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Old 20th Mar 2019, 2:17 pm   #1
Wendymott
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Default T50-6 Torroid cores

Hi Peeps. In the homebrew section I have posted a query re my HF LP Filter. These use T50-6 torroids. The 80 and 40 metre filters are ok with low insertion loss and a good cliff edge fall off.... however the 20 metre filter is giving trouble..I purchased a number of T50-6 torroids from China. It seems that these cores may not be what I thought I purchased, yes they are Yellow, the correct size, but I have an idea they are mis labelled.
How can I check... The turns / uH seem to be a lot lower. say 5 turns = 1uH where as the inductors quoted in my data sheet quote 15 turns = 0.9 uh.
Obviously with less turns the "Q" factor will be less, thus the probable reason why the filter cut off is poor.
Your comment are welcome.
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Old 20th Mar 2019, 11:17 pm   #2
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Default Re: T50-6 Torroid cores

Quote:
Originally Posted by Wendymott View Post
I purchased a number of T50-6 torroids from China. It seems that these cores may not be what I thought I purchased...
How can I check... The turns / uH seem to be a lot lower. say 5 turns = 1uH where as the inductors quoted in my data sheet quote 15 turns = 0.9 uh.
I would wind ten turns, evenly spaced around the entire core, and measure the inductance, and compare with a known genuine one with an identical winding.
Buying stuff from suppliers in China is a lottery, you never know what you are going to get.


Note also that the inductances listed in the usual tables assume the turns are evenly spaced around the entire core. This can catch people out when following instructions in published designs. "Wind 15 turns on a Txx-x" , without specifying if they are close wound in one sector or evenly spread, can lead to all sorts of trouble.
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Old 20th Mar 2019, 11:18 pm   #3
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Default Re: T50-6 Torroid cores

Hi Wendy,
Do you still have your Rigol spectrum analyser and tracking generator?

One way to check the Q (and the inductance at 14MHz) is to connect the 0.9uH inductor in series with about 150pF (use 47pF x3 in parallel to make up the 150pF).

This should be resonant somewhere around 14MHz. Then you fit this series resonator as a shunt component across a pair of back to back connectors and then you set the analyser to sweep across maybe 0-25MHz and then zoom in on the notch. Then measure the depth of the null/notch and the notch should be somewhere around 14MHz with a genuine T50-6 core. The deeper the notch the better the Q but you need to use decent low loss caps and I'd recommend using 3 ceramic 47pF in parallel to get 150pF with a low ESR.

I'd expect a 0.9uH T50-6 toroid to have a Q of over 250 at 14MHz if it is wound with thick wire. So I'd expect the notch to be about 38dB deep if the Q is 250 at 14MHz. I'd expect the notch to be about 33dB deep if the Q is only 150 at 14MHz.

IMPORTANT!!! To prevent confusing errors in the test setup you should fit a pair of 10dB attenuators inline at each test port before you normalise the response to 0dB when calibrating without the coil connected. This is to improve the accuracy of your 50R test ports on your Rigol analyser. They won't be exactly 50 ohm and so the attenuators will improve this and this will minimise the overall uncertainty of the test.

If the notch is a lot shallower or if it is nowhere near 14MHz then there's something wrong with your T50-6 toroids. They may be fakes.
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Old 20th Mar 2019, 11:26 pm   #4
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Default Re: T50-6 Torroid cores

There are a lot of duff ones out there. I usually buy from GQRP club or spectrum communications. I’d be tempted to chuck them and buy some new ones.

Incidentally RS sell all the material 43 cores for considerably less than anything labelled FT!
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Old 20th Mar 2019, 11:39 pm   #5
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Default Re: T50-6 Torroid cores

I buy mine direct from the UK distributor for Micrometals. The last time I did this the UK distributor was Powermagnetics.

http://powermagnetics.co.uk/pace-magnetics.html

They seem fine with fairly small orders but I'd recommend buying a lot of toroids over various sizes to make it worthwhile. Each toroid type will be delivered in its own labelled grippy bag with the POWER logo on it. So I know which ones I have here are genuine Micrometals toroids. I still have some that I bought on ebay and from Jabdog and I try and keep these away from the ones I know are genuine from the UK distributor.

