JG1UPS

再びサンディエゴのハムラジオアウトレットへ行った。ここへ行くと，どうしても何か購入してしまう。1.8MHz帯～440MHz帯まで対応のMFJ-269をゲット。399.95米ドルでカリフォルニア州消費税が8.75%だったので，1米ドル85円換算だと36,970円である。日本でも人気のある製品だと思う。アマチュア無線らしく，取扱説明書の自主制作版 日本語訳 もいくつかネットに公開されているので，とても助かる。日本へ個人輸入した 体験記 のブログもある。

I visited the SENGOKU-TUUSYOO in Akihabara, and about to purchase some tiny electronics parts. I found the Geiger-Mueller counter kit. I decided to purchase it even it was 14800 yen, because I have been expecting study about this area of technology. The GM tube is "CK1026 by Raytheon" that is 50 years old tube. I wonder it is a dead stock though. This is a simple design of GM counter. DC-DC converter produces 1 kV from 3 V of battery for a few second and charge in the 0,1 micro F capacitor. The capacitor apply 1 kV to GM tube. The output of GM tube is connected to the base of transistor that on and off the piezo buzzer. The output of GM tube is also connected to the other base of transistor that drives counter unit. This simple GM counter counts pulse that means Count Per Minute (CPM), therefore you can convert CPM to micro Sv/h by multiply 0,00833. It is just a rough indication because the original information is just a count. I measured the CPM on my dining table. It was 20...