[time-nuts] Need Time Help

Tom Van Baak tvb at LeapSecond.com
Tue Oct 4 11:25:01 EDT 2016

Hi Larry,

You are using a bunch of h/w and s/w together and you want each piece to maintain precise time.

Would it be possible for you to inject a very short GPS 1PPS pulse or GHz tone into your antenna feed?

That will cause a slight blip in your raw data which your processing s/w can then use to self-calibrate the absolute time of all samples as often as once a second. This allows your PC and OS to be data processors (which they are good at) and not precision timekeepers (which they are not good at). It also solves the latency issues with your SDR h/w and s/w.

I've done something similar with PC sound cards. Instead of having the OS pretend it's a timekeeper you just put a 1PPS into the R channel and your data stream into the L channel. It's trivial to then correlate the two and nail down the absolute time of the samples at the microsecond level. The beauty is that it completely avoids the problems of PC timekeeping. It works with any laptop and any operating system at any temperature and it also solves the accuracy and latency problems that even NTP on Linux doesn't solve.


----- Original Message ----- 
From: "Larry Hower" <hower at hower.net>
To: <time-nuts at febo.com>
Sent: Monday, October 03, 2016 9:41 PM
Subject: [time-nuts] Need Time Help

Hello to the List:

After a long and bitter struggle with XP and WIN 10, I am writing to ask
for some help in solving some problems we have been having in our attempt
to establish a very accurate time reference for use in EME activities.

We are hoping to achieve less than 5ms deviation, although anything below
15ms will be adequate for now.

Specifically, we want to use a universal reference that will enable amateur
radio operators in different parts of the world to start and stop their
transmissions within a few milliseconds of a specific time. For example, I
transmit at 12:00:00 for 1.75 minutes and “Joe” listens. Then “Joe”
transmits at 12:02:00 for 1.75 minutes. Repeat until QSO happens.

We are using WSJT-X software. We use standard receivers plus we have tried
a few SDRs.

Sorry for the oversimplified example but I want to make sure we are all on
the same page.

As background:

1. We are using desktops and laptops in separate locations running XP or
Win 10.

2. We have used MS clock tools, including use of Boulder time servers,
tried both host name and IP address, without reaching the goal.

3. We have set up some Serial GPS units with PPS and some USB GPS receivers
(no PPS) and can get to about 0.2 sec but it is not trusted or close enough.

4. We have set up a network time server with similar results.

5. Deviation is measured using WSJT-X


*Standard Receivers*

ICOMs (910/9100 and others – non-SDR). Locked to 10MHz external osc
reference. We have frequency accuracy of 1 to 2 Hertz at 10GHz.


We believe that SDR processing can insert a delay of varying length,
depending on the software, bandwidth, etc. Our SDR tests seem to have a
delay of as much as 0.5 sec. And with sometimes variable results. We will
see how SDRs can be used after we resolve the current issues.

*Some time related hardware details*

*1. Global Star 4 USB and Serial Connections*


We have 4 of these. Two are older models with serial connections. We have
serial ports on some computers (XP and a new high-end laptop running WIN
10) so we are able to activate the PPS option. Two of the GStar are newer
models with USB connections which are not able to use the PPS option.

We have tried NEMATime and NEMATime 2 software on this hardware without
reaching our goal of <15ms. Range of deviation is from 0.0 to about 0.3
sec. Drifts.  Deviation is measured using WSJT-X.

*2. TimeNet NTP Device*


We have one of these TimNet units and it has been set up at 2 different
locations on differing computers according to user instructions. We are
using the TimNet software as DL'd recently from their web site. We get GPS
“lock” and Time “lock” shown in the user panel but we do not have faith
that this is carried into the system clock. Occasionally the "lock"
indicators go blank but the time seems to be updated when the software is
strted again (the updated is operation is show at the correct time.  We
think the app needs some work. Deviation is measured using WSJT-X.  See
later details.


The G Star units have been installed at 2 separate locations, tested using
WSJT-X QRA 64 and WSPR-2 signals on 10.137MHz.

Similar tests with a TimeNet unit at one end and G Stars at the other end.

G Star units were installed on the XP laptops with the PPS option enabled
and running WSJT-X. These XP units seem to have their time “in sync”. See


We are not sure what, if any, internal delays there are attributable to
this software. We have been using the same version/build at both ends for
the tests. The software displays in 0.1 sec increments but will show 0.0sec
when things appear to be working well. We do not know the actual level of
precision of the WSJT-X software time measurements. I undersand that WSJT-X
“reads” the system clock at the start of a period (TX or RX) and displays
what it finds as the time deviation from the local system clock.


There are 2 laptops running XP. They seem to match each other re time using
WSJT-X, both are “out” usually by less than 0.1ms or 0.2ms. We are fairly
sure that they are working properly but they need to be more accurate

*WIN 10*

Installed on a number of desktop and laptop computers. Many efforts were
made to make these system clocks reference the GPS devices.

We became aware that the WIN Time/Date GUI was not always driving the
setting down into the system clock. We became aware also that the Registry
entries needed to be confirmed as far as NTP or local reference and the
sync cycle needed definition because of the same unreliable GUI actions.

We found that we needed to start the Time Services and deal with some other
factors.  We have found that in WIN 10 the time/date clock does not show
the update when it happens automatically according to the setting in the
directly.  It does how the correct time of sync when we do it manually or
restart the GUI.

The end result is that we don't trust WIN 10 and and we are not sure how to
fix the problem. Linux not allowed for now.


Our conclusion is that the external gear should be able to provide a more
accurate reference than we are able to obtain presently.  We think "it is
in there somewhere" but we can't get it out.

We have a feeling that the WIN system clocks are not being updated
correctly or at least in a repeatable manner.  We don't know if the problem
is hardwaare or software or our setup / configurations.

I ask for advice on how we can use the above gear or other gear or other
software to have our setup deliver better than 15ms accuracy.

Ultimately we want sub-millisecond accuracy.

Any help will be very much appreciated.  Thanks in advance for anything you
can advise.


Larry Hower


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