Wednesday, September 5, 2012

Radex 1503 review

The Radex 1503 from Quarta is a low end digitally controlled Geiger counter. I acquired mine from annakozub seller on ebay for about 100 euros. It is a very small unit, only 6 x 10.5 x 2.5 cm, very lightweight (90 grams without batteries) and fits perfectly in your pocket. It's perfect if you need something more than a "beeper Geiger".

How it works?

The unit is a pocket size Geiger counter build around the low voltage Geiger-Muller tube SBM20-1 ( located at the left side ) that detects betas and gammas.

Pulses from the tube are processed by a CPU and display them in μSv/h or μRem/h in a nice 3 x 4.5cm graphical display. It can be powered by one or two AAA sized batteries.

The Radex 1503 can be configured using a nice and simple menu based interface. It features a radiation level alarm, audible beeper and backlight.
The specifications from the manufacturer are:

Scale range ambient dose rate equivalent
0,05 ... 9,99
Scale range exposition dose rate
5 ... 999
Range energy scales - radiations
0,1 ... 1,25
(see my note below)
Reproducibility of indications (at confidential probability 0.95), where Ð is a dose rate in μSv/h
Levels of sound-alarm threshold
0.30, 0.60, 1.20
30, 60, 120
Time of calculation
Time of indication
Batteries of "AAA" type
one or two
Time of continuous work of a device, not less
550 **
Overall dimensions
Weight (without batteries)
* The increase in cycles of calculation conducts to increase of reliability of indications.
** Two batteries with a capacity 1350mAh, at a level of a natural background no more than 0,3 μSv/h and with factory settings.

In practice

The unit works fine and is very easy to use. You can power it on or off using the big button on the lower right. After a small presentation, it will start to calculate actual levels of radiation. When you press the menu button, you can access to some adjustment. They are:

Units: You can select to display readings in μSv/h or μRem/h. The unit uses a conversion of 1 μSv/h = 100 μRem/h, so you will read 0.18 μSv/h or 18 μRem/h. The unit uses a sampling period of 40 seconds, and pulses are counts directly on the display, so you can convert your readings to the more comfortable Counts Per Minute (CPM) used by amateurs. If you read 0.18 μSv/h or 18 μRem/h means there have been 18 counts in the last 40 second period, so you can calculate 18 x 1.5 = 27 CPM.

The unit have a great average algorithm. Every time the tube detects a particle, a small back square flashes on the screen (and a beep if it is configured, more later on this). Around this square, you will see some lines.

When the unit starts to count, there are no lines. At the first 10 seconds, you will see two small lines and an extrapolation of that 10 seconds on the display. The unit makes successive extrapolations for the firsts 10, 20 and 30 seconds, making the first complete reading at the 40 seconds. At this time the value can be considered valid.

For the next four periods, new lines will appear drawing a complete square. At this time, the reading is the promediate reading of the four previous readings (this is, 160 seconds). From this point, you will always see a promediation of the last 160 seconds. If counts increase noticeable in one period, a new observing period will be fired. In this way the counter can react to strong variations of radiation levels nicely.

Levels: In the levels menu section, you can set the alarm levels. There are four possible values: Off, 0.30, 0.60 and 1.20 μSv/h ( or 30, 60 and 120 μRem/h ). If readings excess the limit you configured, successive counts will be audible on the speaker. If you set an alarm level, the speaker will remain in silence until the alarm level is reached, whatever configuration you have set on the speaker itself.

Setup: In the setup entry, you can adjust backlight and audio:
backlight: You can turn display backlight on or off. If on, the display backlight will be turned on with a small press on the power button. If it is configured off, it will be never turned on. It is very useful to extend battery life, as we will see later.

Audio: You can turn audio off, high and low. If it is turned off, no sound will be made except if an alarm is configured. High and low refers to the volume of the beep. I have found the low setting to be very loud indeed, so beep can be really disgusting after some time. A small trick is to put some adhesive tape over the speaker. This will turn the beep into one much more comfortable, but I recognize that working at outdoors or in noisy environments, the high setting is very useful. See this mod about this issue.

Where to buy: In this menu entry, the display will show you the international phone number of Quarta-Rad Ltd.

News: In this entry, the unit will show the manufacturer's web ( ) and the unit serial number.


I must admit I'm very happy with this Geiger counter. I have it for about a year now and after many hours of use and prospecting, I will recommend this Geiger counter to anyone. It is a good choice.

It is a step forward the DRSB-88 and the presence of a display, with the counts makes it very useful to measure levels without ambiguity, and the battery life is really impressive.

Don't forget to visit the manufacturer's page of the Radex 1503: and don't forget also to play with the Radex 1503 flash model you will find there!!!

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