[time-nuts] time-nuts Digest, Vol 111, Issue 70

Frank Hughes hp_ciscovss at yahoo.com
Sun Oct 27 00:31:28 UTC 2013



Discretion being the better part of valor, and I need plug & play for this piece, in order to save time for other things that need attention, so I ordered :
 "Symmectricom  58535A"

After I got the Fury working, noted an interesting anomaly (that turned out to be my fault, but interesting) 

Connected the 10Mhz from the Fury to the HP 5087A distribution amp feeding 10Mhz to all the HP and Agilent equipment needing a stable reference. 

One of the ancient HP things ( 59309A) said it had no 10Mhz external oscillator!
The 59309A worked w/ the Trimble, not the Fury.

Did some troubleshooting, the Fury 10Mhz signal is about 2 or 3 db less than the Trimble.

This attenuation was enough to prevent the 59309A from locking on to the signal. 
All the other HP and Agilent worked fine with either 10Mhz source.

I remembered that I had been too lazy to actually set the no-load voltage on each of the 5087A output amplifiers
the last time I had it apart.
 
So I pulled the 5087A out of the rack, took the cover off and and set the levels correctly.  59309A happy.

Anyway, when I finished all that, went to see how to get both the Trimble and Fury operating in parallel. 

- Trimble feeds 1PPS to the FreeBSD NTP server via the "FAT PPS" serial port circuit.
- Fury feeds the HP 5087A distribution amp for all the HP/Agilent to sync to.

The FAT PPS won't fit on the Fury, Fury=male null modem DB9, TB=Female straight DB9.

So I will use both GPSDO boxes.  Which led me to the splitter..........

73 and thank again for the great ideas!
Frank
KJ4OLL





On Saturday, October 26, 2013 5:49 PM, "time-nuts-request at febo.com" <time-nuts-request at febo.com> wrote:
 
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Today's Topics:

   1. Re: Splitter for GPS antenna suggestions? (Tom Knox)
   2. Re: Splitter for GPS antenna suggestions? (Bob Camp)
   3. Re: Splitter for GPS antenna suggestions? (Magnus Danielson)
   4. Re: Splitter for GPS antenna suggestions? (Brooke Clarke)
   5. Re: Time stamping with a PICPET (Chris Albertson)
   6. Re: Time stamping with a PICPET (Hal Murray)
   7. Re: Splitter for GPS antenna suggestions? (Charles Steinmetz)


----------------------------------------------------------------------

Message: 1
Date: Sat, 26 Oct 2013 10:54:40 -0600
From: Tom Knox <actast at hotmail.com>
To: Time-Nuts <time-nuts at febo.com>
Subject: Re: [time-nuts] Splitter for GPS antenna suggestions?
Message-ID: <COL130-W31BAE6E1605519EB154C97DF0E0 at phx.gbl>
Content-Type: text/plain; charset="iso-8859-1"

I think this discussion could use some parity. Some many options have been presented. But to return to one of the first posts, I would buy a Symmetricom Splitter on eBay. They have really become the industry standard and can be had for a reasonable price. There are certainly products that could be selected to meet your needs for less money but it will have some compromises, and there are others that could meet or perhaps even exceed Symmetricoms performance but are usually more money and are much less common on the surplus market. I would buy one with more ports then you need in case you ever want to test or install an additional GPS receivers. Remember "If you buy the best you only cry once"

