when it was offered by the flight services I used. I learn better technique for when I pilot a small plane in controlled airspace. (And yes, I got some nice laughs from time to time.) Then I had that option removed by those same services. So I began bringing my own receivers on board. Then perhaps a year or two later they told me I couldn't use those receivers inside the plane -- even when sitting at the gate and not moving. I had a nice discussion with appropriate "officials" and got pretty much the same boilerplate -- the radios may "interfere" with their communication. This coupe de grâce against my listening pleasure all happened BEFORE 9/11.

To bring this full circle, the GM unit I brought on board did not have any "intentional" local oscillators in it. But I'm sure I'd get the same boilerplate about local oscillators causing interference if I bought one on board. When I did bring mine, it was BEFORE bringing a personal receiver had become an issue. Still, I eventually was asked to shut it off as I was explaining readings to interested nearby passengers who were quite curious. ;)

Jon

One Sievert = 100 Rems if you're old skool. Very roughly, at

30,000ft, you'll get 60 times the dose as you would get at sea level. See the part on "Risk Factor" in the above URL. For continuous exposure, that translates into 60 times the risk of getting cancer. For spending 8 hrs per day at 30,000ft, it would only be 20 times the risk. This takes the glamour out of solving the real estate problem by living in an aerostat.

However, hiding in an underground cave may not help because underground structures tend to accumulate radioactive radon gas (from radium decay), which is a major cause of lung cancer (20,000 deaths per year).

When you get into otter space, you're dealing with x-ray, proton, and electron fluxes: X-rays are in watts per sq-meter, while particles are in particles per square centimeter per second per steradian That makes comparisons with the terrestrial micro-Sieverts per hr impossible.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

I just checked my notes from 20 years ago (when I did this.) Had to go look for the notebook. My memory is exaggerated. I got a little over two orders of magnitude increase, not over three orders as I just stated. It was several hundred times greater than what I measured at sea level before taking off.

Still impressive, though!!

Jon

SNIP

Not to mention the water hazard! :-)

Sorry, but I'm otto bad puns at the moment.

In about 1976, I was diving in Monterey Bay near Monastary Beach. My dive buddy's idea of fun was to poke at a sleeping otter with a stick. Eventually, the otter became irritated, dived under us, and on the ascent, bit me in my posterior through my wet suit. After that experience, I advocate that all otters should be launched into otter space.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

If you don't own a Geiger counter, you may be able to get a reading cheaply from those who do. Just spend a couple of bucks on a ticket for your local public transit system:

Although I must admit that the above is only one data point. It would be interesting if more people who have had similar medical procedures made a point of taking the subway (or equal) home, to see if that happens every time.

Somewhat related: This chart

attempts to give some scale to the amount of radiation produced from various sources, from "eating one banana" to "chest CT scan" to "ten minutes next to the Chernobyl reactor core". There is some discussion of it at . The chart was first published after the Fukushima Dai-ichi power plant meltdown.

Matt Roberds

Yikes, it looks crowded out there!