[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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