Choosing a Vintage Geiger Counter

Many of us find ourselves in the market for a vintage Geiger counter. Like radios and other gear, they have a pleasing, well-built charm.

vintage Geiger Counter CDV-700

Electro-Neutronics CD V-700 with alpha-sensitive end window probe. Licensed image courtesy of Bullet308

While vintage Geiger counters can be very appealing and economical, we do need to a) keep them running and b) get out of them whatever total functionality we truly require. You may be surprised to find out that even the most basic, old Geiger counter can have its headphones output routed into a modern Windows device to digitally convert and log data! We provide that free software in the links, further down.

Advanced Needs vs. Standard

Two categories emerge in our deciding on the best vintage Geiger counter. We’ll call them Advanced and Standard. We’ll get Advanced out of the way, first, because the majority of this article focuses on the advantages of a particular model well-suited for Standard needs for a number of reasons including community support – the CD V-700 (see Standard, below). More is not necessarily better unless you need it.


If we were looking to hook up, drive, and interpret findings of advanced probes like a gamma scintillation probe (a special, amplified probe that can detect very faint or distant traces, as for longer-range prospecting), then a good Ludlum unit for an acceptable price would be up our alley, such as the Ludlum 3 (most of their models that accept an external probe are full-featured units). Ludlum units are very reliable, seemingly made with above-average components, because we find them working fine, without ever having been refurbished (maybe due for calibration), for decades. They are also equipped with advanced features not required for basic readings for typical, exploratory hobby purposes.

Vintage Geiger Counter

Even with the basic, insensitive beta/gamma-only side-read probe, this Ludlum 3 sold on Ebay for well over $600 by seller “my_brain_fart”

For these reasons, it’s usually difficult to find a Ludlum Geiger counter in reliable shape for less than $350, at best, if not much more ($700 or more is common for a nice one) – and be careful of condition, as probes are particularly easily damaged or contaminated. They’re also more complicated and tightly packed with parts if you’re considering working on one inside.

We’re planning a Ludlum for outdoor prospecting, to use to find outcrops at a distance with a scintillation probe, and then approach with our more standard Lionel CD V-700 or Victoreen 493 after we get closer to the right rocks (at which point a scintillator would be overloaded with excess signal). There are other good brands like Bicron, Johnson, and others (even fancy desk units called scalers) but that’s for another article. The Ludlum 3 or similar gets our Advanced vote for Vintage Geiger Counters and is on our 2022 wish list. It’s so popular they still make a similar version of it.

→ Standard ←

The CD V-700 !

When we’re looking to buy a (another) great-looking vintage Geiger counter, we’re looking to save money, and we are using a standard Geiger–Müller probe (possibly even relatively sensitive ones) then our hands-down winner is the CD V-700!

CDV-700 Geiger Counter


Our refurbished Lionel CD V-700 (left) is very similar to our stock Victoreen 493 (right). We may put the end-window probe on the V-700, recalibrate it, and refurb the Victoreen later.

The CDV-700:
Were produced (and still exist) in countless number
Can be found very inexpensively
Are easy to repair, as they are simple and spacious inside
Can be modified and upgraded in numerous, well-documented ways
Have considerable technical information available for them
Have plenty of compatible parts and even prefab assemblies available
Are a real piece of world history, connected to Civil Defense

Numerous versions of the CDV-700 were made by a number of companies for Civil Defense issue. Usually colored yellow and emblazoned with the cool, Civil Defense “CD” logo, they were made by the thousand by companies including Lionel, Anton, Electro-Neutronics, and Victoreen.

CDV-700 Vintage Geiger Counter

They are similar in general design to the Ludlum 3 discussed., but would require an inordinate amount of work to adapt to scintillation probes or to accomodate advanced adjustments and functions.

The CDV-700 does employ a standard 900v power supply which will run many, typical probes, anywhere from the stock, side-read, gamma/beta “hot dog” probe, to a thin mica end-window probe, to a pancake probe (each example increasing progressively in sensitivity from first to last). Geiger counters require re-calibration if not other minor adaptations if upgraded in this fashion, but it is a straightforward process.

CD V-700 Resources

There are too many makes of the CDV-700 (some with minor internal differences) to to feature them all the manuals here by exact name, but you will have no problems finding the standard literature for yours doing a simple search. The main thing is to seek out not only the primary users manual (usually called “Instruction and Maintenance Manual”) but also, if available, the Shop Manual. This can be more difficult to find but contains more information. The Shop Manual for the Lionel CD V-700 Geiger counter, at least, is below (along with numerous users manuals). Also, it is the authors’ understanding that the Lionel and Anton units are particularly similar.


GeoElectronics CD V-700 Stuff

George Dowell of GeoElectronics is, among other things, a pioneer of refurbishing the CDV-700 (with solid state hardware) as well as modifications and upgrades.

Here he shows how to take an Electro-Neutronics Inc. CDV-700 (dubbed the “ENi”) and use its preferred layout to host the preferred components from the Lionel unit, merging the best of both models into what he calls the “LENi”. He also does various other things like adding a speaker and a built-in pancake probe. You don’t have to intend on doing all of this to get a lot of extra understanding of the CDV-700 Geiger counters with this fabulous article that has been hosted on multiple amateur radio forums:

KFF Homebrew Tips: Geiger Counters in the Ham Shack (at


KFF Homebrew Tips: Geiger Counters in the Ham Shack (at eHam, with comments)

The only sub-link that doesn’t work lately for us is his “Speak2Me” CDV-705 Clone audio module instructions in PDF format, but here is a working HTML copy of that:

Speak2Me CDV-705 Clone Audio Module Instructions

audio module for cd v-700


GeoElectronics offers key parts for the repair, refurbishing, or modification of your CD V-700. You can find two accounts on Ebay, both valid.

The main one seems to be simply:


and the other to try is:


CD V-700... Software?!

One of the advantages of modern (but sometimes joylessly plastic) radiation meters is that they can log data and save the record digitally. Believe it or not, you can do this with the CD V-700 or any other Geiger counter that sends clicks out of an audio jack, using Windows freeware called CDV Counter! We just tested it in Windows 10 and it runs fine!

CDV Counter Freeware for Windows:
SourceForge Download Link for CDV Counter

SciHobby Direct Download:

Buy Radioactive Specimens

You can buy quality radioactive test samples for less money at these fine stores:

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Geiger Check Website

In Closing...

While a Ludlum is on our own wish list for prospecting with a 3-inch-wide gamma scintillation probe (there are some great scintillation probe refurbs and DIY kits on Ebay) we love turning people on to the community support, resources and possibilities still available for the CD V-700 which one may find seriously lacking for many other vintage Geiger counters.