[ntp:questions] Inexpensive home reference clock - WWVB/CDMA?

[Pete Stephenson]

As a time geek, I've been looking at getting either a WWVB or CDMA
reference source to provide timing to my network here at home, and to
the NTP pool.

Due to my location (apartment complex, first floor) I have no roof
access and poor GPS signal through the window, so GPS timing is out.

I've considered making a WWVB receiver, but I'm a time geek, not an
electronics geek, and would spend more on necessary things (soldering
iron, for example) than it'd cost for me to buy a commercial product.

There are two possible commercial products I'm looking at: Beagle
Software's ClockWatch Radio Sync (WWVB receiver, $199.95) and Cell Sync
(CDMA, $649.95). Alas, neither of them are available on eBay for cheap.

Does anyone have any experience with either? I presume that when
connected to an RS-232 serial port that NTPv4 should have no trouble
getting time from either.

I'm looking at the Radio Sync clock, simply because I'm a Cheap
Bastard(tm) and don't have much money to spend. This would be more than
adequate for my purposes, and I believe it would be adequate for
providing time to the NTP pool. Is there any reason why I should not
deploy a WWVB clock to the NTP pool or advertise it as a stratum 1
server for public use? While it might not provide as precise a time
signal as CDMA or GPS references, it should be well within the margin of
error for internet based timekeeping, right?

That said, does anyone happen to have any surplus WWVB or CDMA clocks
lying around that they'd consider selling to a fellow time geek?

Cheers!

[Jason Rabel]

What GPS antenna did you use? Was it passive or +5V? What was the rated dB
gain? Did you try sticking the antenna a few inches out past your window?
Sometimes you can increase your signal dramatically just by doing that. Also
depending on where you live if you only have a partial view you want it to
face towards the equator for the most satellites.

Maybe you could make friends with the person on the top floor and they would
let you mount an antenna on a PVC pipe outside their balcony which would get
you a clear view of the sky then you can just run the cable down the outside
wall into your apt.

WWVB receivers will sometimes pop up on eBay, usually the older TrueTime
models. With those the serial output can be set to once a second which NTP
can then read in. For the best accuracy you should use the PPS signal too,
however that is only supported in FreeBSD, Solaris, and Linux (with kernel
patching).

IIRC, NTP will support WWV (not WWVB) via an audio input to your sound card.
This is a DIY project, I've seen a couple on the net and it doesn't seem to
require too much assembly, just finding the right parts (antenna) could be
the challenge.

I'm unsure about the RadioSync and NTP, best thing would be to contact them
about it or read more on their site, I'm sure they get that question all the
time. $199 for a modern timing receiver like that seems quite reasonable.

Another hurdle might be interference with the WWVB signal, but without
having any equipment to test beforehand you are kind of diving in blind. A
CDMA receiver you can test beforehand just seeing how good of a signal you
get with your cell phone.

Jason

Post by Pete Stephenson
As a time geek, I've been looking at getting either a WWVB or CDMA
reference source to provide timing to my network here at home, and to
the NTP pool.
Due to my location (apartment complex, first floor) I have no roof
access and poor GPS signal through the window, so GPS timing is out.
I've considered making a WWVB receiver, but I'm a time geek, not an
electronics geek, and would spend more on necessary things (soldering
iron, for example) than it'd cost for me to buy a commercial product.
There are two possible commercial products I'm looking at: Beagle
Software's ClockWatch Radio Sync (WWVB receiver, $199.95) and Cell Sync
(CDMA, $649.95). Alas, neither of them are available on eBay for cheap.
Does anyone have any experience with either? I presume that when
connected to an RS-232 serial port that NTPv4 should have no trouble
getting time from either.
I'm looking at the Radio Sync clock, simply because I'm a Cheap
Bastard(tm) and don't have much money to spend. This would be more than
adequate for my purposes, and I believe it would be adequate for
providing time to the NTP pool. Is there any reason why I should not
deploy a WWVB clock to the NTP pool or advertise it as a stratum 1
server for public use? While it might not provide as precise a time
signal as CDMA or GPS references, it should be well within the margin of
error for internet based timekeeping, right?
That said, does anyone happen to have any surplus WWVB or CDMA clocks
lying around that they'd consider selling to a fellow time geek?

