EMRFD Message Archive 5237

Message Date From Subject
5237 2010-09-23 18:05:05 Kerry Measurements On Ferrite Materials
Since I am using an N2PK VNA, I've also posted this on the N2PK Group.

I've been doing some tests on ferrite materials and I'm getting some puzzling results.

I've made some test inductors with 15 turns on an FT37-43 and an FT37-61; I'm getting very large values of series resistance and accordingly low values of Q.

The 43 material is worse than the 61 so I've posted two sweeps (of Q and of Rs & Xs) in my VK2TIL Files folder.

Observe Rs values of thousands of ohms and Q of less than one.

It seemed to me that an inductor with that kind of Q wouldn't resonate very well so I added 33pF across it; the sweep of that, also in my folder, shows a nice resonance just where the L & C values say it should be.

For reference I put 15 turns on a T37-6 and swept it; the result, as you can see from another file in my folder, looks as you would expect; low Rs (a few ohms) & reasonable Q (up to ca.150).

Ditto with an air-core inductor (I didn't put this in my folder); it had low Rs & reasonable Q.

Test setup with the N2PK VNA was Reflection mode with a bridge.

Has anyone any advice as to why the results from high-permeability ferrite don't seem right (at least to me)?
5239 2010-09-23 20:27:57 kb1gmx Re: Measurements On Ferrite Materials
5240 2010-09-23 20:56:26 Kerry Re: Measurements On Ferrite Materials
Thanks Allison.

I've just discovered (per Jack K8ZOA) that there is "old" 43 material and there is "new" 43 material; I probably have "old" material which explains, at least partly, why my results differ from those given by Fair-Rite on page 16 of their 16th edition catalogue.

See http://www.cliftonlaboratories.com/estimating_q_of_ferrite_cores.htm

5241 2010-09-24 05:45:23 andres_lu5hah Re: Measurements On Ferrite Materials
Hello, by the way... the N2PK VNA has been bought or built for you? I'm interested to build one them. Or maybe to buy some kit of parts for to assemble. I would be interested on AIM4170 analyzer schematic too. If anybody knows informati
5243 2010-09-24 14:26:48 Kerry Re: Measurements On Ferrite Materials

I built my VNA as most do; there was a ready-built version available (from, I think, Dan M0DFI) but I'm not sure if it's still available.

The website of Paul Kiciak N2PK is the starting point; http://n2pk.com/

PCBs are available from Ivan Makarov; http://www.makarov.ca/vna.htm

Components are available from Digi-Key or Mouser but that's not practical for many countries (like here in VK).

Art Allen KY1K was supplying parts kits; I don't klnow if he still does it. Try aballen@colby.edu or ky1k@verizon.net.

Art also has/had a Yahoo group; http://groups.yahoo.com/group/N2PK_VNA_Group_Buy/

It seems rather moribund at present.

Software is myVNA by Dave Roberts G8KBB; http://g8kbb.roberts-family-home.co.uk/

Beautiful software!

There is a Yahoo group for the N2PK VNA; http://groups.yahoo.com/group/N2PK-VNA/?m=0

Join there and you will get great help.

This is not a simple kit; there are no step-by-step assembly instructions. But I managed to build one; that proves that anyone can!

It's a wonderful instrument; very powerful.

The only minor limitation is the upper frequency of 60 MHz; I've just started building a DG8SAQ VNWA to get higher frequency (1.3 GHz). The VNWA is simpler to build and a full kit, including case, is available from Jan G0BBL at http://www.sdr-kits.net/.

Built instruments are also available from Jan.

See the VNWA Yahoo group; http://groups.yahoo.com/group/VNWA/

Kerry VK2TIL.
5263 2010-09-27 10:00:41 Cash Olsen Re: Measurements On Ferrite Materials
One very useful and well developed Spectrum Analyzer / Tracking Generating
and VNA that was overlooked is Scotty's Spectrum Analyzer

It has the general range of 100KHz to 1000MHz.


Cash Olsen
ARRL Technical Specialist

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