[time-nuts] Soekris Net4801 vs NET4501 as Statum 1 timeserver

[Geoff Horner]

Thanks Poul for the info.

I will be getting the 4501 then.

I would like a copy of NTPns. Is the copy on your web page current?

I may end up using a FEI 5081a and M12+T  I already have with the 4501. I
can probably program the frequency of 5081a to what is required.

I'm looking forward to the M12M gps which I believe is out Dec this year.
Google alerts doesn't seem to find much each week on the arrival of this
unit.

Cheers

Geoff





----- Original Message -----
From: "Poul-Henning Kamp" <phk at phk.freebsd.dk>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Sent: Saturday, September 10, 2005 4:30 PM
Subject: Re: [time-nuts] Soekris Net4801 vs NET4501 as Statum 1 timeserver


> In message <002b01c5b5bf$8eda7670$0201010a at barney>, "Geoff Horner" writes:
> >Hi all,
> >
> >Does anyone know which of the two Soekris boards makes a better statum 1
> >time server.
>
> The net45xx series does because you can make hardware timestamps
> with it:
> http://phk.freebsd.dk/soekris/pps
>
> >Anyone used a OCXO in either?
>
> Yes, both.  Finding OCXO's with the oddball frequencies are the
> hardest bits.
>
> >I have seen phk's results of the 4501, although
> >that was tweaked at fair bit using an Rb oscillator.
>
> The timestamping performance would be the same without an Rb,
> even without using an OCXO you will get much better performance
> than with anything that needs interrupts to timestamp.
>
> Be aware that the normal NTPD can't really use this for anything,
> the PLL is not tuned for such precision work.
>
> I have writte from scratch NTP server called NTPns which is geared
> towards stratum-1 work with atomics etc, and you can have a copy
> if you want.
>
> This is the stability display from a net4501 with an ISOtemp OCXO131
> OCXO and a Oncore m12+T GPS:
>
> Source m12_0: votes 6.000000 flags <UTC> los 0/15 update 1 SELECTED
>         stratum 0 delay 0.000000000 dispersion 0.000000088 refid [47 50 53
00]
>         last_ts 1126340906.000000006 last_delta 0.000000007
>      1: 11111111 -0.000000046 1.391e-07
>      2: 11111111 -0.000000059 1.456e-07
>      4: 11111111 -0.000000052 7.344e-08
>      8: 11111111 -0.000000031 1.525e-08
>     16: 11111111 -0.000000036 4.834e-09
>     32: 11111111 -0.000000030 8.111e-09
>     64: 11111111  0.000000044 6.030e-10
>    128: 11111111  0.000000007 4.264e-10
>    256: 11111111  0.000000011 3.015e-10
>    512: 11111111  0.000000030 1.317e-10
>   1024: 11111111  0.000000028 8.538e-11
>   2048: 11111111 -0.000000013 1.013e-10
>   4096: 11111111 -0.000000012 4.363e-11
>   8192: 11111111 -0.000000024 3.043e-11
>  16384: 11111111  0.000000006 6.043e-12
>  32768: 11111111 -0.000000035 4.342e-12
>  65536: 11111111 -0.000000033 2.434e-12
> 131072: 11111111  0.000000002 6.655e-13
> 262144: 11111111  0.000000009 4.418e-13
> 524288: 11111111 -0.000000002 2.961e-13
>
> First column: integration time
> Second column: precense bitmap for 8 samples
> Third column: average offset [sec]
> Fourth column: Allan variance after discipline.
>
> --
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by
incompetence.
>
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