[Pete Stephenson]

In article <000201c7bc28$9d92dd30$0a00a8c0 at Inspiron>,

Post by Jason Rabel
What GPS antenna did you use? Was it passive or +5V? What was the rated dB
gain? Did you try sticking the antenna a few inches out past your window?
Sometimes you can increase your signal dramatically just by doing that. Also
depending on where you live if you only have a partial view you want it to
face towards the equator for the most satellites.

All I have is a handheld GPS navigation system (Garmin eTrex). The
window in my apartment faces another building about 15 feet away, and
there's an overhanging roof. There's a sliver of sky coverage, and some
signal makes it through the roof, but it's really not much. Sometimes
there's moderate coverage from 3 satellites, while other times there's
none at all.

Post by Jason Rabel
Maybe you could make friends with the person on the top floor and they would
let you mount an antenna on a PVC pipe outside their balcony which would get
you a clear view of the sky then you can just run the cable down the outside
wall into your apt.

Apartment management doesn't take kindly to stuff like that, and the
balcony is outside their front door (relatively small studios), so
there's not really any sky coverage either (see the overhanging roof
part above).

Post by Jason Rabel
I'm unsure about the RadioSync and NTP, best thing would be to contact them
about it or read more on their site, I'm sure they get that question all the
time. $199 for a modern timing receiver like that seems quite reasonable.

Indeed, that's what I was thinking. I'll drop them a line, but I'm a big
fan of saving money and buying used where possible. That, and letting
someone else take the first step and see if there's any problems. I've
not heard of Beagle until today, so it'd be nice to see if anyone else
has any experience with them.

Post by Jason Rabel
Another hurdle might be interference with the WWVB signal, but without
having any equipment to test beforehand you are kind of diving in blind. A
CDMA receiver you can test beforehand just seeing how good of a signal you
get with your cell phone.

My CDMA phone gets full or almost full signal strength here, so there's
no issues with that here. Still, the WWVB clock is significantly
cheaper, and I'm perpetually tight on money.

[Hal Murray]

Post by Pete Stephenson
My CDMA phone gets full or almost full signal strength here, so there's
no issues with that here. Still, the WWVB clock is significantly
cheaper, and I'm perpetually tight on money.

Where are you located relative to Colorado?

I tried one of the Maplin some-assembly-required WWVB receivers.
I couldn't get enough signal for useful timekeeping. I'm in California.

I never got around to double checking the tuning.

[Jason Rabel]

Post by Pete Stephenson
All I have is a handheld GPS navigation system (Garmin eTrex). The
window in my apartment faces another building about 15 feet away, and
there's an overhanging roof. There's a sliver of sky coverage, and some
signal makes it through the roof, but it's really not much. Sometimes
there's moderate coverage from 3 satellites, while other times there's
none at all.
Apartment management doesn't take kindly to stuff like that, and the
balcony is outside their front door (relatively small studios), so
there's not really any sky coverage either (see the overhanging roof
part above).

Okay, that's pretty understandable situation. I don't know how sensitive
those devices are, but you could try a high-gain timing antenna (I think
they are rated at like 38dB gain - usually about $40 on eBay) with a timing
receiver (I've seen the Motorola VP for $8 on eBay). Once your 3D position
is determined then all you would need is one satellite for timing.

If you still have long outages then you could get a GPSDO package which will
'flywheel' via an ovenized oscillator when there are no satellites.

That's my last thoughts on GPS. I won't keep trying to push the issue. ;)

Post by Pete Stephenson
My CDMA phone gets full or almost full signal strength here, so there's
no issues with that here. Still, the WWVB clock is significantly
cheaper, and I'm perpetually tight on money.

I was looking at their CDMA product after I replied before, and it looks
like it uses a pretty cheap Multitech modem (which I've seen sell on eBay
for $10). The problem with that modem (and many other cheap ones) is they
only give time down to the second, and it is a polling command. So while
more expensive, it seems to provide a lesser quality of time (you could do
better with NTP over the Internet or ACTS). Those people say .1 second
accuracy, which is probably just from continuously polling the modem and
finding when the time changes. Really it's not going to provide that great
of a time, I've seen better CDMA products though they are more expensive
(and you wanted cheap).

