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Old 6th Jan 2022, 11:45 am   #1
JHS_Syke
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Default How to replace the coil of YIG oscillator

Hello

I have here an defect YIG tuned oscillator.
The little coil around the YIG sphere is fallen off.

Any suggestions how to fix this??

Joerg
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Old 6th Jan 2022, 4:08 pm   #2
Jon_G4MDC
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Default Re: How to replace the coil of YIG oscillator

Some pictures might help. I think the general opinion is this is probably impossible but please let us have a look.
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Old 7th Jan 2022, 6:54 pm   #3
JHS_Syke
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Default Re: How to replace the coil of YIG oscillator

Here a picture of the coil before it broke off.

It is difficult to see, but the rod is dislocated and off center.

As one can see the coil is bonded.
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Old 7th Jan 2022, 7:13 pm   #4
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Default Re: How to replace the coil of YIG oscillator

What's YIG?

Aub
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Old 7th Jan 2022, 7:15 pm   #5
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Default Re: How to replace the coil of YIG oscillator

I don't think that is one of the windings called 'The Coils' the coarse and fine tuning coils. They'll be in the other half of the casing.

What I think you mean is the coupling loop from the spherical YIY resonator and the amplifier/oscillator microcircuit.

The cylindrical mounting pillar for the sphere is often a PTC thermistor self-regulating heater for the sphere.

With the mount knocked out of position and the coupling loop disrupted, that looks like a device which has had a hard drop.

It could be repaired by someone with the manufacturing fixtures, a new mount and a ball/wedge bonder.

Without these things, I fear you're wasting your time.

David
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Old 7th Jan 2022, 7:17 pm   #6
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Default Re: How to replace the coil of YIG oscillator

Quote:
Originally Posted by Aub View Post
What's YIG?

Aub
https://archive.org/details/wjtechno...p?view=theater

https://en.wikipedia.org/wiki/YIG_sphere

Lawrence.

Last edited by ms660; 7th Jan 2022 at 7:46 pm. Reason: link added
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Old 7th Jan 2022, 7:22 pm   #7
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Default Re: How to replace the coil of YIG oscillator

YIG = Yttrium-Iron-Garnet

It's a crystalline material that has a magnetic resonance which can be in the GHz region, where all the magnetic domains have their axes precessing. Apply a strong DC magnetic field in the right orientation and you can increase the frequency of the resonance. The resonance is a material property, not a function of the size of the sphere.

So that tiny black dot at the end of the white mounting cylinder is a self contained microwave resonator. Moreover it can be tuned across an octave or more by mounting it in the poles of a large electromagnet.

If that isn't enough, the tuning law (MHz versus coil current) is usefully linear.

And on top of it all, the Q it exhibits is quite high.

THe microcircuit in the background carries the oscillator transistor and a few buffer amplifiers.

Drawback? $$$$$$$$!

You're looking at the heart of a good spectrum analyser.

You cn also use YIG technology to make tuneable microwave filters.

David
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Old 7th Jan 2022, 10:24 pm   #8
JHS_Syke
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Default Re: How to replace the coil of YIG oscillator

The device is a YIG tuned oscillator from 2 to 18 GHz. A new one is about 7k$ without tax, toll and freight.

I found a way around for some 100 .
But it would be great to fix it again.

I believe that the YTO had a very hard hit long before I got the instrument.
It was fixed before for shure.
The rod broke of too. But I could fix this. And for a short it worked again!
Then it failed again with an missing coil / loop. There had been 2 windings.

I found a company in germany who can fix it in principle, but the guy is to old now and shattering and me too. I have some ideas how to do it, but no experience in this field.

Any suggestion is helpful.

Joerg
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Old 8th Jan 2022, 5:39 am   #9
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Default Re: How to replace the coil of YIG oscillator

You're lucky that the 2-18GHz nature of the unit is built into the YIG material and the strength of the big magnets.

What you have to fix are the coupling coils.

YIGs using a negative-resistance type oscillator need only one coupling loop/coil. Units using a straight amplifier type of oscillator will have two coupling loops. These will be orthogonal to each other to null direct coupling, but will be in a carefully chosen relationship to the crystallographic axes of the YIG sphere.

Some YIGs have the sphere mounted over one, or a crossedpair of transmission lines, but you won't find these going as low as 2GHz.

To get anywhere, you'll need access the sort of stereo microscope used to assemble hybrid microcircuits, and a wire-bonder.

Find out who made your YIG and search their literature and adverts, you may just hit on a picture of something close.

I've got several YIGs saved here, but none covering that range.

David
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Old 8th Jan 2022, 8:17 am   #10
Cruisin Marine
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Default Re: How to replace the coil of YIG oscillator

Which Spectrum Analyser is it fitted in?
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Old 8th Jan 2022, 12:04 pm   #11
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Default Re: How to replace the coil of YIG oscillator

2-18GHz YIG could be the prime mover in a microwave sig gen or sweeper. Many of them use either dividers or a het band to extend coverage below 2GHz.

Many spectrum analysers cheat by using harmonic modes rather than tuning the LO so widely. Of course the RF preselector filter has to tune right to the top (22 or 26GHz typically)

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Old 8th Jan 2022, 4:47 pm   #12
JHS_Syke
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Default Re: How to replace the coil of YIG oscillator

This YTO was part of a synthesizer. It is used in many roles in this instrument.

I replaced it with a device with smaller frequency range from another manufacturer.
So I can use the sweeper again. Only one option cannot be used.

Usually some people fixed this devices by free hands. all retired now.

I have a little hope to make a supporting struckture and solder a coupling loop made of copper wire in place like smd devices using hot air. By now I have no special idea how to do this.
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Old 8th Jan 2022, 4:52 pm   #13
Cruisin Marine
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Default Re: How to replace the coil of YIG oscillator

2-18GHz YIG could be the prime mover in a microwave sig gen or sweeper. Many of them use either dividers or a het band to extend coverage below 2GHz.

Many spectrum analysers cheat by using harmonic modes rather than tuning the LO so widely. Of course the RF preselector filter has to tune right to the top (22 or 26GHz typically)


Yes I understand that, I have owned 5 speccy's over the years, going back to the old HP 851/8551 washing machines (in fact I had two of those). Those were even before YIG's using a BWO (Backward Wave Ocsillator) from memory.

I ask which unit it came from ,so people can see if they may have a replacement YIG lying about to help the original poster..
There are some articles on YIG repair on the net, here is just one of of them

http://www.kerrywong.com/2014/08/03/...ator-teardown/

This is a nice article on YIG's in pdf format
http://www.vhfcomm.co.uk/A%20Simple%...IG%20Oscil.pdf

Last edited by Cruisin Marine; 8th Jan 2022 at 5:04 pm.
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Old 15th Jan 2022, 12:15 am   #14
Cruisin Marine
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Default Re: How to replace the coil of YIG oscillator

Just to let you all know what you are dealing with, take a look at the end part of this video from about 26 minutes (or even earlier) onwards https://www.youtube.com/watch?v=Pep-cgXjTNo

National Semi produced some info. on semiconductor replacements for YIG's - but I can't seem to find it at the moment. Other manufacturers have done the same, but I dread to think what the cost may be.
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Old 16th Jan 2022, 1:29 pm   #15
JHS_Syke
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Default Re: How to replace the coil of YIG oscillator

At the end of the video it is clearly visible why my YTO failed.

In my case the coupling loop is NOT made of a band, but of two turns of a very thin wire.
In these days a gold covered tungsten wire was used. The bonding joints sometimes corrode and tend to brake off under mechanical stress.
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