simonpg wrote:
> So I have this fine receiver and have been a member of pool.ntp.org for
> several years. But I would like to take advantage of the PPS signal.
> The downside is that I have no idea where to start. The upside is that
> I can solder and read a simple schematic diagram. Any ideas?

GOES was a time service received from a handful of weather satellites;
while the antenna looks GPS-like, it's not a GPS. Unfortunately, the
GOES time service was turned off a while (maybe 18 months?) ago. While
there are sporadic reports of people receiving time from the satellites,
there is no traceability and any results are totally untrustworthy.

So, a neat box has turned into a paperweight...

John
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Thank you for responding. Please excuse me while I learn to work with
this interface. My comments are interspersed below:

Hal Murray wrote:
> In article <1156450631.842127.105780@74g2000cwt.googlegroups.c om>,
> "simonpg" writes:
> >So I have this fine receiver and have been a member of pool.ntp.org for
> >several years.
> Have you found the web page for the driver?
> http://www.cis.udel.edu/~mills/ntp/h...s/driver5.html
> (That may not be the latest one, it's just what google found for me.)
>

I guess I didn't make myself clear enough. The clock works great:

ntpq> peer
remote refid st t when poll reach delay offset
jitter
================================================== ============================
*TRUETIME(0) .TRUE. 0 l 29 64 377 0.000 1.233
1.901
-clepsydra.dec.c .GPS. 1 u 504 1024 377 56.294 16.420
0.023
-clock.xmission. .GPS. 1 u 567 1024 377 81.726 15.580
1.204
+bigben.cac.wash .USNO. 1 u 553 1024 377 46.023 15.031
2.000
-time-nw.nist.go .ACTS. 1 u 566 1024 377 36.026 20.802
0.702
+clock.sjc.he.ne .CDMA. 1 u 509 1024 377 54.394 15.218
0.100
LOCAL(0) .LOCL. 10 l 35 64 377 0.000 0.000
0.004

> Lots of info here:
> http://www.leapsecond.com/museum/468-dc/theory.htm
> That doesn't mention a PPS signal. It says the signal is 468 MHz
> so I wouldn't be surprised if a GPS antenna filtered that out.

Yup, it does, "4-5 A phase locked receiver is used to receive and
recover raw data from the satellite signal. The raw data is processed
by analog circuitry and then passed to a microprocessor for conversion
to useful outputs; among which are a visual display, one Hertz and one
kilo Hertz timing pulses." It's just a little hidden.

>
> The usual approach with a PPS signal is to connect it to
> one of the RS-232 modem control signals. (I forget which one, but
> it should be easy to find.) Most of the PPS signals are TTL levels

DCD (Data Carrier Detect)

> rather than RS-232. If you want to get fancy you can wire up a
> level converter (MAX-232) type chip but it will almost-for-sure
> work with a direct connection. You do have to get the inversion
> right though - MAX-232 type chips are inverters. Software can
> normaly use either.
>

So, both the 1 and the 1K Hz pulses are available in the form of a BNC
connector. I know that TTL stands for Transistor To Transistor Logic,
but I don't know if that looks like a BNC connector.

> Once you get the signal into your box, try the ATOM (aka PPS) driver.
>
> Is GEOS still working? I found this note from June 2005 saying it
> was going off the air:
> http://www.febo.com/pipermail/time-n...ne/001050.html
>

I guess GOES is indeed dead, but we have GPS now. Truetime came out
with a replacement antenna that converted the GPS signal to something
that makes the 486-DC happy, so I am happy.

>
> --
> The suespammers.org mail server is located in California. So are all my
> other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
> commercial e-mail to my suespammers.org address or any of my other addresses.
> These are my opinions, not necessarily my employer's. I hate spam.

Thank you for your response! My comments are interspersed below.

