Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

Hi The original question related to crystals that ran down into the 10’s of KHz range. For those, a high resistance is not unreasonable at all. For more “normal” AT cut resonators in “big" packages it is not unreasonable to expect the resistance on the fundamental to be approximately the same

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

Bob - Crystal resistance of 100K probably applies to the large low frequency crystals. Modern HF fundamental crystals tend to be around 50 ohms at their fundamental and I think higher for overtone crystals. Older crystals in the HF range in the FT-247 holders seem to usually be several hundred

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

In the July/August 2008 QEX magazine there is an article by VE5FP "Some Thoughts On Crystal Parameter Measurement" that may be of interest. On Sat, Jun 4, 2016 at 11:01 PM, Bob Camp wrote: > Hi > > There are two things you may be talking about: > > 1) The pressure springs on

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

Hi There are two things you may be talking about: 1) The pressure springs on things like FT-243 holders, they are generic springs. 2) The connection leads on plated blanks, they are indeed strange *and* soldering to the blank is a big problem. I’m guessing you are in bucket number 2. Bob

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

Hi George: A Crystal Activity Meter is the most straight forward way: http://www.prc68.com/I/Xam.html -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html The lesser of evils is still evil. Original Message Hi, I have a number

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

Mike, XTALs does work in air, or better: dry gases (i.e. nitrogen) too, but OK; quality exemplares are (for better, spurious free, oscillating) in vacuum... Karl Virenfrei. www.avast.com

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

Tim wrote: The Pierce logic-gate-biased-active oscillator is pretty reliable to start and will oscillate somewhere with most crystals from kHz to MHz. As you found out, it will often come up on one of many overtones. To reduce chance of coming at an overtone, a series resistor from logic gate

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

Thanks all for your advice, hints, tips and links. Lots to read , do and some hardware to check. I don’t have a frequency generator so I’ll have to go another route. Oh. One last Q. Has anyone tried repairing the « spring » wire electric connections on large quartz plates. In one large unit

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

Tim Shoppa wrote: >The Pierce logic-gate-biased-active oscillator is pretty reliable to start and >will oscillate somewhere with most crystals from kHz to MHz. >As you found out, it will often come up on one of many overtones. >To reduce chance of coming at an overtone, a series resistor from

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

With random old crystals in holders, it often helps to disassemble the holder and clean crystal and holder plates with alcohol (my favorite back in my youth was carbon tetracholoride but not so easy to find these days.) I'm guessing most of your round blanks were for FT-243 type holders. The

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

Hi Simple approach is to assume that you have a crystal resistance in the range of 100K ohms. If you guess to high, the oscillator will just work to well :) Multiple JFETS in cascade for the higher frequency stuff should work. For anything below 20 KHz, an op-amp is likely your best bet. A

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

A vector voltmeter can be replaced by a spectrum analyser or even a 14 bit scope with or without a preamp. In lieu of phase information one can measure the 3dB bandwidth to elicit the Q, combined with measurement of the low frequency shunt capacitance and the attenuation at resonance, the

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

Some idea of the crystal equivalent circuit at the oscillation frequency would help considerably. Usually lower frequency crystals have a considerably higher series resistance than those operated at 1MHz or above. At frequencies below 100kHz or so a Meacham bridge using something likke a

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

On reflection, building a jig to measure the crystal transmission as a function of frequency may be much easier than attempting to build an oscillator for an unknown crystal. However a suitable signal generator and detector are required. Once the crystal parameters are known its much easier to

Re: [time-nuts] How to get unknown frequency quartz crystals oscillating

On Sat, 4 Jun 2016 10:46:40 +0200 Mike Cook wrote: > If you had a crystal with unknown frequency and drive requirements > that you wanted to investigate. How would you go about it? I would use some signal generator to generate a tunable sinusoid and feed this to the quartz