Thomas Knox



> From: lists at rtty.us
> Date: Sat, 26 Oct 2013 08:00:32 -0400
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] Splitter for GPS antenna suggestions?
> 
> Hi
> 
> Pretty much all of the MiniCircuits splitters seem to happily pass DC. The same is true of all of the TV splitters I've tried. The standard circuits (as in the lowest cost) have a transformer or transmission line that has no DC path to ground.
> 
> Bob
>  
> On Oct 26, 2013, at 12:58 AM, David <okdavid5555 at cox.net> wrote:
> 
> > Hello --
> > 
> > I'm not very knowledgeable electronically, but I am currently using a
> > Minicircuits ZAPD-3DB-1575-3 splitter to connect one TrueTime 142-400 GPS
> > antenna to a Spectracom 8183 and a Spectracom 8183-A. I use the Spectracoms
> > only as precise digital clocks, and they seem to work just fine.
> > 
> > I bought the Minicircuits splitter on eBay for $30, buy-it-now, as I recall,
> > but it's been a while ago.
> > 
> > Hope that's helpful.
> > 
> > David in Oklahoma City
> > 
> > -----Original Message-----
> > From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> > Behalf Of Frank Hughes
> > Sent: Friday, October 25, 2013 5:31 PM
> > To: time-nuts at febo.com
> > Subject: [time-nuts] Splitter for GPS antenna suggestions?
> > 
> > Hi,
> > I want to see if it is possible to feed both the Trimble TB and the Jackson
> > Labs Fury from the existing antenna. It appears both the TB and the Fury are
> > 5vdc antenna power. 
> > 
> > Checked the auction site for splitters, but before I randomly buy anything,
> > could someone please suggest what they use that works?
> > 
> > Thanks, and 73
> > Frank
> > KJ4OLL
> > _______________________________________________
> > time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
> > 
> > _______________________________________________
> > time-nuts mailing list -- time-nuts at febo.com
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> 
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------------------------------

Message: 2
Date: Sat, 26 Oct 2013 13:22:56 -0400
From: Bob Camp <lists at rtty.us>
To: Discussion of precise time and frequency measurement
    <time-nuts at febo.com>
Subject: Re: [time-nuts] Splitter for GPS antenna suggestions?
Message-ID: <EA8028DE-F5AA-4003-B6AC-092F4FDC3B25 at rtty.us>
Content-Type: text/plain; charset=us-ascii

Hi

The Symmetricom / HP splitters are way more than just a splitter. They have an amp and some filtering in addition to the split. They also pass DC from only one port and correctly DC terminate the other ports so you don't get an "antenna missing" error.

Bob

On Oct 26, 2013, at 12:54 PM, Tom Knox <actast at hotmail.com> wrote:

> I think this discussion could use some parity. Some many options have been presented. But to return to one of the first posts, I would buy a Symmetricom Splitter on eBay. They have really become the industry standard and can be had for a reasonable price. There are certainly products that could be selected to meet your needs for less money but it will have some compromises, and there are others that could meet or perhaps even exceed Symmetricoms performance but are usually more money and are much less common on the surplus market. I would buy one with more ports then you need in case you ever want to test or install an additional GPS receivers. Remember "If you buy the best you only cry once"
> 
> Thomas Knox
> 
> 
> 
>> From: lists at rtty.us
>> Date: Sat, 26 Oct 2013 08:00:32 -0400
>> To: time-nuts at febo.com
>> Subject: Re: [time-nuts] Splitter for GPS antenna suggestions?
>> 
>> Hi
>> 
>> Pretty much all of the MiniCircuits splitters seem to happily pass DC. The same is true of all of the TV splitters I've tried. The standard circuits (as in the lowest cost) have a transformer or transmission line that has no DC path to ground.
>> 
>> Bob
>> 
>> On Oct 26, 2013, at 12:58 AM, David <okdavid5555 at cox.net> wrote:
>> 
>>> Hello --
>>> 
>>> I'm not very knowledgeable electronically, but I am currently using a
>>> Minicircuits ZAPD-3DB-1575-3 splitter to connect one TrueTime 142-400 GPS
>>> antenna to a Spectracom 8183 and a Spectracom 8183-A. I use the Spectracoms
>>> only as precise digital clocks, and they seem to work just fine.
>>> 
>>> I bought the Minicircuits splitter on eBay for $30, buy-it-now, as I recall,
>>> but it's been a while ago.
>>> 
>>> Hope that's helpful.
>>> 
>>> David in Oklahoma City
>>> 
>>> -----Original Message-----
>>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>>> Behalf Of Frank Hughes
>>> Sent: Friday, October 25, 2013 5:31 PM
>>> To: time-nuts at febo.com
>>> Subject: [time-nuts] Splitter for GPS antenna suggestions?
>>> 
>>> Hi,
>>> I want to see if it is possible to feed both the Trimble TB and the Jackson
>>> Labs Fury from the existing antenna. It appears both the TB and the Fury are
>>> 5vdc antenna power. 
>>> 
>>> Checked the auction site for splitters, but before I randomly buy anything,
>>> could someone please suggest what they use that works?
>>> 
>>> Thanks, and 73
>>> Frank
>>> KJ4OLL
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>> 
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>                           
> _______________________________________________
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------------------------------

