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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 23rd Mar 2019, 7:56 pm   #21
G0HZU_JMR
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Default Re: T50-6 Torroid cores

Yes it pays to shop around and I try and buy most of my stuff from Farnell, Mouser or RS. I did have a go with the VNA this afternoon and I compared the genuine MM toroid against the Ebay toroid and also the Jabdog toroid. I tested all three in turn on the same jig and I adjusted each one for 800nH at 14MHz. I then took S11 data and compared all three using Genesys.

The official Micrometals software predicts that 13 turns on the toroid will have a Q peak at 17MHz and the inductance will be around 800nH depending on how the turns are wound. I wound them all with the same wire and made sure the windings looked the same.

See below for the results for Q vs frequency as tested by the VNA. As expected, the Jabdog version just comes out on top with the red trace. The pink trace is the genuine MM toroid and the black one is an unknown ebay version. Both the genuine toroid and the Jabdog one show the Q peak in the right place at 17MHz. However, the ebay version has a lower Q peak and the peak is at a lower frequency. I did try even spacing or uneven turn spacings on the ebay version but it always gave the same Q curve when adjusted for 800nH. So even though this one looks identical to the genuine toroid I suspect it may be a counterfeit version.

The VNA is really being stretched when making this measurement and that is why the data is noisy on each trace. This isn't a reliable method for measuring Q but I think it is OK when doing comparative tests like this, especially when the other test methods agree.

There's also a plot of inductance vs frequency and all three seem to agree very closely up to 100MHz.
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Old 23rd Mar 2019, 8:18 pm   #22
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Default Re: T50-6 Torroid cores

Interesting results. Thanks for taking the time to write them up.
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Old 23rd Mar 2019, 9:42 pm   #23
G0HZU_JMR
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Default Re: T50-6 Torroid cores

Glad it's useful info I also compared an 800nH inductor made from a red T50-2 core from the same ebay vendor against a genuine T50-2 from Micrometals. See the plots below.

It shows a similar issue where the Q of the ebay toroid is lower and it peaks at a lower frequency. According to the Micrometals SW the Q should peak at 11MHz for this 800nH inductor when made from a T50-2 core.

The genuine T50-2 toroid shows a higher Q peak that is at about 10MHz but the ebay version is definitely different because it peaks a couple of MHz lower. It would still be a useful inductor but I'm not sure this is a genuine Micrometals T50-2.
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Old 24th Mar 2019, 1:34 am   #24
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Default Re: T50-6 Torroid cores

Hi Jeremy and Mr Bungle...
Yes, the yellow/white one is probably a different part rather than a fake. So the seller has advertised them incorrectly.
I looked at the supplier of my cores and surprise surprise.. he is out of business..
I will wait and see if he refunds me..
It seems that this torroid business is more complicated than first thought..but initially the results are now as I need them..I am quite happy now that the filter works correctly, although it needs a slight tweek.
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Old 24th Mar 2019, 2:11 am   #25
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Default Re: T50-6 Torroid cores

Quote:
Originally Posted by MrBungle View Post
I’m still trying to work on suitable toroidal cores that are for tuned circuits rather than transformers and chokes however.
On the 'toroid ring' page at RS, use the filter on the left side of the page -> Brand -> Fair Rite.

That will give you the inductor ones (all the others EPCOS, Wurth, TDK etc are mainly EMI suppression stuff)

Very limited range though.
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Old 24th Mar 2019, 10:51 am   #26
MrBungle
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Default Re: T50-6 Torroid cores

Yeah have been doing that. Most of them are Material 43.
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Old 24th Mar 2019, 12:19 pm   #27
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Default Re: T50-6 Torroid cores

The T50-6 sort of cores are dust-iron and made by Micrometals inc. of Anaheim California.

FT43- cores and material 43 usually refer to ferrite material number 43 by Fair-Rite inc. of Wallkill New Jersey.

For RF resonators, tuned circuits, filters you want the powder-iron cores. Ferrite ones make good transformers. For tuned circuits you need gapped ferrite cores and materials like number 43 is used to a couple of hundred kHz in gapped cores. As a transformer, number 43 is good across the MF and HF bands. Above 100MHz, it does great service as an RF absorber.

All sorts of makers colour code their parts to show which of their materials they used. What yellow means could be anything if you don't know the maker.

When I designed the dual directional wattmeter for George Dobbs, (Sprat 61) I used a material equivalent to 43 made within a couple of miles of his vicarage. S2 material from SEI. It happened to be yellow coded. The folk at SEI made superb cores, capacitors and crystals, they were friendly and their prices were attractive.

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