Tip for crystal set builders.

[catman]

G'day all, well crystal sets are antique! Just a tip for anyone building one with 'modern' diodes, genuine germanium diodes are getting increasingly hard to get (at least in this country), although the silicon schottky 'equivalents' aren't bad at all (e.g. BAT46), and simply by putting several in parallel, one ends up with a much better 'single' diode with reduced 'turn on voltage' and negligible reduction in back resistance 'leakage'.

You can't do this with genuine germanium diodes as the 'back leakage' considerably worsens. I use four BAT46's in parallel in my crystal set and the performance is much better than a single diode, especially with weak RF signals. Regards, Felix (vk4fuq) aka catman.

[old_tv_nut]

Interesting - thanks for that.

[Celt]

Felix, how many grouped together work best? Four?

[catman]

G'day mate, there may be a practical limit in number but I am presently using four BAT46 schottky diodes in parallel with good results, in fact I am listening to the cricket with it now on local AM radio.

As an example of what paralleling four BAT46 diodes does, one BAT46 has a turn on voltage of about .24 volts. Four in parallel measures .205 volts. Regards, Felix (vk4fuq) aka catman.

[VTVM]

In the USA, I get new IN34A's 50 or 100 at a time from eBay...Good to know the schottkys work though.
It's also fun to make zinc oxide/ lead detector diodes. They perform just as well as germanium and are pretty easy to make and adjust at home. Far easier than the old steel wire catswhiskers to get adjusted to to point where they are working well.

cheers
Rob

[old_coot88]

You guys should check out this site (if you haven't already seen it)..

http://www.sparkbangbuzz.com/

[VTVM]

^^^ Yep. Great site. That's how I learned to make my own solid state detectors. Check out the flame triode part, too.