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Author Topic: which type of crystal  (Read 11184 times)

Offline ff

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Re: which type of crystal
« Reply #15 on: June 12, 2014, 1413 UTC »
Quote from: OMCS on June 11, 2014, 1718 UTC
These guys have been around for years.
http://jancrystals.com/

Yes, along with International Crystal and a few others who are still chugging along.  Unfortunately, nowadays the cost for a custom-cut crystal is quite out of reach for many.  Also, the manufacturers stopped producing FT243 size rocks over 20 years ago.  Many no longer mess with HC6s.  HC18s and similar are generally the largest physical rocks one can custom order nowadays.  Hamfests, Ebay sellers, and online vendors selling used rocks are the only places one can find the big fellas now.  Small rocks are fine for low power oscillators but for MOPA-type transmitters (which are usually beginner-type projects), the little chunks will overheat and fail.  I still jump on FT243s in my frequency ballpark when I occasionally come across them.  There's always some like-minded folks in need...  ;)
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Offline redhat

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Re: which type of crystal
« Reply #16 on: June 12, 2014, 1449 UTC »
Last I checked, ICM only wants about $25 shipped for a standard HC-6 crystal.  Doesn't sound that out of reach to me.

+-RH
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Offline ff

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Re: which type of crystal
« Reply #17 on: June 12, 2014, 1924 UTC »
Quote from: redhat on June 12, 2014, 1449 UTC
Last I checked, ICM only wants about $25 shipped for a standard HC-6 crystal.  Doesn't sound that out of reach to me.

+-RH

Nor to me either.  Admittedly Redhat I haven't actually purchased a custom-cut rock since the 90s.  A few years back one of my buds had a quote from Jan for an HC-6U of about $40 shipped with a lower per rock price for multiple xtals of the same freq and specs.  Buying one wouldn't hurt too much but ordering for several freqs might smart a bit, especially for some of the newbs...
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Offline redhat

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Re: which type of crystal
« Reply #18 on: June 13, 2014, 0743 UTC »
Honestly, if your going to go the multi-frequency route, a better way would be to build a simple frequency synthesizer based around a 74HCT4046 for about the same money in parts, and can generate frequencies up to 17 MHz.  That's the way I'd go :)

+-RH
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Offline ff

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Re: which type of crystal
« Reply #19 on: June 13, 2014, 1548 UTC »
Yes, I'd say the PLL is a good way to go for anyone who wants to invest the effort.  Its funny you mention the 4046 Redhat.  I'm toying with one right now, along with a 74hc74 flipflop to use as an xtal doubler.  Have you ever played with one?  I'd appreciate your thoughts... 
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Offline redhat

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Re: which type of crystal
« Reply #20 on: June 13, 2014, 2322 UTC »
The last time I built something with one was several years ago.  I build a device that had a 3 MHz oscillator in it, and divided it down to 300 Hz.  That was compared to a pulse generator on the gear train of a machine that at the proper speed would also provide 300 Hz.  The error voltage produced by the phase comparator was filtered and fed to a VFD to keep the machine at the right speed.  It took some design and breadboarding time, but its still working :)

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Offline OMCS

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Re: which type of crystal
« Reply #21 on: June 15, 2014, 1323 UTC »
I agree that some kind of vfo is the way to go, however, if you come across an old rig with the crystal plugs it's much easier sometimes to just buy one and pop it in. Used to work for a guy in the 90's who had a box full of the old style crystals, (brown bakelite square thingys) mostly ham bands but he also had some bizarre frequencies in there as well. Wish I had bought the lot off of him.
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