WWVB brain teaser

[W1RKW]

I have a battery operated "atomic" clock here in the shack. some time last year the clock stopped syncing with the WWVB time signal. Nothing was changed in the shack/house that could cause interference.  Just one day it just mysteriously stopped syncing.  No matter what I did with the clock (moving it around) improved the situation. It would receive WWVB but it just would not sync.
 
Last weeks winter storm knocked out power here for 39hours. With the power out, the clock synced with WWVB immediately. So it seems I had an interference issue all along and maybe not necessarily in my shack but maybe near by. Now with power restored, the clock continues to sync as it should.  The question is why? I never touched it before or after the power outage so I haven't a clue why it is working now. Any theories?

[n9rkm]

Try walking around the house with an AM radio tuned to 600KHz to find any noise from any cheap chargers.

Good luck.

[Pete, WA2CWA]

Try walking around the house with an AM radio tuned to 600KHz to find any noise from any cheap chargers.

Good luck.

They transmit on 60 KHz.

[AJ1G]

My theory is that the source of the noise that was interfering with the
60 kHz WWVB time code signal was either somehow corrected in the process of restoring the damaged power  line or it was a from a source that shut down on the loss of power and did not automatically restart when power came back on.  It may come
back if someone notices it’s off and turns it back on again.

Good luck, hope things stay quiet!

73 de Chris AJ1G

[W1RKW]

Chris,  I am thinking the same thing but taking it one step further after reading up on how the WWVB time code works.  https://en.wikipedia.org/wiki/WWVB
My thinking is this; even though the clock indicated it could receive the signal, in this case the carrier signal, the clock could not "hear" the data bit signal(s). A data bit is made by reducing the carrier by 17dB for a very short period of time. So I'm thinking I had a noise level that was in between the carrier level and the data bit level or right on the edge of the data bit signal level.  

Only time will tell if the noise level comes back up and then finding it

[W1RKW]

Chris,
Lost the ability to sync yesterday. it was a good run.  Have no idea what changed.

[AJ1G]

Have you tried changing the location and or orientation of the clock? If you are dealing with a marginal signal level maybe another quieter location or changing the position of the clock (specifically the assumed loop antenna inside) may help.

WWVB signal at 60 kHz is very high SNR at night on a small east-west selectable Beverage here on my Wandell & Goltermann AT-611 selective level meter and RAK
Navy VLF/LF receiver.  Also usually detectable at lower SNR the rest of the day.

[W1RKW]

I have tried moving it around but haven't really put much effort to finding a good spot. What i would like to do is find the noise source. just not sure how to go about receiving 60kHz.

[AJ1G]

You could use a local SDR if you have one at your home QTH.  But be advised some perform better at VLF than others.  I’m using a NooElec 8bit 25 MHz + base band RTL SDR dongle with one of their 5 kHz-25MHz upconverters.  It has a fairly high self noise floor below 100 kHz but I’ve been able to improve it a bit with an instrument type wideband audio preamp as a front end, also using a lot of low pass filtering and a NooElec BCB stop band pre-filter to keep BCB related cross mod crud out of the signal path, along with a tunable and we’ll shielded very high Q parallel LC wave trap in the signal path to keep the local 1230 kHz WBCQ 1KW 24/7 about a mile away out of the front end.

Good VLF performance with SDRs is achievable, as evidenced by a large number of web accessible on-line SDRs.

[W1RKW]

the closest thiing I have to an SDR is an online SDR and most of the close ones seem to only cover HF.