[time-nuts] State of the art of crystal oscillator measurements

[Mike Feher]

That is interesting. We always used -174 and not -177 as it was concluded that at those low levels AM and PM noise are not discernible, so, the total noise density per Hz was -174. This must be relatively new since I worked in industry. We had a bunch of PhDs from Lincoln helping as well and they always used -174. This sounds like one of those instrument manufacturers gimmick to make the numbers look better :). 

Your last statement is why I started to question the claims initially. - 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 [mailto:time-nuts-bounces at febo.com] On Behalf Of John Miles
Sent: Thursday, August 11, 2016 7:57 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] State of the art of crystal oscillator measurements

-177 = the -174 dBm/Hz SSB thermal noise floor at 25C, less 3 dB to account for the usual assumption that half of it is AM, half PM.   

dBm/Hz is obviously equivalent to dBc/Hz for a 0 dBm carrier.  

Anyone who claims to measure noise in a 1 Hz bandwidth below -177 dBm/Hz at room temperature is either doing something wrong somewhere, or doing something amazing somewhere.

-- john, KE5FX
Miles Design LLC

> -----Original Message-----
> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Mike 
> Feher
> Sent: Thursday, August 11, 2016 4:15 PM
> To: 'Discussion of precise time and frequency measurement'
> Subject: Re: [time-nuts] State of the art of crystal oscillator 
> measurements
> 
> That is why I asked what the Po was. Where did the 177 come from? L(f) 
> is single sided. This is not my first "rodeo" in these matters. 73 - 
> Mike
> 
> Mike B. Feher, EOZ Inc.
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960 office
> 908-902-3831 cell
> 

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