[time-nuts] Interesting frequency standard project

Bob Camp kb8tq at n1k.org
Fri Jul 4 17:47:34 EDT 2014


Back a long time ago (when the rules were written) 20 Hz sounded like a pretty good stability limit on MW. The idea of anybody having a speaker that could reproduce beat notes in the 20 to 40 Hz range a likely thing. 

Fast forward many decades, and indeed people *do* have speakers that do pretty well (often more than well ….) at those frequencies. In the case where on channel interference is indeed an issue, the rational solution is to get the beat note down under 10 Hz. Still not a big deal, a 1 ppm source on both ends (good TCXO) will do the trick. 

For what ever reason (gee I wonder …) there are often only two stability options on an exciter. One is the standard stability that easily meets the FCC regs. The other is a “high stability” version that might well be Rb based. It will also take care of weird situations like needing to control placement of a 3rd order product at a co-located TV transmitter.

On Jul 4, 2014, at 5:21 PM, paul swed <paulswedb at gmail.com> wrote:

> An interesting article much like one Bert sent me circa 1989 quite recently.
> The key to these systems is that the transmitters have very good references.
> In the US at least we have no requirement for that level of stability on
> the MW broadcasts. Though evidently some stations are quite good. I think I
> have a list some place have to re-look.
> Curious can you see a schematic or must you subscribe...
> It is a nicely written article. I used to buy elctor in the book stores
> when it was available.
> Thanks
> Paul
> On Fri, Jul 4, 2014 at 8:11 AM, Collins, Graham <CollinG at navcanada.ca>
> wrote:
>> I am sure there are others on list who follow Elektor Magazine and even
>> perhaps their forums but there are likely many that do not.
>> I stumbled across this interesting frequency standard project and thought
>> others might also be interested:
>> http://www.elektor-labs.com/project/low-cost-frequency-standard-disciplined-by-france-inter.14000.html
>> A bit of light reading and nothing really new to the old hands but it
>> seems that person is well on the way to being a time / frequency nut if not
>> already there.
>> Cheers, Graham ve3gtc
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