[time-nuts] Serial port splitter s/w

[paul swed]

Ummm think you sent the question to the wrong group perhaps?


On Wed, Feb 26, 2014 at 12:50 PM, <corcsal at yahoo.ca> wrote:

> I have some problems with My 8505A
> Analyzer, it has no RF output, I checked the YTO and other frequency
> dividers
> and it appears to be OK some times there is RF output only it will not
> tune and
> it seems to cut out as I tune trough the frequency range.
> Thank You
> Sal C. Cornacchia Electronic RF Engineer
> Ret.
>
>
>
> On Wednesday, February 26, 2014 12:33:17 PM, Chris Albertson <
> albertson.chris at gmail.com> wrote:
>
> It's not going to work.
>
> If the purpose of running the Thunderbolt is only to drive NTP then
> you don't need LH.  NTP's only tags the pulses to the nearest
> microsecond, nano sec on accuracy is lost on NTP.     I'd even say the
> TB is the wrong GPS for NTP.  It costs to much and uses to much power.
>
> But if you are also, or mainly, using the Thunderbolt for it's 10Mhz
> and NTP is a secondary function then a TB makes sense.
>
> Yes you NEED the PPS on the serial cable.   Thunderbolts do not send
> NMEA.  Thunderbolts send their own data format that is unique to
> Trimble.  Don't modify the GPS receiver.  Make a special cable
> adapter.   When you do this pay attention to polarity of the PPS
> signal.  It is easy to get it backwards.  You want the raising edge of
> the TB pulse to interrupt the computer.  It you invert the signal the
> wrong number of times the time will be "off" by the ouse length and I
> don't know if the pulse length is controlled to the level the leading
> edge is.    Remember RS232 uses negative and positive voltage, data
> lines use negative logic, control lines positive.   The TB's PPS is
> TTL level.   Many rs232 ports do accept t/l level if you get the
> polariy correct.
>
> Again don't even bother to run an NTP server without PPS.  You may as
> well just get time from some internet time servers.
>
> You can NOT control a GPS from two ports.  Both NTP and LH will try to
> send commands to the GPS.
>
> Likely, almost certainly you need to build a small circuit board the
> has two connectors that face the TB (PPS and serial) and one that
> faces the computer.  The little perfboard makes a neat way to or
> connect cables but you could solder up a y--cable
>
> The best thing to do is get a cheaper GPS, and one that uses less
> power to drive the NTP server.  The old Motorola Oncore series are
> cheap and the new breed of very small GPSes are good too.  DOn't spend
> more than $40 or $50 on a GPS to drive NTP as ,again NTP record
> microseconds.
>
> You could free up that Windows PC too.  It is not the best platform
> for NTP.  Asmall ARM based system (even the Rasbery Pi) will
> outperform a Windows based NTP server.  and use a LOT less power
> (Power cost for a NTP server is more than you think, it came to about
> $300 a year for me if I used a standard PC and a thunderbolt.
> Switching to a very tiny ARM based system and a smaller GPS gave as
> good performance and power savings paid for the hardware in 1/2 a
> year.  $.21/KWH about 170W and 8760 hours per year comes to a $300
> power bill.  My current system is powered by a 1000 mw plug-in power
> cube and does not need a cooling fan.
>
> On Wed, Feb 26, 2014 at 7:53 AM, David C. Partridge
> <david.partridge at perdrix.co.uk> wrote:
> > I'm running Meinberg NTP on the Windows 7 x64 machine to which my
> Thunderbolt is attached.
> >
> > I'd like to be able to share the serial port between LH and NTP so that
> I can run the machine as an NTP Stratum 1 server locked to the TB, and also
> be able to use LH to check things.
> >
> > I looked around the with Google, and saw *numerous" serial port
> splitters.  Which is recommended?
> >
> > Also what's the best way how to configure NTP to lock the the TB on a
> serial port?  Do I need to modify the TB to deliver the PPS down one of the
> serial data lines or will NTP work well by parsing the NMEA time messages?
> >
> > Many thanks
> > David Partridge
> >
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>
>
> --
>
> Chris Albertson
> Redondo Beach, California
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