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Thursday, 15 January 2015

torroids to ID

Anyone got any idea WHAT those torroids are?

Sort of a light purple/mauve colour.

It is the LPF in a RM HLA300 (so not qrp)


Robin G7VKQ said...

I suspect they were old Ferroxcube cores...they used to colour code them and one range has a violet shade. All their cores are now white in colour. I've had their TX36/23/15-4C64 core in violet (I think their pre-white part code was TN36/23/15-4C65). I think the permeability was 125 for the violet range. They also has a pink range (permeability 700) - but your picture looks more violet than pink

M1KTA said...

Thanks Robin... gives me something to start with.



Robin said...

DX-Wire one sold the older purple cores...but the one's they sell now are the newer white coloured equivalents.

There's an old spec sheet for the older coloured versions here -

M1KTA said...


YO9IRF said...

What we know is you can't use ferrite in low-pass filters, the losses are too high and the permeability is anyway too large to get the (small) required values.

Therefore, the cores should be metal powder and judging by the schematic and the number of turns we can see in the photo, I would guess a permeability of around 20 or so (wich is rather high anyway for metal powder, but way too low for ferrite). You can get a pretty good idea by simulating the filters in a software such as ELSIE and tweaking the coil values until you get a response that suits the application (because you know what filters are used on what bands), then count the number of turns in the picture (they are mentioned in the schematic as well :) ) and deduce the permeability. Then you have size, color, approximate permeability, metal powder => much easier to identify exactly.