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Building a Colpitts

Building a Colpitts

Building a Colpitts

(OP)
Hey guys, when it comes to EE I am the epitome of a novice. In fact, I picked myself up a experiment lab from Radioshack the other day to learn some basics. Unfortunately the superiors at work need me to develop a colpitts oscillator that oscillates at 13.46MHz. I was wondering if anyone had any pointers. I'm most confused about which components are necessary to acheive this result.

Thanks in advance.

RE: Building a Colpitts

Hiya-

ARRL handbook will go into detail.  Available from any library.

Computer guys (confuser) guys designing a colpitts oscillators. Scary stuff!  Hope that Fox Charlie Charlie will not get involved with this!

RE: Building a Colpitts

(OP)
My boss is a bit of an inventor/entrepreneur. He's pretty successful at what he does. Now-a-days he's leaning towards achieving efficient over unity. This oscillator is necessary for the project we're working on.

Unfortunately, considering how most physicist feel about the theory of over unity and how it plays into our current understanding of the science, he refuses to invest in seasoned veterans. Furthermore, I doubt he wants to employ an EE for the sake of building one oscillator.

So now I have been burdened with the task of building it, lol. How fortunate (sarcasm).

RE: Building a Colpitts

Over unity resides at 13.46 MHz - who knew?

winky smile

RE: Building a Colpitts

I'd assumed an xtal would be used.

RE: Building a Colpitts

(OP)
Well... this is more along the lines of WTP than it is OU. We're following the MIT model. Sorry for the confusion.

RE: Building a Colpitts

A crystal, a schmitt trigger, some caps, a resistor, and a voltage source... that should about do it.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Building a Colpitts

(OP)
Thanks macgyvers. I mean, I managed to get a general schematic for the Colpitts oscillator. I was hoping I could get some detailed specs on each component without having to work out the frequency/LC equation. Looks like I may have to do it anyway.

I'm off to borders to pick up an ARRL handbook for further reference. Thanks for the help guys.

RE: Building a Colpitts

Another suggestion... look at the clock section for a lot of the smaller micro-controllers out there.  they typically have some useful component values, and the tech notes from the same companies will also have useful app details.  These would at least give you useful starting values for 2/3rds of the components.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Building a Colpitts

My 1989 ARRL handbook (page 10-1) has a schematic of a Colpitts oscillator that uses a xtal and a 2N2222 and all the other components (R and C) are not frequency critical.

I obviously don't know all of your requirements, but it is not likely that you want an LC-based oscillator.

RE: Building a Colpitts

(OP)
Oh, well Borders didn't have any ARRL handbooks in stock so I put one in order. I guess I'll wait for that to come in at the end of the week.

VE1BLL, is that so? My understanding of all Colpitts oscillators is that a few of their components' values are frequency dependant (especially the capictors). Then again, I know the least bit about electronics. But that's what I gathered from Wiki.

In either case, I'll try to work out the equation featured on Wiki and see what I come up with. Overwhelming still, It's been years since I've touched Mathematics. I appreciate all the help.

RE: Building a Colpitts

While I'm not trying to discourge you from learning, why would you even entertain the notion of continuing with this project?  Over-Unity machine!  This is an exercise in futility.  Perhaps, you should show your boss a book on physics, and try to explain why this hair-brained scheme will never work.

RE: Building a Colpitts

Well, the Xtal is certainly frequency critical. Hopefully it has "13.46 MHz" stamped into or inked onto the package.

RE: Building a Colpitts

(OP)
Well, it's not discouraging at all. Quite frankly, it's a matter of getting paid or not getting paid. The boss asks for it, I try to do it--whether possible or not.

Ironically, he actually owns a few books on Physics. And he understands the complications that are present when taking the fundamental laws of thermodynamics into consideration. But along with Tesla, hundreds of experimentors who have made positive claims of small scale success, and the mysterious Steven Marks, my boss is quite the believer of free energy.

I guess I can't knock him--considering that some of our greatest revolutions were sparked by radical, non-traditional concepts. But as stated before, I'm just a pair of hands looking forward to pay-day Fridays.

RE: Building a Colpitts

Most curious...
Save your  money as your boss's will surely run out eventually.  Or he'll land in prison for trying to sell some over-unity crap to some gullible mark.

Does sound like you have an interesting job though.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Building a Colpitts

huh, thought the "over-unity" thing was a joke... didn't realize the main in charge was actually asking for something real.

My suggestion, then, would be put down the soldering iron and start searching for another job... your current one is bound to run out of money in short order (assuming the company is based on these over-unity type schemes).

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Building a Colpitts

(OP)
lol...

