David,

Besides the Symmetricom SA22c unit which can be found here :

http://www.symmetricom.com/products/frequency-references/rubidium-frequency-standard/SA22c/

There is also the Frequency Electronics Inc. unit FE-5650 which is very much the
same size and can be found here :

http://www.frequencyelectronics.com/rb_oscillators.html

The SA22c is .91" high by 3.0x wide and 4.4x long.  In contrast the FEI unit is
1.4" high by 3.03" square.  So take your pick !

The SA22c has additional options that the FEI does not have like external 1pps
sync input for connection to a GPS and RS232 communication port for enhanced data
between the SA22c and your computer.

I guess it depends upon what you need it for.

Bill....WB6BNQ

"Dr. David Kirkby" wrote:

On 05/23/11 09:31 AM, Rob Kimberley wrote:

Thank you. I don't have know what board area I have available, but I think think
its going to be considerably less than that size. I think the only option will
be to use an TCXO, which to be honest is good enough, but if there were small
rubidiums, I would consider using one. But it seems they are not as small as I
would have liked.

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?

I believe thats because RB and CS have cavities that essentially establish
the operating size, because they work at a given frequency. You have to go
to a different technology method to reduce its size, like the new
Symmetricom CS oscillator. Still overall pretty darned amazing in size and
power consumption. (Still waiting for the time-nuts offer of $100 each.
Limited time offer call before midnight. Shipping and handling included)
So at this time it would not be possible to equal the size or power of a
typical TCXO these days. 1/4 dip stuff.
Though we have given you answers you had not ever really stated what you
needed to accomplish.
Regards
Paul
WB8TSL

On Mon, May 23, 2011 at 9:07 AM, Dr. David Kirkby
david.kirkby@onetel.netwrote:

I couldn't resist commenting about how top posting annoys you.
Interestingly, I have always top posted ever since my first email way, way
back. Everyone else I dealt with in business did it that way. It wasn't
until I got involved with groups like this, that it apparently became a
problem.

It always seemed logical to me to have the answers to a question at the top
i.e. the most recent comment in the chain.

No doubt I'll get a lot of replies both top and bottom about this...
:-)
RK

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Dr. David Kirkby
Sent: 23 May 2011 2:07 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] smallest rubidium

On 05/23/11 09:31 AM, Rob Kimberley wrote:

Thank you. I don't have know what board area I have available, but I think
think its going to be considerably less than that size. I think the only
option will be to use an TCXO, which to be honest is good enough, but if
there were small rubidiums, I would consider using one. But it seems they
are not as small as I would have liked.

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?

time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

On 5/23/11 6:07 AM, Dr. David Kirkby wrote:

Depending on your actual needs/other stuff available in your device, a
non-TCXO and a temperature sensor might do as well. The non-TC means
that the crystal can be higher Q, so better close in phase noise, the
temperature sensor means you can calibrate the variation with
temperature (assuming your downstream application can work with
"knowledge" of the frequency.. if you're trying to generate 10 MHz, then
that doesn't help as much)

On 05/23/11 02:20 PM, paul swed wrote:

That makes sense
You have to go

I've bought an amateur radio transceiver - Kenwood TS-940S. This has a 20 MHz
crystal osciallator (not 10 as I stated before), but it was optionally available
with a 20 MHz TCXO, called SO-1 which sat on a small (how small?) circuit board.
But these TCXO's seem to be like rocking horse dung, so I wondered about putting
my own TCXO on a board. Then the idea of perhaps using a rubidium hit me.

Some enterprising sole is selling on eBay a circuit board which replaces the
SO-1, and has a 10 MHz reference input. But of course that means you need to
rely on having the external reference. Having it built in would be nice, but I
don't think there's enough room.

Perhaps an OCXO might be practical - better than a TCXO, but not as big as a
rubidium.

Dave

Rob,

I agree with you 100%, Top forever.

Had
K7MLR

At 06:29 AM 5/23/2011, you wrote:

A fine is a tax for doing wrong.  A tax is a fine for doing well.

Peter Cooper, of Fermi Lab, says, "Every experimentalist knows
that the apparatus, or at least your understanding of it, is
always at fault until demonstrated otherwise." He also says,
"Nature is really unmoved by what I, or anyone else, believes."

With my old Eudora, I can see top postings and not bottom ones. Unless I hit the details button and then I have to mine through the headers. Unless the poster deletes the unwanted posts text below.

At 23-05-2011, you wrote:

..Snip..

--
Raj, VU2ZAP
Bangalore, India.

I also top post...

