[ntp:questions] Re: WWVB 60kHz Receiver

David L. Mills mills at udel.edu
Mon Apr 17 03:12:04 UTC 2006


John,

Get a couple of nice big ferrite cores and take a couple of turns with 
your downlead. Also, I hope you are using the LORAN loop; the whip is 
far inferior. My Austron receivers have both failed and my homebrew 
LORAN works onlu pm ISA bus.

In the twenty years I have been here the RFI/EMI all over the LF, MF and 
HF bands has grown steadily worse. The W3UD ham radio club HF gear is 
essentially unusable.

Dave, w3hcf

John Ackermann N8UR wrote:

> Hi Dave --
> 
> We've chatted about your WWVB problems in the past, and you seem to have
> a real collection of noisemakers that cause problems.  On the other
> hand, I get really good reception here in Ohio.  I'm using the
> Spectracom ferrite antenna (with internal preamp) up on the roof of my
> house, and don't have any major spark generators nearby.  I do, however,
> have challenges of my own with a few AM broadcasters that put in very
> strong signals.  The BCB power coming down the coax of my wideband LF
> antenna is so great that my LORAN receiver shows a diurnal phase shift
> when the broadcaster changes antenna pattern at sunrise and sunset.
> 
> I get very good signal strength, and the 8170 loses lock maybe once
> every 10 days; I've never actually seen the "lock" LED go off when I was
> there.
> 
> I just looked at the NIST WWVB page, and it looks like the experiment
> they were doing with the modulation depth has become permanent -- the
> advertised power drop is now 17dB instead of the 10dB it used to be.  I
> wonder if that might have a negative effect on some users, particularly
> if they are competing with a lot of local noise.
> 
> I guess from Dave's, and my, experience you can draw the conclusion that
> WWVB reception quality may be very dependent on the local environment.
> 
> By the way -- despite my fondness for LF, I'll readily acknowledge that
> GPS is certainly a better time source in a whole bunch of ways, as long
> as you can see the sky.
> 
> John
> ----
> David L. Mills said the following on 04/15/2006 11:31 PM:
> 
>>John, et al,
>>
>>You are not going to like this.
>>
>>I;ve been running several WWVB clocks since 1981 using Spectracom 8170
>>and Netclock/2 receivers with the NTP WWVB driver. NIST Time and
>>Frequency Services, NIST Special Publication 462 (Revised 1990), claims
>>nominal timecode accuracy of 100 microseconds, and that's what I got in
>>the beginning.
>>
>>The WWVB signal has become degraded in recent years and now all WWVB
>>receivers here have been retired. Here in Delaware we are on the 100
>>microvolt per meter contour (before the WWVB transmitter upgrade) and
>>normally this would be sufficient for good accuracy. However, at least
>>here in Newark, there is another strong signal on 60 kHz that interferes
>>with WWVB. I chased this down to power-line conducted EMI and found the
>>interferiing signal was well above the noise several miles from campus.
>>It's not clear where it originates, but the prime suspect is a power
>>inverter for an arc welder at the Chrysler plant in town.
>>
>>This was bad enough, but then we started installing banks of UPS units
>>in the machine room and they scream like banshees on 60 kHz, even with
>>the antenna on the roof of an outbuilding. The result was total failure
>>of all our WWVB radios, at least on campus.
>>
>>Until recently I was getting good results at home, but now I see the
>>signal has failed there as well, probably due to increased crud at 60
>>kHz due some incidental radiator. I conclude WWVB is no longer useful
>>here and I suspect in any machine room, unless the antenna is far away
>>from the UPSes and with suitable ferrite decoupling.
>>
>>A solution that would probably work for business is to locate the
>>antenna and radio in a doghouse on the roof and run serial cable to the
>>machine room. Lemme tell you how hard that is with a plastic sheet roof
>>and a landlord that believes rooftop space rental for tenant machinery
>>is a significant revenue stream.
>>
>>Dave
> 
> 
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