Super-tiny ferrite rods anywhere?

It sure does :-)

Not yet. My experience with large companies is that they wave off the minute you want baked potatoes instead of fries with that.

Yeah, we can use other materials but they all come with a penalty. Generally in the form or less or much less inductance for the max number of turns we can get on there. We need all the inductance we can get.

How much inductance?? And what frequency range? ">10Mhz" isn't a range; it's a lower limit.

lower limit.

The goal is to get above 5uH. Frequency will be determined by how much inductance we get because the capacitance will be fixed (most likely around 5pF). That's why I wrote >10MHz, because it is unlikely we can get below that. Worst case we'll end up at up to 80MHz. Of course, for obvious reasons we want to really avoid the FM band and also the aircraft band above that. So 80MHz is a hard limit for this case. Lower = better.

Am 21.12.2012 18:05, schrieb Joerg:

Piconics prices are breathtaking.

Mini Circuits comes to mind.

When I was with Infineon Fiber Optics, I said to a MCL sales man that they could sell a bias tee for every ERA-8 or so if the price was right. Seems they listen. :-) Ok, at least the price is better.

BTW a colleague of mine decided not to wait until the Piconics samples were here, put ferrite into a mortar, added epoxy glue and formed some ferrite cores. They were ugly, but his conical coils where surprisingly good.

regards, Gerhard

Am 21.12.2012 18:15, schrieb Joerg: HAve you contacted Fair-rite (or others)?

You might try Würth, also. They have been quite flexible for a friend, even for small runs.

Gerhard

That would be ok in this case. There'd also be other companies I can talk to, such as Gowanda.

Plus we just paid $3 for each 95 gram loaf of German marzipan so we are used to high prices for the good stuff.

But their stuff is comparably large.

Interesting. Maybe I can convince my wife to give me the mortar from the kitchen. But only after the Christmas baking is done :-)

This inductor does not have to be conical and in fact should not be. We have to milk every li'l nanohenry we can get.

Yes, they are good with custom stuff. So is Kaschke in Germany. But these are the "big iron" companies, they are usually not geared for the manufacturing of ultra-small components.

When we did our electronic ultrasound catheters we were told by every high-tech company on the list that it can't be done. Now they are made by the truckload.

Stolen, was it? I used to *love* that stuff. I wish the UK Aldi stores would bring it in for December like they do in Germany.

No, my wife obtained those legally and paid. Come to think of it, we ship them the almonds, they crush them, mix in lots of sugar and spices, and then ship it back at >10x the price. Maybe I am in the wrong business?

Careful, there are major quality differences in marzipan. Some has a cheap sugary taste, some taste almost to die for. The good stuff from Luebeck is really expensive even inside Germany.

BTW, your posts appear as copies in my email. Not a problem but I guess you are one of the guys who have upgraded Thunderbird and must get used to the new buttons :-)

Aldi UK sell some absolute gems from time to time at rock bottom prices. Quality wise they often top consumer surveys when compared with premium brands. I wish they'd open a store in my town!

My ISP is to blame for this, basically. I'll be changing them after the holidays if they don't sort themselves out. I wonder if Aldi's broadband is available here? ;-)

It depends on the density of the ferrite material. If there are air gaps between the grains, it's not going to work very well. Fortunately, it's easy enough to pack the grains with the simple application of brute force. I had to make a custom ferrite bead "extrusion" RF absorber in order to make the FCC happy. I drilled and milled the shape from a block of steel being very careful to include a slight taper over about an 8 inch length. The ferrite powder was produced by beating a torroid core to death with a sledge hammer, and then grinding the residue with a pharmacist mortar and pestle. I eventually had something that looked like black dust.

I forgot what I used for glue. I mixed in some glue, stirred to produce a paste, and shoved it into the slightly wider end of the steel block die. I then hammered it into a solid shape and heated the steel until the glue dried. Flip it over and tap it loose from the narrow end of the die. The first few times, I used too much glue, which caused some problems, but I eventually got the mix correct.

However, there was one big difference between what I was doing and your requirement. Mine was about 6mm wide, while yours is 0.1mm. I suspect the grain size and glue type will be the critical requirements.

Incidentally, I was thinking you might be able to form a tiny ferrite rod using something like the ancient way of making candles, by repeatedly dipping a string into a vat of hot wax. However, I can't seem to think of a neat way to do it with such a small 0.1mm diameter.

Good luck.

snipped-for-privacy@virgin.net Inscribed thus:

Look again ! Our local Aldi and Lidl both have Stollen loaf in ! and Stollen bites too.

If we were dying of thirst in the middle of the Sahara, I might consider drinking Coors. What's their motto? "It's water."

If you wind the coil on a mandrel, some sort of super-tiny (glass capillary?) tube could be used to squirt the loaded epoxy inside. Or just slop it on with a brush.

How thin a wall could a capillary have? They use glass tubes to suck the nuclei out of cells. A thin-wall capillary could be filled with ferrite powder, or ferrite-epoxy to make it a little stronger. Then wind on that.

Some people are making hollow optical fibers. A 120 micron fiber is about the size you need. A kilometer spool of that might last a while.

Now that the Piconics patents have expired, a couple of other people are making the filled conical inductors. Coilcraft and somebody else. They are great for bias tees.

The Italians buy our wheat for a few dollars a bushel, add water, remove the water, and sell us the pasta for $4 a pound.

Coilcraft still wants $20 for theirs. Are the other ones any cheaper?

Cheers

Phil Hobbs

Ours don't have to be conical. In fact, shouldn't be.

How small does centerless grinding go?

I have no idea but it would avoid the risk of breakage by off-axis forces or imbalances.

The French buy our mustard seed for a few dollars a bushel, process it a bit and ship it back at $4 for a few ounces.

Best regards, Spehro Pefhany