[time-nuts] Re. DIY atomic "resonator"

Bob kb8tq kb8tq at n1k.org
Wed Apr 12 10:44:50 EDT 2017


Hi

According to the data sheet the X version of the 2400 has a TCXO in it. The “not an X” has an XO. “Setability” of the XO is <0.5 ppm and
the TCXO is rated at 0.2 ppm. Maximum resolution on the device occurs with a 20 MHz input. That gives you +/- 0.05 ppm. The 200 MHz
range is scaled by 10 and the 2.4 GHz input is scaled by 128. Neither one gives higher resolution than you get at 20 MHz. A source good
to 0.05 ppm would only degrade the device by 1 LSB. A 0.01 ppm source would be adequate to ensure the final LSB is good. Any of the 
normal eBay telecom Rb’s would likely be good enough forever and ever, even without calibration. I have yet to see one that was off by 
> 0.001 ppm. 

Bob


> On Apr 12, 2017, at 10:01 AM, Tom Van Baak <tvb at LeapSecond.com> wrote:
> 
> An update about this thread...
> 
> It turns out that OP (Andre) would like the readings of his vintage Black Star (UK) Nova 2400[X] 8-digit 2.4 GHz bench frequency counter to be accurate and stable to the 8th digit. That's all. The internal XO or TCXO is not good enough for that last digit or two. Not to mention the cal date is 1996.
> 
> So the good news is that he is *not* embarking on a life-long project to build his own atomic clock. This thread is just a newbie looking for a simple answer to an accuracy / stability / calibration question. His counter has a BNC for external timebase, so ...
> 
> I think it would help him if any UK/EU time-nuts:
> - have a 1e-9 or 1e-10 level OCXO to spare -- which he would have to calibrate, or
> - can help him locate a surplus telecom Rb -- inherently good enough that calibration is not even required, or
> - point him to a cheap newbie-friendly 10 MHz GPSDO -- if his environment would make that possible and reliable.
> 
> I would guess that a mere 8-digits of accuracy/stability should cost no more than 100 these days. If you can help, please send him email, off-list.
> 
> Again, OP is not looking for laboratory-grade accuracy or to build his own atomic clock from scratch. It's just an 8 digit counter.
> 
> /tvb
> 
> ----- Original Message ----- 
> From: "Andre" <Andre at Lanoe.net>
> To: <time-nuts at febo.com>
> Sent: Tuesday, April 11, 2017 12:31 AM
> Subject: [time-nuts] Re. DIY atomic "resonator"
> 
> 
>> Hi all.
>> 
>> As a first step, I wanted to build a specific hydrogen line (1.420 GHz) preamp.
>> 
>> Seems that some fluorescent tube starters do emit a very brief burst at around 1.4 GHz
>> 
>> during a specific portion of the initial switch-on surge when cold and actually observed this here.
>> 
>> 
>> Also relevant, this same preamp can be used for GPS and if you're living in an RF proof flat
>> 
>> with only one good radio station its hard to get any signal.
>> 
>> 
>> Has anyone else either built an atomic clock around a bare Rb lamp module "core" or attempted
>> 
>> to make a hydrogen maser?
>> 
>> It would be a fascinating project to integrate SDR as these are (with modifications) very accurate
>> 
>> and can be used to fine tune a lot of the oscillators etc with less hassle.
>> 
>> 
>> Thanks, -Andre in Guernsey
> 
> 
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