schottkys instead of germanium diodes for crystal radios? - Page 1
Forum section: electronics / rf-microwave

author: ali6x944
author_rank: Frequent Contributor
timestamp: February 07, 2016, 06:37:11 pm
content: schottkys instead of germanium diodes for crystal radios, is it working or a bug I got?

author: alsetalokin4017
author_rank: Super Contributor
timestamp: February 07, 2016, 07:21:58 pm
content: Quote from: ali6x944 on February 07, 2016, 06:37:11 pmI've tried it a few times and they can work OK but germanium is better.Schottky: 1n5711 etc.Germanium: 1n34a, 1n60, etc.

author: Ian.M
author_rank: Super Contributor
timestamp: February 07, 2016, 07:37:08 pm
content: Small signal Germanium diodes are usually point contact so have very low junction capacitance. If substituting a Schottky diode you'd specifically need a low capacitance one designed for RF use.

author: Macbeth
author_rank: Super Contributor
timestamp: February 07, 2016, 07:48:10 pm
content: Do it properly with a cats whisker

author: KJDS
author_rank: Super Contributor
timestamp: February 07, 2016, 09:07:44 pm
content: The cheap solutionhttp://www.infineon.com/dgdl/Infineon-BAT63SERIES-DS-v01_01-en.pdf?fileId=db3a304314dca38901151817843c0df4Avago and others do expensive zero bias schottky diodes that may be better, but probably not worth teh extra cost for most.

author: Melt-O-Tronic
author_rank: Frequent Contributor
timestamp: February 07, 2016, 11:01:13 pm
content: Quote from: Macbeth on February 07, 2016, 07:48:10 pmPreferably from an actual cat.But seriously, that comment has the potential to go somewhere interesting.Nevertheless, I'll be looking forward to reading about the OP's upcoming Schottky experimentation . . .

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 08, 2016, 06:28:28 am
content: Anything BAT54 sized or smaller will be perfectly fine, at frequencies well beyond the shortwave range.Tim

author: Ian.M
author_rank: Super Contributor
timestamp: February 08, 2016, 07:10:01 am
content: The problems with using a real cat's whisker are (1) acquiring it, and (2) metallizing it. (1) is a problem because the cat will be naturally reluctant to donate a whisker, your dexterity in cat-proof PPE is likely to be insufficient to pluck said whisker, and you will then have to spend an indefinite length of time nervously watching out for a revenge attack by the cat. (2) is only moderately tricky - you need a vacuum chamber set up for sputtering and a stepper that has been stripped, degreased and re-lubricated with a vacuum safe lubricant then out-gassed at elevated temperatures under vacuum to rotate the whisker to get an even coating.Combining the steps is not advisable unless you don't mind writing off both the cat and the vacuum chamber.

author: Gribo
author_rank: Frequent Contributor
timestamp: February 08, 2016, 09:06:27 am
content: The HSMS285 can be used, if your sensitivity requirement is not that high (It can reach -57dBm). It is available in SOT363, which is not so difficult to solder. I like the cat whisker idea, mine are passive enough so it might even work without too much trouble

author: alsetalokin4017
author_rank: Super Contributor
timestamp: February 08, 2016, 11:04:07 am
content: Heh.... I guess I'm lucky... I found a cat that had whiskers made from phosphor-bronze, like the wrappings of a guitar e-string. This is an ideal material for use with lead-galena crystals in an actual crystal radio.

author: Melt-O-Tronic
author_rank: Frequent Contributor
timestamp: February 09, 2016, 06:26:50 am
content: alsetalokin4017, looks like we're in the same area.