References...no, not my CV...

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References...no, not my CV...

Postby Steve Anderson » Sun Apr 20, 2008 1:43 am

Perhaps the most two important measurements in electronics are Voltage and Frequency (1/time). The accuracy of which will eventually determine the go/no-go status of some project or another. This need not just apply to NBTV.

For Voltage I invested in the best grade LM4040 I could get at 5.0V, the LM4040-5.0A which is within ±0.1%. Ideal for checking your DVM on a monthly basis.

As for time/frequency, I went for broke. The GPS system. This is so accurate...forget it. 10<sup>-11</sup> is common, nay daily.

A chap in the UK sells 'sort of' DIY versions that provide the basis, the rest is up to you.

http://www.jrmiller.demon.co.uk/project ... frqstd.htm

I attatch how I interfaced James' GPSDO to my world, he has a newer version, but it should be very similar. I added a power-outage indicator as we have many here, a voltmeter to keep an eye on the PPL status, and an oven temperature indicator.

Also attatched is the view of the sky that the GPS receiver gets here over a 24hr period.

Steve A.
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Postby Viewmaster » Mon Apr 21, 2008 12:13 am

I had a look at that.....£250 to get within .05Hz at 10GHz !!
I am wondering when one would need such performance for NBTV ?

So, pardon my great ignorance, Steve, but why spend £250 for this great accuracy? What will you use it for I wonder?
Albert.
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Are you clocking my bird?

Postby Steve Anderson » Mon Apr 21, 2008 12:42 am

Viewmaster wrote:I am wondering when one would need such performance for NBTV? Albert.


Maybe not for NBTV, quite correct, but there's not much worse than publishing without a half-way decent reference. If you're 'slipping' one line in 32 for some reason that requires a precision of around 3%, easy. But one pixel in 96,000...err, I like a good reference.

Even without the NBTV aspect, there are reasons to be precise when it comes to optical communications. Years ago, before GPS, we used to use the local TV stations PAL subcarrier as a reference, held by law to 1Hz in 4.43(whatever, whatever)MHz over a 24hr period.

The down side is you never have an excuse to be late again!

Steve A.

Heck, I've just given the game away by mentioning 96,000 pixels....I dare not mention 192,000 pixels....oops, darn I have...
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Re: Are you clocking my bird?

Postby Viewmaster » Mon Apr 21, 2008 4:24 am

Steve Anderson wrote:Heck, I've just given the game away by mentioning 96,000 pixels....I dare not mention 192,000 pixels....oops, darn I have...


192k pixels?. Mmmm. You must be building 125 NBTV televisors. :wink:
Where are you going to store 'em? :lol:
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Re: Are you clocking my bird?

Postby Steve Anderson » Mon Apr 21, 2008 1:15 pm

Viewmaster wrote:192k pixels?.....Where are you going to store 'em? :lol: Albert.


That is (seriously) becoming a large headache and is actually more of a challenge than the display. I have considered live sources, say a 625 camcorder output standards converted to (insert whatever format I eventually choose here).

Or even a webcam. (Cringe).

I have considered a VCR as it has the bandwidth and is uncompressed, but can I buy one here? No. Some specialist outlets in Europe might still stock them, but not here.

More anon, for sure.

Steve A.
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Re: Are you clocking my bird?

Postby Viewmaster » Mon Apr 21, 2008 6:29 pm

Steve Anderson wrote:I have considered a VCR as it has the bandwidth and is uncompressed, but can I buy one here? No. Some specialist outlets in Europe might still stock them, but not here.

Steve A.


Dozens for sale still on eBay. Not only DVD/VCR combos but stand alone VCR's too.
Postage to your place should not be too urksome.
Try searching for 'VCR' under "Consumer electronics." (worldwide)
I bought a Sony last year on eBay...it's still OK.
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