Consider the Symmetricom model X72 Rb. I can fit 2 each in my shirt pocket.
Some variants are programmable and spec'd for 12 VDC operation.

I did have problems with one unit that had microphonics when used
with a DEMI/N5AC microwave LO synthesizer in a DEMI 10 GHz transverter.

For a 20 MHz reference used in a HF transceiver I would consider a ISO
Temp TC/VCXO at 10 MHz
and double it with suitable filtering. Provide a pot to easily "net" it
as well
as a additional 10/20 MHz output to feed the counter.
The ISOTemps have been going for 30-50$, so it is a cost effective
solution and
it may be stable enough for any HF operation. If used with a transverter,
you will still have to fight that LO drift. Unless it is synchronized
with the 10/20 MHz reference.

Stan, W1LE    Cape Cod    FN41sr

On 5/23/2011 11:36 AM, Mike Feher wrote:

On 05/23/2011 03:07 PM, Dr. David Kirkby wrote:

What board size do you have, what stability do you really need?

Can you fit a DIP14 package?

Cheers,
Magnus

Hi

If you have the power for a rubidium, there are some pretty small OCXO's out
there these days. The little guys will easily beat out a TCXO, but not their
larger OCXO cousins. For small size, indeed a TCXO is going to be your
choice, until it gets to big and you go to an XO.

Bob

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Dr. David Kirkby
Sent: Monday, May 23, 2011 9:07 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] smallest rubidium

On 05/23/11 09:31 AM, Rob Kimberley wrote:

http://www.symmetricom.com/media/files/downloads/product-datasheets/DS_SA.22

Thank you. I don't have know what board area I have available, but I think
think
its going to be considerably less than that size. I think the only option
will
be to use an TCXO, which to be honest is good enough, but if there were
small
rubidiums, I would consider using one. But it seems they are not as small as
I
would have liked.

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

David,

You should have said so in the first place.  Unless you are sure that the reference
oscillator is the base for all the generated frequencies, it would not make sense to
install a Rb source in the radio.  You are correct concerning most of the
"so-called" higher stability options in that they are barely worth the price asked
for them and only meet specs in a tightly controlled environment.

As for the size, you would be better served using a high quality miniature oven
controlled crystal oscillator (OCXO).  A number of companies produce such items,
with some having extremely good specs.  If you do go that route, select one that has
an electronic frequency control (EFC) port so you can have the option of external
control if you want it.  You would have to design and build your own phase locking
circuit unless some company's oscillator offers that.

However, do not expect that having a PERFECT reference oscillator precisely on 10 or
20 MHz will put you perfectly on frequency as you will be disappointed.  In a fully
DDS generated (all signals from a or multiple DDS's) radio scheme they only come
"CLOSE."  You will never ever get "right" on because of the binary nature and
resolution of the DDS.  Especially with the older radios as the DDS resolution was
lower than can be had these days.

So it is a question of "What is good enough" for the intended product.  In the
Amateur radio world One hertz is considered the best basic step size.  Many radios
only displayed and used 10 hertz step size which can be easily had with a 28 bit DDS
(a 0.1xx hertz error).  Many of the most modern radios are only using a 32 bit DDS
which translates into a 0.01xx hertz error.

By the way, the error factor of the DDS is not consistent, again due to its binary
nature.  If you utilize the Analog Devices web site ADIsimDDS app you will see that
the error offset is all over the map.  The best that can be done is to make sure the
error factor is outside the measurement frame by decade or more.

Keep in mind that the clock frequency for the DDS determines the number of sampling
points for the constructed signal.  So as you climb higher in the frequency in
relation to the clock of the DDS, the number of sampling points go down.  Here is
the URL for the Analog Devices simulator :

http://designtools.analog.com/dtDDSWeb/dtDDSMain.asp

73....Bill....WB6BNQ

"Dr. David Kirkby" wrote:

On 05/23/11 06:17 PM, Magnus Danielson wrote:

I don't actually know, as I don't have the transceiver yet. But given the board
sold had basically a TCXO and not much else on it, its not going to be large
enough for a rubidium.

To be honest, a bog-standard crystal is probably just about good enough. There's
not much point in going much more accurate. But an TCXO was offered as an
option. Getting that would be a "nice" improvement, but they are hard to get. I
suspect they would fetch as much as a rubidium due to their rarity.

But if I'm going to design my own board and put on an osciallator, I might as
well put a small ovened oscillator. Most of the hassle will be designing the
circuit - the cost of the device is not going to be a major hassle.

Give theres a wide range of volatages in the rig (including 28 V for the final
PA transistors), fitting a small over should not present any big problems.

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?