Discussion:
WWVB information
Add Reply
Doug Millar via time-nuts
2018-04-11 16:28:41 UTC
Reply
Permalink
Raw Message
Hi, My Spectracom 8161 comparator and 8171A clock are chugging right along in sync with the proper time. I have only looked at the digital LED output and it is within one second of my other WWVB  clocks.  Seems like magic. It came in synch about two weeks ago and stayed there. I haven't changed anything in my lab or moved the units. Antenna is still the same.      Pictures available. Doug K6JEY
_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Martin VE3OAT
2018-04-13 00:12:01 UTC
Reply
Permalink
Raw Message
Hi, Doug,
How is your 8161 doing now? Still synced properly? Should I bring my
8164 up from the basement? I was so disappointed when WWVB changed
their modulation. Thanks for any encouragement.
73,
... Martin VE3OAT
Post by Doug Millar via time-nuts
Hi, My Spectracom 8161 comparator and 8171A clock are chugging
right along in sync with the proper time. I have only looked at
the digital LED output and it is within one second of my other
WWVB clocks. Seems like magic. It came in synch about two
weeks ago and stayed there. I haven't changed anything in my
lab or moved the units. Antenna is still the same.
Pictures available. Doug K6JEY
_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Tom Van Baak
2018-04-13 03:07:37 UTC
Reply
Permalink
Raw Message
I've been talking with Doug to better understand why his Spectracom WWVB receiver shows the green lock indicator. This receiver should not work given the enhanced WWVB modulation we've had since 2012. Fortunately he has chosen not to touch anything while we ponder this.

Meanwhile I pulled out some Spectracom gear (8164) and was able to repro his green lock! But the 10 MHz output is very unstable so I'm pretty sure it is not locking at all. Looking at the schematic the green indicator seems primitive. So "lock" may not really mean it has robustly locked to the carrier. More details to follow.

If any of you have Spectracom WWVB 816x or 817x receivers you might want to try them too.

/tvb

----- Original Message -----
From: "Martin VE3OAT" <***@storm.ca>
To: <time-***@febo.com>
Cc: "Doug Millar" <***@yahoo.com>
Sent: Thursday, April 12, 2018 5:12 PM
Subject: Re: [time-nuts] WWVB information
Post by Martin VE3OAT
Hi, Doug,
How is your 8161 doing now? Still synced properly? Should I bring my
8164 up from the basement? I was so disappointed when WWVB changed
their modulation. Thanks for any encouragement.
73,
... Martin VE3OAT
Post by Doug Millar via time-nuts
Hi, My Spectracom 8161 comparator and 8171A clock are chugging
right along in sync with the proper time. I have only looked at
the digital LED output and it is within one second of my other
WWVB clocks. Seems like magic. It came in synch about two
weeks ago and stayed there. I haven't changed anything in my
lab or moved the units. Antenna is still the same.
Pictures available. Doug K6JEY
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Tom Van Baak
2018-04-13 16:02:16 UTC
Reply
Permalink
Raw Message
So Doug's Spectracom WWVB receiver shows a green lock status. I didn't believe it, but he sent a photo. I then tried it here and the same thing happens to me. It's very suspicious because we know these old carrier phase WWVB receivers don't work with the enhanced WWVB broadcast format.

Instead of trusting the green light I measured the 5 MHz output of the WWVB-disciplined receiver using a hp 53132A. Here's an example of 1 second readings with no antenna (no lock):
4999931.22296 Hz
4999931.22650 Hz
4999931.22709 Hz
4999931.209453 Hz
4999931.21235 Hz
STD DEV: 0.007968 Hz

You see a free-running undisciplined OCXO. Not very accurate but very stable.

Then I connected the WWVB antenna. Within seconds the green lock light came on. The readings looked like:
4999994.676217 Hz
5000014.45065 Hz
4999966.61447 Hz
4999963.27949 Hz
4999971.40319 Hz
STD DEV: 15.853246 Hz

You see that the OCXO has been steered closer to 5 MHz, but the stability is horrible.

Lastly, just to check the system was working, I applied a 60 kHz carrier near the antenna using a hp 3325B. The readings look like:
4999999.9693 Hz
5000000.0199 Hz
5000000.0202 Hz
4999999.9693 Hz
4999999.9998 Hz
STD DEV: 0.02355 Hz

In this case very accurate and quite stable.

ADEV plot of all three runs is attached.

So my conclusion is the green lock light is false. The Spectracom really isn't locking to the carrier. It's trying hard, but the new phase encoding keeps this from happening. Someone can take a look at the block diagram or schematic and explain why the circuit gets fooled into thinking there is lock when there really isn't. Look for Spectracom 8161 or 8164 on ko4bb's manual site.

The one mystery is why this false green only started a week ago for Doug. If any of you have Spectracom WWVB receivers, fire then up and see what happens. I think I'll keep mine going for a few days or months and see if the false green ever goes out.

/tvb

Hal Murray
2018-04-13 21:26:21 UTC
Reply
Permalink
Raw Message
The month recently changed from 3 to 4. A while ago, the bottom digit of the
year changed from 8 to 7. I think the out-of-phase time is shorter for a 0
than for a 1. Would a few more 0 bits be enough to push it into sync?

Is there "goodness" parameter that you can monitor? It might be interesting
to see if that correlates with day, hour, minute encoding?
--
These are my opinions. I hate spam.



_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
paul swed
2018-04-13 22:16:45 UTC
Reply
Permalink
Raw Message
Hal when I was building de-psk-ers and such I have to say I did not see the
imbalance. It looked pretty solid in timing.
The fact that at each minute for the first number of seconds the phase is
actually fixed just before the preamble is useful.
It clears out any possible buildup if it existed.
Also unless I used a number of tricks like de-psk-rs and fixed carrier
insertion none of my spectracoms. True Times would decode time. I am east
cost US so quite far away from wwvb. I believe simple tricks by others far
closer actually do work.
Regards
Paul
WB8TSL
Post by Hal Murray
The month recently changed from 3 to 4. A while ago, the bottom digit of the
year changed from 8 to 7. I think the out-of-phase time is shorter for a 0
than for a 1. Would a few more 0 bits be enough to push it into sync?
Is there "goodness" parameter that you can monitor? It might be interesting
to see if that correlates with day, hour, minute encoding?
--
These are my opinions. I hate spam.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Loading...