Our revenue comes in from the other businesses he owns as well as a few of the patents he holds. For the obvious sensitivity issues of his projects, I'll spare throwing his name around--but rest assured, funding is not of major concern to him.

I really don't mean to spark debate of any sort. Perhaps he is nothing more than some looney, wealthy fool. Nonetheless, I find my work with him to be rather interesting and fruitful noless.

All the help is appreciated. And should anyone truly be interested in the OU debate, I'm definitely no legitimate candidate for or against the argument. But head over to overunity.com. There's some pretty interesting stuff going on in those forums.

Thanks again.

RE: Building a Colpitts


Colpitts: do a search for "dead bug construction" - crude but stable.


Cheers

Harry
(G4NTK in another life!)

RE: Building a Colpitts

Try to learn some basics on oscillators from good sources first, then go looking for circuits in Google.
 
Be aware of those DIY sites with RF bugs and spy microphones, often written by non EEs (tech geeks, amateurs, etc.)

Good Luck!
Gonzalo  

RE: Building a Colpitts

Check the frequency. I am pretty sure it should be 13.56 MHz, not 13.46 MHz :)

RE: Building a Colpitts

It's over unity... maybe he wanted to make some contact with it winky smile  a few less kiloHertz should do it...

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Building a Colpitts

Hiya-

Continuing this thread.  Hint.  Get the boss to pay for the ARRL handbook.  When it comes, put YOUR name on it in big bold letters across the top (where all the pages are).  When you leave, due to new job, financial problems, whatever, take the book with you!

  Cheers,
 
    Rich S.

RE: Building a Colpitts

I have liked the idea of putting together a colpitts oscillator. Tried one from a nice description by valdim Manassewitsch and dead bugged a 10 MHz colpitts with a 2222 BJT and passives I had at the office. A small amount time a bit more effort in the calcultations an order to any of the mirad of elctronic distributors a good osicllator could be completed. Valdim's book is called "Frequency Synthesizers: Theory and Design". Would like to discuss the circuitry behind the colpitts a bit more.

RE: Building a Colpitts

If this dynamic and inventive boss and his willing and cluless hand want to build a Colpitts oscillator. Then let them do so.

But do not tell them to use a crystal. That is not Colpitts any more.

I can not understand why the Colpitts is the only oscillator configuration deemed suitable. There are dozens of other topologies. Could it be that the positive feedback obtained in the Colpitts oscillator reminds some creative souls about over-unity? Which it is, voltage-wise, but not power-wise. Then, why wouldn't a Hartley be just as good? It also has over-unity feedback.

Also, by using a tunable ciecuit (lika a Colpitts) they may be able to find that sweet spot somewhere between 13.46 and 13.56 where the pot of gold resides.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Building a Colpitts

"But do not tell them to use a crystal. That is not Colpitts any more."

What is a Colpitts-like xtal oscillator supposed to be called?

RE: Building a Colpitts

A crystal oscillator - I suppose?

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Building a Colpitts

You may use 'faster' transistors, like MPF102 (FET) or BF240 (NPN), etc.  Those work well even at UHF.

Regards,
Gonzalo

RE: Building a Colpitts

"A crystal oscillator - I suppose?"

Such a name fails to provide much info on the architecture. It would be like calling an oscillator an 'LC Oscillator' - perhaps accurate but unenlightening.

My ARRL handbook (1989, p. 10-1) shows four xtal oscillators in Figure 1: Pierce, Colpitts, Harmonic, and Overtone. The (xtal) Colpitts has a 10k resistor and two capacitors (47 & 100pF) in series across the xtal, and the feedback is tapped into their junction. Given the difficulty of tapping into the middle of a xtal, perhaps this explains the nomenclature discrepancy.

Cheers.

RE: Building a Colpitts

The idea of tapping into a fraction of a series resonance circuit is common to Colpitts and Hartley. Using an artificial midpoint may very well correspond to either the Colpitts or Hartley structure. Not just Colpitts.

So, which one should give name to such a circuit? Not that it matters much.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Building a Colpitts

Hiya again-

In my grandfather's old (circa 48) ARRL hand book they mention and build a VFXCO (variable frequency crystal oscillator). Using the old FT243 (????) cases (the ones with the three machine screws in them and the "thick" metal plate. Popular from WWII era stuff), they drilled and tapped a 4-40 screw in it and mounted a knob on the outside of the screw. This variable pressure changed the frequency of the crystal up to 10KHz or so.  

One could use that for finding the "sweet spot".

They also had an article on "hand lapping" the crystal to move the frequency of surplus crystals UP.  Included, if I remember correctly was to lap a slight angle on one corner of the crystal to get it to "ring" better.

  Cheers,

   Rich S.

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