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

KA2WEU at aol.com KA2WEU at aol.com
Thu Aug 11 21:06:28 EDT 2016

```-177dBm /Hz at 300 deg  SSB phase noise is correct, not because AM/  FM but
Single Sideband Energy .
In my last QEX paper I showed the measured AM and FM levels and how to
calculate them.

73 de Ulrich

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In a message dated 8/11/2016 9:00:11 P.M. Eastern Daylight Time,
mfeher at eozinc.com writes:

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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