[Swlug] DIY Geiger counter

[Alan Gray]

B331 and F.Job do not seem much help. Unfortunately that means you have a mix of   characteristics. It can vary a lot.

It isn't just the material properties at extremes, but the variation between visually similar products due to manufacturing choices. A good example  are ceramic disc capacitors. Some are very poor at RF frequencies. You cannot tell by looking.

These matters are important throughout, but at the beginning of the chain, with such weak signals, they are critical. Look at any front end RF circuit and you will find mica capacitors dominate especially in the signal line.

Regarding the transistors. These switching types easily handle currents of hundreds of milliamps. They do this by having physically large substrates/junctions that aid heat diffusion. The downside is that it introduces more capacitance. Look at small signal RF types and usually they handle maybe 5ma.

Regards
Alan Gray 



On 12 March 2025 15:38:18 GMT, Rhys Sage via Swlug <swlug at mailman.lug.org.uk> wrote:
>I had a few minutes so I went and had a look at the transistors. Mysteriously, half an hour vanished.
>
>My BC547s seem to have B331 marked on them.
>My BC517s seem to have F.Job marked on them.
>
>I understand what you mean about things having more interesting properties at the extremes of use. At one time I was interested in building a high-voltage microflash. I researched that and got myself a copy of the handbook of Chemistry and physics. That revealed interesting conductivity properties of various normally non-conductive materials. I do have a half-completed microflash that's designed for low voltage use. That just needs a fast transistor capable of switching 200 white LEDs on and off in 1/250,000th of a second.
>
>Rhys Sage
>
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