Re: [time-nuts] Temperature controlled TCVCXO

On Fri, 13 May 2016 11:38:06 -0500, you wrote: >David wrote: >> I was thinking of holding the temperature right at 25C or maybe a >> little higher at an inflection point to minimize the possibility of >> condensation. The difficulty is that the ambient temperature could >> vary above or below

Re: [time-nuts] Temperature controlled TCVCXO

Hi The first hit on Google for AT cut curves is: http://www.aextal.com/tutorial-frequency-stability.htm One common way to make a TCXO is to start with a minimum error cut over the intended temperature range. If that is -30 to +70C, you do get turns in the curve. There are several other ways

Re: [time-nuts] Temperature controlled TCVCXO

Hi Different compensation approaches call for different crystal angles. Most (but not all) TCXO’s use AT cut crystals. What varies is the angle of cut and thus the turnover temperatures. If you are buying in sufficient volume, the price of a simple OCXO is well below $10. You need to be in

Re: [time-nuts] Temperature controlled TCVCXO

Hi Nathan, Let me state what Bob is driving at in a different way. Your biggest problem with a TCXO is the crystal. It is cut so that the slope, relative to temperature, has the shallowest curve around room temperature (between 20 to 25 degrees C). If you cool or heat it from that range

Re: [time-nuts] Temperature controlled TCVCXO

Thanks for those. I went over them pretty carefully and what I am proposing is not covered by either although that would not protect me from a debilitating patent lawsuit. It does seem like the kind of thing Symmetricom would try so I am inclined to believe based on Bob Camp's reply that they

Re: [time-nuts] Temperature controlled TCVCXO

Hi Ok, with a TCXO you have a temperature sensor that tries to servo the crystal on to frequency. You also have a crystal with a temperature dependance. As you try to heat / cool the TCXO your thermal variation hits one before it hits the other. The net effect is that the ADEV is actually

Re: [time-nuts] Microchip PIC CTMU

Only found info about PICTIC 1 and 2: http://www.ko4bb.com/doku2015/doku.php?id=precision_timing:pictic Where´s info about PICTIC III? Daniel Em 13/05/2016 14:51, Attila Kinali escreveu: On Fri, 13 May 2016 07:36:10 -0400 Bob Camp wrote: Given that a “real” TDC is a

[time-nuts] GENIUS by Stephen Hawking (PBS TV), with 5071A cesium clocks

Fellow time nuts, Here in the US, a new six-part TV series on National Geographic / PBS starts next Wednesday, May 18th, 2016. The title is "Genius by Stephen Hawking" and episode 1 is: Can We Time Travel? Having not seen it yet, I can't make a promise of its "SNR" (Science to Nonsense

Re: [time-nuts] Microchip PIC CTMU

On Fri, 13 May 2016 07:36:10 -0400 Bob Camp wrote: > Given that a “real” TDC is a resistor and capacitor attached to a FPGA pin > (plus the ADC) > the cost of doing it better is not all that much. You can get down to a few > hundred ps without > a lot of crazy effort ( still

Re: [time-nuts] Temperature controlled TCVCXO

David wrote: I was thinking of holding the temperature right at 25C or maybe a little higher at an inflection point to minimize the possibility of condensation. The difficulty is that the ambient temperature could vary above or below that so the TEC has to both heat and cool but that is a

Re: [time-nuts] Temperature controlled TCVCXO

https://www.google.com/patents/US6166608 "Thermo-electric cooled oven controlled crystal oscillator " http://www.google.com/patents/US8653897 "Devices, systems, and methods for controlling the temperature of resonant elements " On Fri, May 13, 2016 at 4:15 AM, David

Re: [time-nuts] Temperature controlled TCVCXO

I was thinking of holding the temperature right at 25C or maybe a little higher at an inflection point to minimize the possibility of condensation. The difficulty is that the ambient temperature could vary above or below that so the TEC has to both heat and cool but that is a solved problem. On

Re: [time-nuts] Microchip PIC CTMU

Based on my earlier experiences with pattern dependant jitter caused by interaction between different logic circuits, a few hundred picoseconds is about what I would expect if an FPGA (or microcontroller) is controlling the charge cycle timing. I would be surprised if the PIC CTMU cannot achieve

Re: [time-nuts] Temperature controlled TCVCXO

Is the performance limited by other than temperature induced drift of the TCVCXO like the properties of the AT cut itself? It would seem odd if holding the temperature of the TCVCXO to a very narrow band did not significantly improve drift. Before the advent of better than OP-07 type low drift

Re: [time-nuts] Temperature controlled TCVCXO

A problem I had with TE heater coolers was condensation when the ambient temperature was higher than the TE temperature. I was trying to operate the crystals on the lower temperature inflection point. After a while, corrosion became a major issue. John WA4WDL Bob Camp

Re: [time-nuts] Temperature controlled TCVCXO

Can you elaborate just a little bit on "poor"? Is that due to the "flat points" or desired temps always being elevated above most sane ambient temps? Or just that temp control via TEC isn't as precise? Nathan KK4REY Sent using CloudMagic Email

Re: [time-nuts] Temperature controlled TCVCXO

Hi Yes, it can be done. The performance will be poor, but it will work. Bob > On May 13, 2016, at 4:15 AM, David wrote: > > Has anybody tried using a thermoelectric cooler to maintain a TCVCXO > at a constant temperature in lieu of using an OCXO? > > I was thinking

Re: [time-nuts] Microchip PIC CTMU

Hi Given that a “real” TDC is a resistor and capacitor attached to a FPGA pin (plus the ADC) the cost of doing it better is not all that much. You can get down to a few hundred ps without a lot of crazy effort ( still using the MCU ADC). Bob > On May 13, 2016, at 3:51 AM, David

[time-nuts] Temperature controlled TCVCXO

Has anybody tried using a thermoelectric cooler to maintain a TCVCXO at a constant temperature in lieu of using an OCXO? I was thinking about this after reading some application notes in connection with constant temperature control using TECs with bipolar drive. The power required would be

Re: [time-nuts] Microchip PIC CTMU

It is always an extra challenge to get even datasheet performance out of sampling converters which are integrated with a microcontroller and of course Microchip says nothing about noise or complete AC performance. I suspect adding an external ADC to the Microchip CTMU while possible would be a

Re: [time-nuts] Intro and Driver Request

On Thu, May 12, 2016 at 8:34 PM, John Allen wrote: > FWIW, The Win 2000 driver will work on Win XP. Digging into the SDK disk, I see there are Windows drivers there as well as source code. I was thinking they were on another disk. I'd still like to find that DOS