Again, your OS is going to be somewhat of a factor here. If you are running
windows, I don't know which builds support which reflocks (if any). If you
are running BSD, Linux, or Solaris then you should be pretty safe.

You can see what their return policy is, so if the WWVB unit doesn't work
out you can return it without a fuss (hopefully). Or you could get one of
those WWVB wall / desk clocks and see if it gets a signal and syncs up (plus
give you a clock that's always on-time around the house).

If you have a half-decent broadband connection you should be able to get
~100ms or better time via NTP over the Internet.

[Pete Stephenson]

In article <000001c7bc3a$16717d90$0a00a8c0 at Inspiron>,

Post by Jason Rabel
Okay, that's pretty understandable situation. I don't know how sensitive
those devices are, but you could try a high-gain timing antenna (I think
they are rated at like 38dB gain - usually about $40 on eBay) with a timing
receiver (I've seen the Motorola VP for $8 on eBay). Once your 3D position
is determined then all you would need is one satellite for timing.
If you still have long outages then you could get a GPSDO package which will
'flywheel' via an ovenized oscillator when there are no satellites.
That's my last thoughts on GPS. I won't keep trying to push the issue. ;)

Interesting. The Motorola VP is available for about $8 on eBay right
now, but it requires various electronic assembly to get it to interface
with the computer.

The TAPR TAC-2 kit (sadly, now discontinued) looks like an ideal thing
to do, but they don't make it anymore. I'd definitely be interested in
buying such a kit (with a bit of a premium for already-assembled,
ready-to-connect ones) if anyone here has one. If someone has such a
system they'd be willing to sell, drop me an email.

I might be able to swing GPS with such a high-gain antenna, and that'd
probably be preferable to other options as I'm looking to eventually put
such a system up on the NTP pool or listed as a public server -- if the
Beagle solutions are accurate only to 0.1 seconds, that's clearly
insufficiently accurate for my needs.

As for the OS, I currently run Windows on one machine, but have been
toying around with various flavors of Linux (Ubuntu and Debian,
particularly) in a Virtual Machine to see which one I'd like better. I'd
assume that since Ubuntu is based off of Debian, it'd work well...though
probably not in a VM.

[David J Taylor]

Pete Stephenson wrote:
[]

Post by Pete Stephenson
I've considered making a WWVB receiver, but I'm a time geek, not an
electronics geek, and would spend more on necessary things (soldering
iron, for example) than it'd cost for me to buy a commercial product.

[]

Post by Pete Stephenson
Cheers!

An easy to construct radio clock is described here:

http://www.buzzard.me.uk/jonathan/radioclock.html

Perhaps a friend could build it for you, or there may be an amateur radio
or electronics club in the area?

Cheers,
David

[jlevine]

Hello,

Post by Pete Stephenson
That said, does anyone happen to have any surplus WWVB or CDMA clocks
lying around that they'd consider selling to a fellow time geek?

You might consider using a standard modem and telephone line and
connecting to the NIST ACTS service. This service will provide an
accuracy
of a few milliseconds and a stablility of about 1 millisecond with a
periodic
30-second call to the NIST server in Colorado. It requires no outside
antenna
and no special hardware.
The details of the service are on the NIST web page:
tf.nist.gov. Look
for ACTS.
Judah Levine
Time and Frequency Division
NIST Boulder

[Pete Stephenson]

In article <1183641808.038169.289650 at i13g2000prf.googlegroups.com>,

Post by jlevine
You might consider using a standard modem and telephone line and
connecting to the NIST ACTS service.

Judah,

Good advice, and something I was considering. However, the only landline
telephone here is a VoIP phone, so there's no advantage to me using ACTS
over VoIP compared to NTP. Indeed, it'd probably be a disadvantage.

On a somewhat side note, thanks to you and anyone else who works to keep
the atomic clocks, ACTS, WWVB, and other NIST-provided time services up
and running. If you ever come out to Tucson, or I come to Boulder, I'll
buy you a beer or something.