555 Super-Regenerative IF HF Spectrum Analyser

[lordvader88]

I've have all the main parts (I think) and time to make this.
http://www.vk2zay.net/article/256


About the 4 filter inductors used in the input stage. I have some green ferrite core and some yellow ones, they are both bigger than used. IDK the material, they are just generic ones off ebay. They are about 3mm x 8mm, inner diameter is about 4-5mm.

I have 24, 26, 30AGW magnet I think. I made 1 and it was around the right inductance according to my LCR meter. I'm wondering what's more important here.

If I can get the same inductance, with the different wire's and turn numbers, what would make more sense to use ? I should just experiment and see the difference.

Any thoughts? Not much of a question, I'm off to breakfast

[T3sl4co1l]

If they're actually ferrite, I doubt you'll get low enough inductance from a single turn.

Presumably they're powdered iron of some sort (alloy or otherwise).  There are powders good enough here (like the mix #6 used in the original), but not just any will work.  The problem is if you have the wrong type, you end up with more of an RC filter than an LC filter, and your response is drooping off above a few MHz.

So, that also suggests how to test it: apply RF to a few turns and measure the Q.  You've no shortage of RF sources in such a circuit, so you can leave that 'til later and check.

Tim