[time-nuts] Thunderbolt, Rb,
Leigh L. Klotz, Jr WA5ZNU
Leigh at WA5ZNU.org
Fri May 21 01:03:25 UTC 2010
Thanks for thinking about and commenting on my project. The goal is to
show how you can use a scope in interesting ways. One of the ways is to
show that you can measure fraction PPB in stable, periodic signals, and
you don't need a $5000 LeCroy, just a stopwatch and a few minutes.
The FE5680A Rb DDS is settable to within 6mHz steps, so it's got a built
in difference with the Tbolt already and should show one cycle
difference in 1/6mHz ~= 160 seconds. I don't intend to do any demos
that involve adjusting the C Field, since I used Mark Sims' program to
calculate the closest divisor word for 10MHz already, by reading the
2^24 Hz divisor word and working backward, and I don't want to lose that
Sadly, there's not a good view of over 50% of the sky, even though I'm
able to place the antenna outside. But in my test today it was getting
more than 4 sats and the scope was taking a minute or two to go from
peak to peak, so I'm happy.
Tomorrow, the school demo will be a paper scope made out of a yard
stick, a marker, and wall-chart paper: one student holds the oscillating
yard stick, a second pulls the paper steadily, and a third times it.
Afterward, they count peaks and divide by time. Next student demo is
the scope made out of a laser and hard drive with a mirror on the voice
coil. For the real scope work, we won't show the Rb to the kids;
they'll get an iPod with music on the scope, as it's more relevant to them.
But please do stop by on Saturday or Sunday during the regular days and
say hi. I'm really pleased with all the help I've gotten from this list
and from reading its archives.
> The rubidium should tune over a +/- 1x10^-9 range. A nanosecond per second isn't all that hard to spot. At 10 MHz you'll do a full 360 in 100 seconds.
> On May 20, 2010, at 5:57 PM, WarrenS wrote:
>> I hope it is a LONG show with a lot of patent people.
>> This is way above the typical WWV stuff.
>> Any good adjusted RB with a correctly set up Tbolt will take>2.5 hrs to do the 360.
>> Delta 1e-11 = 10,000 sec for 100 ns change.
>> I understand it is not what your desired goal is,
>> But would be much better off with a PC and Lady Heather, that way only need to wait a minute or less.
>> Maybe a better test for the O-Scope is to show the noise jitter between them.
>> time-nuts] Thunderbolt, Rb, Scopes at SF Bay Maker Faire this weekendLeigh L. Klotz, Jr. WA5ZNU Leigh at WA5ZNU.org
>> Thu May 20 20:00:21 UTC 2010
>> As part of the SF Bay Area Maker Faire this weekend, I'll be showing a
>> Thunderbolt GPSDO and a FE-5680A Rubidium disciplined oscillator, both
>> connected to a $25 flea-market oscilloscope.
>> The demo is part of a hands-on "things to do with oscilloscopes." In this
>> experiment, we'll have visitors use a stopwatch to measure how long it
>> takes for a 360 degree phase change, and use that to calculate the
>> fractional PPB difference between the two frequencies.
>> We'll be at the ARRL booth, which is in the Fiesta Building, near the
>> Tesla Stage entrance.
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