Hi Euclides,

On 02/08/13 18:31, Euclides Chuma wrote:

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

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

Many important lab references over past 50, 60 years are named and
characterized at http://www.ieee-uffc.org/main/history-norton.asp

2.5MHz and 5 MHz seem common as far back as the 1950's and 1960's (and I've
used some of them! e.g. Sulzer) and continue through today.

Late 60's and early 70's HP benchtop counters used a 1 MHz crystal. e.g. HP
5321B.

By the mid-70's HP Frequency counters were using 10MHz references. e.g. Hp
5383A (which for many of us was the defacto bench counter forever) most
often in a TCXO can.

Tim.

On Fri, Aug 2, 2013 at 12:31 PM, Euclides Chuma euclides@w2c.com.br wrote:

Hi

If you go back far enough, you will find 1 MHz and 100 KHz used as reference standards. They certainly were common place in gear through the 1960's.

Pre-WWII,  open 100 Kc quartz bars were often the "standard" of choice. Anything much higher than that was increasingly less stable.

Post WWII,  well behaved 1  Mc  fundamentals came along in glass sealed enclosures. Sealing them up helped a lot with aging. By the late 40's and early 50's low frequency overtone designs (1 to 5 MHz) were worked out.

5 MHz third overtones (and 5th's) became popular with the Bell Labs / Western Electric / AT&T crowd by the mid 1950's. They made and bought enough of them to turn them into a standard by the early 1960's. As cold weld packages took over from glass, the older 2.5 and 1 MHz 3rd's / 5th's became impractical.

10 MHz is a creation mainly of HP. They were more after the microwave end of the business than some of the others. The higher starting frequency gave them better phase noise and fewer spur issues.

Depending on where you are in the world, 10 MHz may or may not have caught on. The Russians stuck with 5 MHz long after HP had converted the US over to 10.

Intrinsically quartz just keeps getting better as you go down in frequency. There is nothing magic about any one frequency. Lower is always better in terms of Q, provided you can scale up all the dimensions. A 1 MHz OCXO that is 10X the outer dimensions of an 10 MHz OCXO obviously would have some limitations that had noting to do with quartz. As an example, the blank in a 5MHz precision crystal is probably 0.5" diameter. To make an equivalent 1 MHz crystal, the blank would need to be 2.5" in diameter. At 100 KHz you would have a plate 25" in diameter. Good luck finding the raw quartz for those blanks ….

Bob

On Aug 2, 2013, at 12:31 PM, Euclides Chuma euclides@w2c.com.br 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@febo.com [mailto:time-nuts-bounces@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

details.

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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@eozinc.com wrote:

Hi

It may well have been teamed up with a piece of Russian designed equipment.

Bob

On Aug 2, 2013, at 2:40 PM, Euclides Chuma euclides@w2c.com.br wrote: