Hey ya'll... I was wondering if it was possible to combine crystal oscillators to produce a great clock speed? IE... if I combine a 10MHZ crystal with a 20MHZ crystal, could I get a combined output of 30MHZ? Or is this not possible? Thanks.
Lyos Gemini Norezel

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If you could get the crystals' frequencies of overtones and harmonics to coincide closely enough you might be able to do some oddball thing like that, but I can't imagine any practicality to it. Crystals are cut in different orientations relative to the lattice structure of the quartz with the intention of vibrating in a particular mode and at a particular frequency the designer had in mind. They are essentially resonant circuits with an extremely high Q. When frequencies are added or subtracted in analog circuits for radio use, the signals go through an analog multiplier. This is commonly called a mixer, although that term is quite inaccurate. The mixer's output consists of the two input frequencies, plus the sum of the two, plus the difference between the two. It is followed by a filter that selects the product you want and rejects the others. For digital applications, it's not normally worth the complexity.

Something else you could do with a digital crystal oscillator would be to have your logic clock output directly feed one input of an XOR gate, but also take that signal and use an RC followed by a Schmitt trigger in order to feed the other XOR input with the same square wave signal 90º behind. That way the XOR gate's output will be twice the input frequency. It's probably all academic though. For fewer parts and reduced complexity, just get a higher-frequency oscillator. Crystal oscillators do go way beyond the 30MHz you mention.

I know that crystals go way beyond 30 MHz but I was just using that as an example... what I actually want is a frequency of 1THz (terrahertz). To date NO ONE has made a crystal that works at that frequency. I was hoping to use a bunch of the 5.8GHz crystals together to equal the frequency I want.
Lyos Gemini Norezel
BTW... I know this cannot possibly apply to the 6502 itself... but a periferal (sp?) device I am developing can.

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For 5.8GHz, I'm sure the crystal is used to first derive a much, much lower frequency which gets multiplied to get the 5.8GHz.

I worked in UHF power amplifier design in the mid-1980's, mosly for military applications. Without writing a small book here, I can suggest that you get some education in the field, find an employer that'll give you some experience, and set up a budget of about a quarter million dollars for test equipment. Actually a good first smaller step would be to pass the tests for an amateur radio license. 1THz is not just CB radio at 35,000 times the frequency.

Garth
WB6NUY

As far as I understand, you will never be able to achieve a clock rate of 1THz. This is essentially very deep infrared/extremely energetic microwave. To generate these kinds of frequencies, your best bet is MASER -- microwave amplification through stimulated emission of radiation. It's basically the use of a tuned cavity resonator that is essentially fed white-noise. The resonator filters out the 1THz signal, and may be able to use the excess energy from the white noise to amplify it.

Then, to convey it to another device, you need a pipe. Literally. The pipe's diameter would be, by my calculations, close to 0.3mm in diameter. It's going to be hard to bend the tube and not distort it, thus causing signal attenuation.

In sort, I have to wonder, why in the world are you considering 1THz?

I'm certainly no expert, but I think the tuned cavity just makes it regenerative
and maybe an oscillator, it's not necessary for "masing"




Way back in the before times they used a spark gap and a tuned circuit
to generate RF.

I wonder if you coupled a tuned cavity to a spark gap, or maybe an avalanche
diode, you could get useful terahertz

Or maybe s/he could find a couple of infared diodes to beat against each other
(don't ask me how )



I'm curious about that my self.

Because the terrahertz zone is entirely unused. Even the government can't use the terrahertz zone yet. Therefore, as far as communications goes, it's the most secure. Ie., no one on the band... no possible snoopers.
Lyos Gemini Norezel

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> Because the terrahertz zone is entirely unused.

Uh, there happens to be a reason for that, just like there's a reason no one has made an airliner that can get you from Los Angeles to Paris in 20 minutes. It doesn't mean you can easily jump into a market no one has thought of and make a killing.

Regardless of technology though, I doubt that a THz signal would make it through a damp piece of paper. You can't use any wire or even transmission lines at those frequencies either, and as Samuel pointed out, even waveguides would be highly impractical.

