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audioguru said:It is best to test your clock circuit after it has warmed-up. Its frequency will be stable and that's the way you will use it anyway. :lol:
Screech said:It's very interesting when you put 4 quartz clocks infront of you and you watch the second hands/display for a few hours
One of them, a no-named digital was a second slow only after 40 minutes.
Another, a seiko quartz analoge, was a second slow after a few hours.
compared to my pc clock.
Don't know the battery state of the clocks.
Interesting.
I never would have thought of that.If you have Teletext in your country?, try comparing it to the Teletext time (ensure you use the same channel every time though).
You can't trust them!Nigel Goodwin said:If you have Teletext in your country?, try comparing it to the Teletext time
audioguru said:You can't trust them!Nigel Goodwin said:If you have Teletext in your country?, try comparing it to the Teletext time
When I had a VCR it set its clock automatically to "teletext?" from a TV station. Then it screwed-up. I e-mailed them and they thanked me for pointing out their problem and it took about 1 month for it to be fixed until it screwed-up again a few months later.
On my new digital recorder I just highlight the program on the cable TV's guide channel and push the Record button on my remote. It even knows if my program is delayed or runs into overtime. :lol:
Nigel Goodwin said:It doesn't sound like your TV stations are very reliable?.The station is an old non-profit American one. Canadian stations are newer and more reliable but don't broadcast the time signal.
Yeah, it's digital cable-TV. They must have a whole army of many people keying in the stuff. :lol:Or is it a digital TV system?, which again must send some kind of start and stop signals to accurately record a program - and obviously relies on these signal being inserted!.
Nigel Goodwin said:The crystal is tuned by altering the DIFFERENCE on the two sides of the crystal, so by adding to BOTH sides you're not really changing anything 8)
Not so, it is the capacitance in parallel with the crystal which changes the frequency.
If you have 27pF at each side of the crystal, you will have 13.5pF in parallel with the crystal. (The capacitors are in series and centre tapped to 0v). There will also be the stray circuit capacitance.
27 pF at each side of the crystal is not the same as 39pF at each side. In the 39pF case, the frequency will be lower.
JimB
But we can't trust radio RDS time data!Nigel Goodwin said:audioguru said:You can't trust them!Nigel Goodwin said:If you have Teletext in your country?, try comparing it to the Teletext time
You can in the UK, where it was invented! :lol:
The crystal is tuned by altering the DIFFERENCE on the two sides of the crystal, so by adding to BOTH sides you're not really changing anything 8)
Not so, it is the capacitance in parallel with the crystal which changes the frequency.
If you have 27pF at each side of the crystal, you will have 13.5pF in parallel with the crystal. (The capacitors are in series and centre tapped to 0v). There will also be the stray circuit capacitance.
27 pF at each side of the crystal is not the same as 39pF at each side. In the 39pF case, the frequency will be lower.
Screech said:My tests confirm what you say JimB, it did run slower with bigger caps on each side of the crystal. see my graphic below.
What's our teacher gonna say?
I'm wondering , maybe the caps are not not identical (5% difference on tolerence)?
JimB said:Never mind what the teacher says, he may learn something too.