Message: 3
Date: Sat, 26 Oct 2013 19:52:41 +0200
From: Magnus Danielson <magnus at rubidium.dyndns.org>
To: Discussion of precise time and frequency measurement
    <time-nuts at febo.com>
Subject: Re: [time-nuts] Splitter for GPS antenna suggestions?
Message-ID: <526C0169.6010605 at rubidium.dyndns.org>
Content-Type: text/plain; charset=ISO-8859-1

On 10/26/2013 07:22 PM, Bob Camp wrote:
> Hi
>
> The Symmetricom / HP splitters are way more than just a splitter. They have an amp and some filtering in addition to the split. They also pass DC from only one port and correctly DC terminate the other ports so you don't get an "antenna missing" error.
Both good points. The added filtering means increased selectivity, which
translates to better resistance to RF power emissions outside of the
2,046 MHz bandwidth.

Wideband splitters does not have that benefit, but has it's use if you
can live with it.

Cheers,
Magnus


------------------------------

Message: 4
Date: Sat, 26 Oct 2013 11:16:21 -0700
From: Brooke Clarke <brooke at pacific.net>
To: Frank Hughes <hp_ciscovss at yahoo.com>,    Discussion of precise time
    and frequency measurement <time-nuts at febo.com>
Subject: Re: [time-nuts] Splitter for GPS antenna suggestions?
Message-ID: <526C06F5.3020509 at pacific.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Hi Frank:

I've used TV splitters and in line amplifiers, see:
http://www.prc68.com/I/4GPS.shtml

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html

Frank Hughes wrote:
> Hi,
> I want to see if it is possible to feed both the Trimble TB and the Jackson Labs Fury from the existing
> antenna.
> It appears both the TB and the Fury are 5vdc antenna power.
>
> Checked the auction site for splitters, but before I randomly buy anything, could someone please suggest what they use that works?
>
> Thanks, and 73
> Frank
> KJ4OLL
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>
>



------------------------------

Message: 5
Date: Sat, 26 Oct 2013 12:02:43 -0700
From: Chris Albertson <albertson.chris at gmail.com>
To: Tom Van Baak <tvb at leapsecond.com>,     Discussion of precise time and
    frequency measurement <time-nuts at febo.com>
Subject: Re: [time-nuts] Time stamping with a PICPET
Message-ID:
    <CABbxVHuAYRn+AjXc6x8PRbPM2rxWK-HJ3vdvVGCtkGfxNqwWAg at mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1

Good idea but you assume NTP could generate a pule with better accuracy
then it can measure them.   That is likely not true.  On a modern system we
can mures puss with about +/- 2 uSec jitter.  We can not export a clock
with that level of precision.

The reason is that all the normal outputs get queued while the DCD
interrupt works better than you'd think.    Also we don't need to fix it
because the weal link is transferring tine OUT of the system over the
network


On Sat, Oct 26, 2013 at 1:37 AM, Tom Van Baak <tvb at leapsecond.com> wrote:

