[time-nuts] Re: Low Phase Noise 10 MHz bench signal source sought

[Joseph Gwinn]

On Sun, 03 Apr 2022 03:30:27 -0400, time-nuts-request at lists.febo.com 
wrote:
time-nuts Digest, Vol 216, Issue 4

Multiple responses interspersed below.

> 
> ------------------------------
> 
> Message: 5
> Date: Sat, 2 Apr 2022 07:13:32 -0700
> From: "Lux, Jim" <jim at luxfamily.com>
> Subject: [time-nuts] Re: Low Phase Noise 10 MHz bench signal source
> 	sought
> To: time-nuts at lists.febo.com
> Message-ID: <ef509fe2-db3c-e239-91d3-3ec0bc69c2e5 at luxfamily.com>
> Content-Type: text/plain; charset=UTF-8; format=flowed
> 
> On 4/1/22 2:12 PM, Joseph Gwinn wrote:
>> I'm looking for suggestions for AC-powered 10 MHz sinewave laboratory
>> signal sources with very low phase noise, having a noise floor below
>> -170 dBc/Hz.  Rubidium is desired, but not essential.  Reliability
>> and durability in lab use is essential.
>> 
>> Which makes and models should I consider purchasing?
>> 
>> I like the SRS model FS725, but its noise floor is too high at -150
>> dBm/Hz, 20 dB noisier than many things I may wish to measure.
>> <https://www.thinksrs.com/products/FS725.htm>
>> 
>> Thanks,
> 
> Ultimately, what you're looking for is a "oscillator and distribution 
> amp in a box with a power supply" - you can build it yourself, or you 
> can contract it out to a variety of places, or you can go to an 
> oscillator manufacturer.
> 
> Call Wenzel Associates (https://www.wenzel.com/) - they'll put some of 
> their low noise sources/distribution amps into a box with a power 
> supply. For a price. Their website is broken for these kinds of 
> products, but it's something they do all the time.

Yes.

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> 
> 
> Message: 16
> Date: Sat, 2 Apr 2022 18:13:42 -0700
> From: "Lux, Jim" <jim at luxfamily.com>
> Subject: [time-nuts] Re: Low Phase Noise 10 MHz bench signal source
> 	sought
> To: time-nuts at lists.febo.com
> Message-ID: <08b0df36-9358-8950-9c1e-54b02c04a882 at luxfamily.com>
> Content-Type: multipart/mixed;
> 	boundary="------------75rdw5reGZnT1q5be5m0JRMp"
> 
> On 4/2/22 4:47 PM, Joseph Gwinn wrote:
>> On Sat, 02 Apr 2022 03:27:06 -0400, time-nuts-request at lists.febo.com
>> wrote:
>> time-nuts Digest, Vol 216, Issue 3
>> 
>>>    11. Re: Low Phase Noise70 10 MHz bench signal source sought
>>>        (Richard (Rick) Karlquist)
>>> 
>>> Date: Fri, 1 Apr 2022 19:12:07 -0700
>>> From: "Richard (Rick) Karlquist" <richard at karlquist.com>
>>> Subject: [time-nuts] Re: Low Phase Noise70 10 MHz bench signal source
>>> 	sought
>>> To: Discussion of precise time and frequency measurement
>>> 	<time-nuts at lists.febo.com>,        Bob kb8tq <kb8tq at n1k.org>
>>> Message-ID: <0f524fb8-2220-635e-3f62-28f7f081665e at karlquist.com>
>>> Content-Type: text/plain; charset=UTF-8; format=flowed
>>> 
>>> He [Joe] should be looking at Wenzel Associates and NEL.
>>> Wenzel specs -170 dBc at 100 Hz offset.
>> I know of Wenzel, but they don't make bench-top lab instruments.
>> Rack-mount is available, but as a custom part.
> 
> Wenzel will be happy (for a price) to put it in any size or shape box 
> you want. Most people want rack mounts, but it's mostly a matter of 
> sheet metal work and they can certainly do that.

Yes.

> Depending on your frequency and performance, you *might* find a "in 
> stock"  oscillator.  A 10 MHz Onyx or something like that might be 
> basically stock.
> 
...
> 
>> 
>> What is also needed is a very quiet source of DC power for the Rb,
>> OCXO, et al.  None of the vendors seem to specify their PSRR (power
>> supply rejection ratio), and I assume that all published curves are
>> obtained using a battery-powered unit under test.
> 
> No, that's a "call them and ask", but most have pretty good PSRR 
> (although what are you looking for?) - the guy or gal on the phone will 
> tell you what it is in a "not guaranteed on the data sheet" sort of way. 
> Unless you want them to hit a spec, but you'll pay for it.

The basic requirement intent is simply to not undermine the 
performance of the OCXO being powered.


> https://wenzel.com/model/btuln/ mentions that they have an internal low 
> noise regulator - it's about 5dB shy of your -170 at 100Hz requirement.

This BTULN OCXO looks very good.  While they do mention that it 
contains its own regulator, no numbers are given, so it's hard to 
know what to make of that claim.

 
> I wouldn't assume battery power - but this is where a phone call helps - 
> they'll be happy to tell you.

I must say that I've run into the battery-power (or *really* good lab 
power supply) approach, neither which is applicable in non-lab 
applications.  I suppose if Wenzel does the packaging, they will 
ensure that full OCXO performance is achieved when powered from the 
usual lab AC power.  The box would also shield the power wiring and 
frequency-control input (if any) and associated wiring from passing 
EMI.

Joe Gwinn







> ------------------------------
> 
> Message: 17
> Date: Sat, 02 Apr 2022 18:16:50 -0700
> From: Hal Murray <halmurray at sonic.net>
> Subject: [time-nuts] Re: Low Phase Noise70 10 MHz bench signal source
> 	sought
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at lists.febo.com>
> Cc: Hal Murray <halmurray at sonic.net>
> Message-ID: <20220403011650.3C56628C17A at 107-137-68-211.lightspeed.sntc
> 	ca.sbcglobal.net>
> Content-Type: text/plain; charset=us-ascii
> 
> 
> richard at karlquist.com said:
>> The tester they used for ADEV consisted of a special 10811 that was 500 Hz
>> off frequency driving a dual mixer box (Model 10514?) which 
>> produced a 500 Hz
>> beat note, which then drove an ADEV system  (model 5490?).  Only a 
>> few of the
>> offset 10811's were produced due to the obvious disruption to the 
>> production
>> line because of the offset frequency. 
> 
> What can mortals do if they want a good reference oscillator with an offset?
> 
> Or maybe I should turn that around.  How good can I get if I want 
> an offset?  
> And how do I do that?
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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