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If you can, I have a full bin of unknown ferrites waiting for classification ;)

True, but probably not so much that you can't come up with a quick way to identify them. 20% variation probably doesn't move it to confuse with a different mix. When I get some time this weekend,

VERY helpful; thanks! I think I am half-way there as I have put a coupling coil on my tuning inductor so the antenna signal goes through only that, with about 15% as many turns as the inductor. On the

Yes, it's my experience too that the crossover point of reactance and resistance varies a lot between batches, also between cores of different sizes made of the same material. Determining it is also

Andy, with your crystal radio something similar happens as I described in my post, about the low pass filter. Your radio's tuned circuit is loaded both by the antenna and by the detector+headphones.

There are huge variations in ferrites, parameters of the same model from different batches can vary greatly. [email protected]> wrote:

Andy, An interesting discussion of Q at LF/MF frequencies >> https://rudys.typepad.com/files/optimum-inductor-l-d-ratios-1.pdf There are many "crystal radio" groups on Faceb

Manfred Mornhinweg, Excellent post. Thank you Roger

To start Ebay has plenty, look for mak1939. He also carries the R40C1 toroids and rods. You can easily get Qs over 1000 with his toroid and litz. Here is mak's Ebay site, The second thing to try is

One method is to find the frequency where R and X cross. That corresponds to where the complex permeability values μ′ and μ″ cross and is unique to each ferrite Mix. Roger Roger

It occurs to me that one could write a software application, either on a host computer, or as alternate firmware for the NanoVNA that would work as a "identify the mystery toroid". Run a couple turns

In AM BCB applications, a bar core with a lot of turns is often used to be more compact. Hard to fit that clorox bottle in your pocket, after all.? Since the signals are strong, background

Thanks, Manfred, this is incredibly helpful to a totally novice crystal radio builder! I see that low permeability is best for my application, which greatly reduces the “advantage” of needing very

Engineering is the art of finding workable compromises. Let's leave perfection to the philosophers. When a electronic engineer needs an inductor in a circuit, it would be really rare that the

I have also used them as inter-stage transformers. They make great broadband transformers between stages or devices. 73, Zack W9SZ

Ferrite cores are used for RFI suppression chokes, where we *want* losses. 73, John W1JA

Go to the Micrometals web site. Take a look at their various mix of iron powder cores. You can mix and match size, L and perm values to see what Q is achieved. Unloaded Q value excess of 400 is quite

Use a different core, litz wire is useful up to about 3MHz, higher than that it provides no benefits. [email protected]> wrote:

It is as simple as the ferrite material you have is very lossy. There are much better ferrite materials to use at 1Mhz. With a proper core and litz wire, you can get the R under 1 ohm.