I have seen differences between genuine ones and my ebay clones but nothing major. However, there will almost certainly be fake ones out there that will be totally duff.
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Old 21st Mar 2019, 7:59 am   #6
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Default Re: T50-6 Torroid cores

Hi Wendy, send me a reminder if you need some when I'm back home next week and I'll see what can be found; I have a good selection of Micrometals cores.

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Old 21st Mar 2019, 1:58 pm   #7
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Default Re: T50-6 Torroid cores

Hi Peeps.. Many thanks all for your comments... Jeremy.. Yes I still have the Rigol. I will certainly do those tests this PM...
Thanks for the offer ED...until I know what I have got..I will keep your offer on the back burner...
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Old 21st Mar 2019, 2:10 pm   #8
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Default Re: T50-6 Torroid cores

Hi Peeps.. back again.. Lesson 1....Buyer beware...that incredible bargain....absolute rubbish..
Jeremy... I have tested the purchased cores and the originals from Minikits when I bought a dual switched filter... The results are below
Obviously the Chinese cores are probably made of sawdust..
I am not upset about the purchase.. but I am mad about the wasted time and effort to get a filter working that should have taken 30 mins.
Thanks Jeremy....... in future I will test my cores before I try and use them.
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Old 21st Mar 2019, 2:17 pm   #9
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Default Re: T50-6 Torroid cores

Off topic (sorry) but is that a DSA815-TG? If so, any comments on it? I have been considering buying one for about 6 months now but haven't found any objective information really.

I missed a new in box one without a tracking generator that someone sold buy it now on the usual auction site for £400 a couple of months back - literally they got to the checkout before me
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Old 21st Mar 2019, 2:18 pm   #10
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Default Re: T50-6 Torroid cores

I just ordered X10 50-6 from power magnetics.. delivery friday.
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Old 21st Mar 2019, 2:30 pm   #11
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Default Re: T50-6 Torroid cores

Hey Mr Bungle.....DSA8215T....... BUY IT !!!!.... Ok there may be better Spectrum Analysers on the market... but VFM.... WOW..... If you look on Youtube.. there are zillions of users, applications etc... and that annoying aussie that tests items..what is it with that guy ??enthusiasm... I guess.
But if you have the funds get one. There are some digital upgrades that if you buy from the importer cost a fair "wadd" but I downloaded mine from somewhere to make the VSWR measurements... The adaptor cost a fair bit too.. so I made my own.
To be honest... buying the item WITHOUT the tracking generator is like buying a car without the engine... I use the TG nearly everytime I use the equipment
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Old 21st Mar 2019, 3:31 pm   #12
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Default Re: T50-6 Torroid cores

Yes, those Chinese T50-6 toroids look like they could be made from dried custard

Powermagnetics have been the UK distributor for Micrometals for decades and a few years ago at work I requested samples direct from Micrometals in the US because I'd been getting inconsistent results from some yellow 6 mix toroids. They didn't look right and it turned out our buyer had used the grey market instead of the official distributor. Micrometals then passed my query on to Powermagnetics and they kindly sent me a reference sample of every toroid mix and size that I'd enquired about.

You can see below on the Micrometals website that Powermagnetics are the official UK distributor. I doubt Powermagnetics would tarnish their 20-30 year old history with Micrometals by stocking alternative versions of these toroids so I think they are a reliable source.

https://www.micrometalsarnoldpowderc...d-distributors

I now mark every genuine toroid with a little 'MM' logo with a black permanent marker as I take it out of the bag. This means that if it ever gets reused in the future I will always know that this toroid was genuine from Micrometals. I put a 'J' on the Jabdog ones and and an 'E' on the Ebay ones.
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Old 21st Mar 2019, 3:42 pm   #13
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Default Re: T50-6 Torroid cores

Quote:
Originally Posted by Wendymott View Post
Hey Mr Bungle.....DSA8215T....... BUY IT !!!!.... Ok there may be better Spectrum Analysers on the market... but VFM.... WOW..... If you look on Youtube.. there are zillions of users, applications etc... and that annoying aussie that tests items..what is it with that guy ??enthusiasm... I guess.
But if you have the funds get one. There are some digital upgrades that if you buy from the importer cost a fair "wadd" but I downloaded mine from somewhere to make the VSWR measurements... The adaptor cost a fair bit too.. so I made my own.
To be honest... buying the item WITHOUT the tracking generator is like buying a car without the engine... I use the TG nearly everytime I use the equipment
Thanks for the positive review and motivation! I've already got a couple of Rigol items which I'm rather satisfied with so I may see if I can sneak this one in without approaching the purchasing department (MrsBungle)

