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

[SAIDJACK at aol.com]

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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-- 





Chris Albertson


Redondo Beach,  California


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Jerry  Mulchin



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