> > What kind of accuracy do the picket's have.   You can log pulses using
> the
> > PPS system on bare PC hardware and get the time of the pulse logged to
> > within about 2 uSec.  Simply connect the pulse to DCD line of a real
> serial
> > port.
> >
> > If you need better than 2 uSec then yes you need external hardware.
>
> The current version of picPET is 400 ns resolution given a 10 MHz clock.
> It was designed for applications needing millisecond- to microsecond-level
> accuracy. Not bad for a $1 8-pin chip.
>
> > If those pickets are much better than 2 uSec then they make a GREAT front
> > end for a NTP server.  Question: how do you transfer accurate time into
> the
> > PIC?
>
> They are a form of T2D or TDC (time to digital converter) or TSC
> (continuous time-stamping counter) for making zero-dead time measurements,
> not real-time clocks for the purpose of maintaining time of day, or day or
> year.
>
> If all you need is a 1PPS source use a GPS timing receiver, or a GPSDO
> with 1 PPS output, or a 10 MHz external clock and a picDIV divider. See
> http://leapsecond.com/pic/ for many different dividers.
>
> ----
>
> As far as NTP is concerned, I wonder if you've ever considered turning the
> tables on how it works. AFAIK, NTP gets an external time reference (e.g.,
> 1PPS) as an interrupt. With modern computers, this is horrible. There are
> far too may layers of h/w jitter (pipelines, multiple levels of cache, TLB
> misses, etc.) and s/w jitter (interrupt handling, spinlocks, interrupt
> masking, priority levels, etc.).
>
> For best timing, perhaps a better solution is not to have NTP receive a
> 1PPS as *input* and try to pretend to measure it internally in s/w but for
> NTP to *output* a 1PPS and measure that externally with sub-microsecond h/w
> (like a picPET).
>
> That bypasses all the jitter associated with asynchronous events;
> replacing it instead with a synchronous event. If NTP takes an internal s/w
> timestamp before and after the pulse is output, and you obtain (via serial
> port) the timestamp reading made by external h/w you can then correct the
> NTP paper clock, with far less h/w and s/w jitter.
>
> The mental shift is to stop treating a PC+NTP as a precise clock and pulse
> measurement instrument and start treating a PC+NTP as a precise clock and
> pulse generation instrument.
>
> /tvb
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>



-- 

Chris Albertson
Redondo Beach, California


------------------------------

Message: 6
Date: Sat, 26 Oct 2013 14:47:01 -0700
From: Hal Murray <hmurray at megapathdsl.net>
To: Tom Van Baak <tvb at LeapSecond.com>,    Discussion of precise time and
    frequency measurement <time-nuts at febo.com>
Subject: Re: [time-nuts] Time stamping with a PICPET
Message-ID:
    <20131026214701.48962406071 at ip-64-139-1-69.sjc.megapath.net>
Content-Type: text/plain; charset=us-ascii


tvb at LeapSecond.com said:
> As far as NTP is concerned, I wonder if you've ever considered turning the
> tables on how it works. AFAIK, NTP gets an external time reference (e.g.,
> 1PPS) as an interrupt. With modern computers, this is horrible. There are
> far too may layers of h/w jitter (pipelines, multiple levels of cache, TLB
> misses, etc.) and s/w jitter (interrupt handling, spinlocks, interrupt
> masking, priority levels, etc.).

You have to have your time-nut hat on before that makes a difference.

Has anybody measured it?  It should be easy to hack the kernel PPS interrupt 
routine to flap a printer port signal and measure the delay between the PPS 
signal and printer port.


> For best timing, perhaps a better solution is not to have NTP receive a 1PPS
> as *input* and try to pretend to measure it internally in s/w but for NTP to
> *output* a 1PPS and measure that externally with sub-microsecond h/w (like a
> picPET). 

The Trimble Palisade and Acutime work that way.



-- 
These are my opinions.  I hate spam.





------------------------------

Message: 7
Date: Sat, 26 Oct 2013 17:47:26 -0400
From: Charles Steinmetz <csteinmetz at yandex.com>
To: Discussion of precise time and frequency measurement
    <time-nuts at febo.com>
Subject: Re: [time-nuts] Splitter for GPS antenna suggestions?
Message-ID: <20131027014729.lSFivOqZ at smtp4h.mail.yandex.net>
Content-Type: text/plain; charset="us-ascii"; format=flowed

Bob wrote:

>The Symmetricom / HP splitters are way more than just a splitter. 
>They have an amp and some filtering in addition to the split. They 
>also pass DC from only one port and correctly DC terminate the other 
>ports so you don't get an "antenna missing" error.

And they were designed for precision timing systems, so thought was 
given to minimum propagation time and to equal delay between 
channels.  PT is about 20nS, and very consistent channel-to-channel.

Best regards,

Charles





------------------------------

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