There are plenty of other neat things to explore for communication, like lasers, encoding your data to defend against snoopers, or using any of the many GHz amateur radio bands. The latter will require a big test equipment investment too, unless you can find some off-the-shelf plug-n-play products.

Lynx makes tiny UHF transmitters, receivers, and antennas you can use for data without a license. You can get a whole set from Digi-Key for under $100, and it will almost be plug-n-play. Range is typically a few hundred feet. I made a provision to plug one of these transmitters and/or receivers into my workbench computer, but haven't actually used them yet, so here they sit, collecting dust.

You're not supposed to put digital data on CB radio, but at this point I'm not sure anyone would care anymore. It seems to be treated like the garbage pile of the radio spectrum.

Amateur radio opens up all kinds of doors (besides the ones people usually associate with amateur radio), including your own television transmission (not on commercial TV frequencies though), making your own radar, telemetry, fax, digital communications, VLF, using amateur satelites for repeaters, etc. etc..

This is not as absurd as you might think it is. I haven't been in the field of photonics for some time, but I distinctly remember that there are crystals that one can grow that effectively modulates "OF" (optical frequency, my own term) against an electrical AF/RF signal, to produce a new OF. I believe the process is reversible as well.

Therefore, I do believe that one may be able to exploit the properties of such optical crystals to produce a precise, and even calibrated, 1.0THz signal.

OK, I know that this is still "close enough" to 1THz, but my FCC rulebook states that anything above 300GHz is equally "free for all" too. Heck, even as high as 100GHz, RF emissions are *so* directional that using a directional antenna that even has something like 5 elements is just as if you're using a flashlight.

I used to be into microwave communications as part of my ham radio hobby. I may get back into it someday. We'll see. Right now, I don't think I've fully exhausted everything I could do on HF or VHF yet.

Only if you want an oscillator and not always then (google "phase conjugating mirror")

What kind of crystals would this entail using? Where can I get ahold of such crystals? Can you give me any electrical, PCB style, descriptions of how I could use this in AF/RF transmissions? Can you explain how to "calibrate" these crystals?

I have no intention of "making a killing". This is gonna be for private use only. This'll be for me and a few select friends to use as almost instantaneous communication.

What do you mean by this?
Thanks Ya'll
Lyos Gemini Norezel

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I mean how would I wire these crystals? I've never dealt with the crystals themselves... though I have used oscillators and prewired clock crystals.
Lyos Gemini Norezel

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Mundus Vult Decipi et Decipiatur

No, no, no, no, and no, in that order.

You don't wire them up -- these work entirely on the E-fields of illumination from coherent light sources -- e.g., you shine modulated light beams into them, and interacting lasers produce the modulation desired.

These crystals are grown and constructed on an individual basis, as-needed. As far as I am aware, they were not available commercially, since they were still R&D material. However, I have seen several telco-grade optical TDM switches for OC-192 that employs these kinds of modulators. Perhaps google for dense wavelength modulation? I'm not too sure how else to find them.

Anyway, since this is all beyond my field of expertise (I was 16 when I worked for Rome Labs in the Photonics division, which would put the date at around 1991, and as an intern at that), I don't have any further answers for you. Sorry.

Hi, maybe not the best topic to ask, and maybe not the right forum ... It seems I have lack of knowledge about quartz crystals. I'm wondering if someone can help, or suggest me some on-line resources about this topic. The problem when a schematic states that I need a quartz for 12MHz. But electronic shops often has different types for a single frequency like "HC49U" and "HC49S". One of them all taller, but I am not sure if there is other difference. Also, some description about a given schematic states that I need parallel (or serial) cut crystal ... But still if I go (I tried ...) into an electronic part shop here in Hungary and I try to ask for "parallel cut crystal for X Mhz" then I was gazed with eyes saying something like "what the hell he is wanting ... it's X MHz, what is that parallel/serial stuff?". Or the "S" in "HC49S" means serial maybe? Reading the price list of my usual shop indicates that they usually have HC49U and HC49S for each available frequencies. The problem is even more serious for me, when the schematic (or its description of course) does not specify if I need serial or parallel cut.

Hopefully I haven't asked too stupid question, but I really have no idea about these ...