John Ackermann N8UR wrote:
> simonpg wrote:
> > So I have this fine receiver and have been a member of pool.ntp.org for
> > several years. But I would like to take advantage of the PPS signal.
> > The downside is that I have no idea where to start. The upside is that
> > I can solder and read a simple schematic diagram. Any ideas?
>
> GOES was a time service received from a handful of weather satellites;
> while the antenna looks GPS-like, it's not a GPS. Unfortunately, the
> GOES time service was turned off a while (maybe 18 months?) ago. While
> there are sporadic reports of people receiving time from the satellites,
> there is no traceability and any results are totally untrustworthy.
>
> So, a neat box has turned into a paperweight...
>

It would have had Truetime not come out with a replacement antenna that
does a GPS to GOES conversion:

ntpq> peer
remote refid st t when poll reach delay offset
jitter
================================================== ============================
*TRUETIME(0) .TRUE. 0 l 50 64 377 0.000 2.831
1.619
-clepsydra.dec.c .GPS. 1 u 158 1024 377 56.722 17.000
0.222
+clock.xmission. .GPS. 1 u 220 1024 377 79.953 14.986
0.955
-bigben.cac.wash .USNO. 1 u 210 1024 377 42.859 15.810
0.323
-time-nw.nist.go .ACTS. 1 u 222 1024 377 36.091 21.114
1.429
+clock.sjc.he.ne .CDMA. 1 u 161 1024 377 53.454 15.612
0.382
LOCAL(0) .LOCL. 10 l 2 64 377 0.000 0.000
0.004

So it should still be a neat box.

> John
> _______________________________________________
> questions mailing list
> questions@lists.ntp.isc.org
> https://lists.ntp.isc.org/mailman/listinfo/questions

>So, both the 1 and the 1K Hz pulses are available in the form of a BNC
>connector. I know that TTL stands for Transistor To Transistor Logic,
>but I don't know if that looks like a BNC connector.

TTL is the electrical signal level. BNC is the mechanical connector.

You need to build a cable that has a BNC connector on one end
and a DB-9 on the other.

You can add the PPS signal to the existing serial cable if you want
or use a separate serial port.

If your existing cable has a molded plug you can't easily add it.
You can either chop the plug off and add a new one, or make an
adapter cable with two plugs, one of each sex, merging the PPS
in on one end.

--
The suespammers.org mail server is located in California. So are all my
other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's. I hate spam.

Hacking up a serial cable is no problem. I'm just worried about frying
something inside the 486-DC. Could I expect to see an LED lighting up
on one of those RS-232 signal testers? How about a Volt/Ohm Meter? Or
am I worring about nothing? So I'll hook the ring of the BNC to pin 1
of the DB-9, and the tip to whatever DCD is? Do I need to worry about
ground loops if I use the same serial port? (whine, whine, whine)
It's just hard to get the 486-DC fixed; know what I mean?

Hal Murray wrote:
> >So, both the 1 and the 1K Hz pulses are available in the form of a BNC
> >connector. I know that TTL stands for Transistor To Transistor Logic,
> >but I don't know if that looks like a BNC connector.
>
> TTL is the electrical signal level. BNC is the mechanical connector.
>
> You need to build a cable that has a BNC connector on one end
> and a DB-9 on the other.
>
> You can add the PPS signal to the existing serial cable if you want
> or use a separate serial port.
>
> If your existing cable has a molded plug you can't easily add it.
> You can either chop the plug off and add a new one, or make an
> adapter cable with two plugs, one of each sex, merging the PPS
> in on one end.
>
> --
> The suespammers.org mail server is located in California. So are all my
> other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
> commercial e-mail to my suespammers.org address or any of my other addresses.
> These are my opinions, not necessarily my employer's. I hate spam.

In article <1156547281.444666.212940@h48g2000cwc.googlegroups. com>,
"simonpg" writes:
>Hacking up a serial cable is no problem. I'm just worried about frying
>something inside the 486-DC. Could I expect to see an LED lighting up
>on one of those RS-232 signal testers? How about a Volt/Ohm Meter? Or
>am I worring about nothing? So I'll hook the ring of the BNC to pin 1
>of the DB-9, and the tip to whatever DCD is? Do I need to worry about
>ground loops if I use the same serial port? (whine, whine, whine)
>It's just hard to get the 486-DC fixed; know what I mean?

You can sanity check the ground loop problem with a voltmeter.

A scope would be a better tool for checking the PPS signal.
A meter might show something, but I'd expect troubles from
the long averaging times.

You could also put the scope/meter on the input to the DCD pin
to make sure you have an input rather than an output. It's
probably pulled up to a few volts. Look at others to see
what an output signal looks like.

--
The suespammers.org mail server is located in California. So are all my
other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's. I hate spam.