I've actually already built a return loss bridge which is good to around 80MHz (fine for me) so that would be handy. I'm using it with an AWG and W7ZOI power meter at the moment. Tracking SA would make my life considerably easier there!
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Old 21st Mar 2019, 4:28 pm   #14
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Default Re: T50-6 Torroid cores

Hi guys...All noted. Thanks for the comments... I will report back when I have the new cores.
Dont forget Mr Bungle..a bit of "lubrication" in the buying department works wonders,,flowers, chocks, etc.
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Old 21st Mar 2019, 4:34 pm   #15
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Default Re: T50-6 Torroid cores

She's diabetic and suffers from hay fever so I'm screwed there

Good luck - hope your LPF works out
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Old 22nd Mar 2019, 5:03 pm   #16
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Smile Re: T50-6 Torroid cores

Oooppps.. well I am sure you will think of something..the DSA8127T is well worth the effort.. good luck
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Old 23rd Mar 2019, 12:01 pm   #17
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Default Re: T50-6 Torroid cores

Morning peeps. Micrometals torroids arrived. Tested OK. It is quite obvious that the counterfeit items are visually different.. in as much as the base core is of white material. The genuine cores are black.. see photo.
Now I can continue with the project... and return the snide parts to the supplier.
It will be interesting to see what turns up next week.. I bought another 10 from an Ebay source.
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Old 23rd Mar 2019, 1:53 pm   #18
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Default Re: T50-6 Torroid cores

Interesting. Probably SMPS parts that looked about right.
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Old 23rd Mar 2019, 5:33 pm   #19
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Default Re: T50-6 Torroid cores

Yes, the yellow/white one is probably a different part rather than a fake. So the seller has advertised them incorrectly.

I have a few ebay sourced T50-6 cores here and quite a few Jabdog ones too. This morning I compared them to a genuine MM core under a microscope and it was easy to spot that the Jabdog ones were visibly different. I don't quite have perfect colour vision but it was easy to spot that the Jabdog ones are a deeper yellow colour and the coating finish is different with more of a lumpy orange peel look. The Jabdog core width was about 0.1mm narrower but otherwise the same.

The ebay version looked identical to the genuine one even when zooming in and looking for tiny differences. The dimensions were the same too. I could not tell them apart with a critical visual inspection and this was in terms of colour, coating finish and overall dimensions.

So I was hopeful that these ebay ones were genuine. However, when I did a Q test at 14.5MHz the Jabdog version came out on top. It managed a Q of 316 and the ebay version only managed 270. The genuine version measured about 310 a few days ago. So not much in it.

So it's hard to conclude much from all this. I don't know how much variation there is between batches of genuine toroids in terms of Q or paint colour/finish. The Jabdog version looks different in terms of colour and surface finish but it could still be a genuine part from a different batch? The Q was fine and the inductance was spot on (at 14MHz). So I would be happy to use them here at home. They could all be genuine for all I know. However, I did have some ebay '6' toroids a while back that had a completely different Q curve to a genuine toroid. I'll have a look at all three of these toroids later today on the VNA to look at Q vs frequency. I think they will be very similar but I won't know until I do the tests.
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Old 23rd Mar 2019, 6:28 pm   #20
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Default Re: T50-6 Torroid cores

Just a point with Amidon stuff as well. Most of it is from the same suppliers as the random crap from China. They just sampled the batches and stuffed their own classification over the top. They aren’t really that good. Just common.

I’ve been buying a lot of cores elsewhere these days. For example if you want an FT37-43 you can pay through the nose for a few branded or grab 25 of them for £2.80+VAT off RS under Fair Rite 5943000201. And they are actually fair rite ones not lookalikes from the lowest bidder. I bought some FT43-82 cores off RS as well. Think it was £8 for 20 of them. They’re going for £12.50 for 5 on eBay!?!?

I’m still trying to work on suitable toroidal cores that are for tuned circuits rather than transformers and chokes however.
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