[time-nuts] 5MHz x 10MHz

[Pete Lancashire]

Another 5 MHz HP was the 5360A


On Fri, Aug 2, 2013 at 6:14 PM, Bob Camp <lists at rtty.us> wrote:

> Hi
>
> The math is pretty simple:
>
> The Q of quartz goes up as the frequency goes down.
>
> A crystal resonator's performance (Q)  is limited by it's thickness to
> diameter ratio.
>
> At some point the resonator design impacts the Q of the resonator more
> than the Q of the raw quartz.
>
> Holders are available that will rationally hold a maximum diameter blank.
>
> It's the intersection of all of the above that implies a best solution.
> The "sweet spot" is not just quartz, it's the combination of all of the
> above.
>
> Change any of the above (like the holder) and you get another "sweet spot"
>
> -------------------------
>
> Is that simple? Of corse not. Many things need to change to let you make a
> high performance blank that's much bigger. Many things need to change to
> keep the Q of the quartz the limiting factor.
>
> -------------------------
>
> Why has it not been done? The drive in the marketplace is to smaller /
> cheaper. This is totally the opposite direction from that. The investment
> to make larger blanks goes at least back to the design of the gear that
> grows quartz. What we have is "good enough", but it's far from the best we
> could do. Quartz is not the limiting factor.
>
> Bob
>
>
>
> On Aug 2, 2013, at 7:52 PM, Tom Knox <actast at hotmail.com> wrote:
>
> >
> > Interesting, I have heard for years from the senior Time and Freq
> researchers I work with that 5MHz was a sweet spot. I will ask if there is
> a reason and proven physics behind it but these are individuals that are
> well grounded in science.  They almost always multiply 5MHz if they needed
> 10MHz etc.
> > Perhaps I missed something. It wouldn't be the first time I was schooled
> by the TimeNuts.
> > Best Wishes;
> > Thomas Knox
> >
> >
> >
> >> From: lists at rtty.us
> >> Date: Fri, 2 Aug 2013 14:39:21 -0400
> >> To: time-nuts at febo.com
> >> Subject: Re: [time-nuts] 5MHz x 10MHz
> >>
> >> Hi
> >>
> >> Quartz it's self has no "sweet spot". The only issue is how low you can
> go in a specific sized crystal holder before you start to run into trouble.
> A TO-5 crystal will have a different minimum frequency than an HC-40.
> >>
> >> Bob
> >>
> >> On Aug 2, 2013, at 2:30 PM, Mike Feher <mfeher at eozinc.com> wrote:
> >>
> >>> It was my understanding that this "sweet spot" was optimum a little
> above 3
> >>> MHz, so, 3rd overtone crystals are used to generate a stable, low phase
> >>> noise 10 MHz.  Prior to that, 5 MHz was used and before that 1 MHz
>  Regards
> >>> - Mike
> >>>
> >>> Mike B. Feher, EOZ Inc.
> >>> 89 Arnold Blvd.
> >>> Howell, NJ, 07731
> >>> 732-886-5960 office
> >>> 908-902-3831 cell
> >>>
> >>> -----Original Message-----
> >>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]
> On
> >>> Behalf Of Tom Knox
> >>> Sent: Friday, August 02, 2013 2:02 PM
> >>> To: Time-Nuts
> >>> Subject: Re: [time-nuts] 5MHz x 10MHz
> >>>
> >>> It is my understanding that Quartz has a sweet spot at 5MHz that makes
> it
> >>> ideal if the lowest possible phase noise and highest stability are
> needed.
> >>>
> >>> Thomas Knox
> >>>
> >>>
> >>>> Date: Fri, 2 Aug 2013 19:57:16 +0200
> >>>> From: magnus at rubidium.dyndns.org
> >>>> To: time-nuts at febo.com
> >>>> Subject: Re: [time-nuts] 5MHz x 10MHz
> >>>>
> >>>> Hi Euclides,
> >>>>
> >>>> On 02/08/13 18:31, Euclides Chuma wrote:
> >>>>> Hi,
> >>>>>
> >>>>> Why any equipments use 5 MHz and others use 10 MHz reference
> standard?
> >>>>
> >>>> There are some benefits (traditionally) in using 5 MHz over 10 MHz,
> >>>> but
> >>>> 10 MHz have become a common standard. The actual frequency isn't
> >>>> really magic, but 5 MHz and multiples became somewhat standard in the
> >>>> old MIL STD 188 for time-keeping, and it fit fairly well with what was
> >>>> already in use. There are folks here that can correct me on massive
> >>> details.
> >>>>
> >>>> Today 10 MHz is more common because, well, engineers then to be
> >>>> following habits, and 10 MHz "sounds nice". I use 10 MHz mainly
> >>>> because the application requires it, otherwise I use whatever
> >>>> frequency fits my other needs, or what becomes easy to source.
> >>>>
> >>>> PS. Have not seen you post before, so welcome to time-nuts!
> >>>>
> >>>> Cheers,
> >>>> Magnus
> >>>> _______________________________________________
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> >>>> and follow the instructions there.
> >>>
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> >>
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