[time-nuts] GPS and Rubidium frequency standards and noise question (new...

Said Jackson saidjack at aol.com
Sun Jun 3 19:33:03 UTC 2012


hello Rex,

from what I have seen the lowest noise is available on the Z3801 with 10811. I also have a Z3815 with E1938A oscillator, but the 3801 is much less noisy and more stable. Don't have a 3816 or 3805 to test against.

Keep in mind that there is  a large performance variation from unit to unit as can be seen in TVB's Z3801A performance plots..

there are a good number of Z3801As modified to be 58503As on Ebay now. Got one from Yinxh some time ago, and that unit took over one year to fully settle down! Now I am consistently getting xE-013 ADEV from 0.1s to a couple 100s out of it. PN is excellent on that unit too.

bye,
Said

Sent From iPhone

On Jun 3, 2012, at 2:21, Rex <rexa at sonic.net> wrote:

> Said,
> 
> Thanks for the info and congrats on the stats from the Jackson Labs stuff.
> 
> You mentioned the older HP Z3801. I wonder if you (or others) happen to have comparison numbers on the Z3816A with the MTI 260 oscillator or the Z3805 with (I think) the same oscillator. I thought I heard the MTI 260 might be slightly better than the 10811 but can't recall if anyone here actually made measurements,
> 
> Not to say that any of the HP Z---- stuff is seen for sale often these days. But I have one of each of the above mentioned.
> 
> Guess it may be close to the *time* where I should take the *time* to build or set up a system where I could get trustworthy measurements of these *timing* quality things myself. I keep reading but never seem to find the time to actually do it.
> 
> -Rex
> 
> 
> On 6/3/2012 1:46 AM, SAIDJACK at aol.com wrote:
>> Jerry, Chris,
>> 
>> it's all relative, while the Lpro may be a good Rb standard, it's phase
>> noise is not that good really. You list:
>> 
>>    -96dBc/Hz @ 10Hz, -138dBc/Hz @ 100Hz, -152dBc/Hz @ 1KHz  offsets
>> 
>> For the Lpro. The new Jackson Labs Technologies LN CSAC GPSDO with SC-cut
>> phase noise and ADEV filter achieves the following:
>> 
>>    -138dBc/Hz @ 10Hz, -148dBc/Hz @ 100Hz, -152dBc/Hz @ 1KHz  offsets.
>> 
>> At 1Hz offset we see -105dBc/Hz and better on that unit.
>> 
>> The FEI-5680A Rubidium that we discussed here some time ago has a much
>> worse phase noise plot of course, because the 10MHz is generated digitally
>> through a DDS, not a 10MHz crystal oscillator..
>> 
>> It all depends on your requirements, and your budget.. I think the Z3801A
>> (or it's brother the 58503A) is still one of the lowest phase noise and
>> best ADEV GPSDO on the surplus market if you get a typical unit, and if you can
>>  locate one.
>> 
>> bye,
>> Said
>> 
>> From: Jerry Mulchin<_jmulchin at cox.net_ (mailto:jmulchin at cox.net)>
>> Date: June 2,  2012 16:44:14 PDT
>> To: Discussion of precise time and frequency  measurement
>> <_time-nuts at febo.com_ (mailto:time-nuts at febo.com)>
>> Subject:  Re: [time-nuts] GPS and Rubidium frequency standards and noise
>> question  (newbie).
>> Reply-To: Discussion of precise time and frequency  measurement
>> <_time-nuts at febo.com_ (mailto:time-nuts at febo.com)>
>> 
>> 
>> 
>> 
>> 
>> Chris,
>> 
>> To answer your question  regarding using a Rubidium standard as a frequency
>>  reference
>> for your  Transverters.
>> 
>> GPS really has nothing to do  the main requirement regarding Phase Noise
>> and  your
>> Transceivers. But the 10MHz oscillator inside the  Rubidium standard is the
>> item
>> that will be the Phase Noise  problem if you get the wrong Rubidium
>> standard. There
>> are  cheap Rubidiums and there are good Rubidium standards to  consider.
>> 
>> An LPRO-101 is actually a very  good Rubidium standard, and exhibits Phase
>> Noise
>> values of  -96dBc/Hz @ 10Hz, -138dBc/Hz @ 100Hz, -152dBc/Hz @ 1KHz  offsets
>> from carrier. This is what I use for my 10GHz  Transverter reference, but I
>> don't lock it
>> to GPS when in  the field. LPRO-101's can be gotten pretty  reasonably.
>> 
>> Locking the LPRO-101 to a GPS  will require more support circuitry, and
>> most of the
>> folks  on this list can help you with that.
>> 
>> Also,  Thunderbolt GPS disciplined units are nice, but I do not know the
>> Phase  Noise
>> numbers of a typical Thunderbolt unit. Others here  probably know the
>> answer to that.
>> 
>> The  important thing to remember is you don't what to use 10MHz oscillators
>> that  have
>> poor Phase Noise performance as it will effect your  weak signal capability
>> if you use
>> a poor Phase Noise  oscillator.
>> 
>> Jerry
>> 
>> At  03:05 PM 6/2/2012, you wrote:
>> 
>> If you want a frequency reference.  There is nothing better than GPS.  In
>> 
>> 
>> fact it you bought a Rubidium you would  still need the GPS so you could
>> 
>> 
>> calibrate its  frequency.
>> 
>> 
>> 
>> 
>> 
>> Some GPSes might be noisy but then you can  lock a good double oven crystal
>> 
>> 
>> oscillator to it and have what they call a  "GPS disciplined crystal
>> 
>> 
>> oscillator or "GPSDO".
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> On Sat, Jun 2, 2012 at 2:57 PM, Chris Wilson<_chris at chriswilson.tv_
>> (mailto:chris at chriswilson.tv)>   wrote:
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> I am looking to get a frequency standard  for my amateur radio shack,
>> 
>> 
>> 
>> 
>> initially for verifying test gear  readings, but later as a standard
>> 
>> 
>> 
>> 
>> to lock receiver and transmitter  oscillators to. I was going to buy
>> 
>> 
>> 
>> 
>> a GPS frequency standard but a friend  warned me these may have noise
>> 
>> 
>> 
>> 
>> issues when I come to use it with an  oscillator in RX / TX
>> 
>> 
>> 
>> 
>> applications. It's not something I had  considered, so what's the
>> 
>> 
>> 
>> 
>> score here please? Should I not buy a GPS  standard? Thanks. Any
>> 
>> 
>> 
>> 
>> links to known safe suitable purchase  sources from personal
>> 
>> 
>> 
>> 
>> experience welcome, either here or by PM  or e-mail. I am in the UK.
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> --
>> 
>> 
>> 
>> 
>> Best  regards,
>> 
>> 
>> 
>> 
>> Chris Wilson  _mailto:chris at chriswilson.tv_ (mailto:chris at chriswilson.tv)
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
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