Discussion:
WWVB: measuring local 60 KHz noise
(too old to reply)
Hal Murray
2018-05-05 08:08:52 UTC
Permalink
Review/background: I have an UltraLink 333 WWVB receiver. It didn't work.
Several weeks ago. a discussion here mentioned that the phone cable between
the main box and antenna needs to be straight through rather than the typical
reversed. That was my problem. With the correct cable, the meter shows
signal and bounces around such that with practice, I could probably read the
bit pattern. But it didn't lock up.

That was several weeks ago. I left it running. When I looked last night, it
had figured out that it is 2018. I wasn't watching or monitoring, so I don't
know how long it took.

I assume the problem is noise. Is there any simple way to measure the noise
around 60 KHz? How about not so simple?

Extra credit for a way that others nuts can reproduce so we can compare the
noise at my location with other locations.

Can any audio cards be pushed that high? I see sample rates of 192K, but I
don't know if that is useful.

I'd also like to measure the propagation delays on WWV so a setup for HF that
also works down to 60 KHz would be interesting.

----------

The UltraLink documentation says the display has a slot for a C or H. The C is for Colorado and the H is for Hawaii. Did WWVH have a low frequency transmitter many years ago? The NIST history of WWVH doesn't mention it.

My guess is a cut+paste from a version that listened to WWV/WWVH.
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Ulrich Rohde via time-nuts
2018-05-05 13:17:06 UTC
Permalink
 
I am trying to use the 60 KHz for synchronization of a Rb receiver. The local NJ noise and the signal in dBuV are about the same with an active antenna, electric field.  A better solution might be a ferrite selective antenna, H field , if I find one.
 
73 de N1UL 
 
 
In a message dated 5/5/2018 4:09:25 AM Eastern Standard Time, ***@megapathdsl.net writes:

 
Review/background: I have an UltraLink 333 WWVB receiver. It didn't work.
Several weeks ago. a discussion here mentioned that the phone cable between
the main box and antenna needs to be straight through rather than the typical
reversed. That was my problem. With the correct cable, the meter shows
signal and bounces around such that with practice, I could probably read the
bit pattern. But it didn't lock up.

That was several weeks ago. I left it running. When I looked last night, it
had figured out that it is 2018. I wasn't watching or monitoring, so I don't
know how long it took.

I assume the problem is noise. Is there any simple way to measure the noise
around 60 KHz? How about not so simple?

Extra credit for a way that others nuts can reproduce so we can compare the
noise at my location with other locations.

Can any audio cards be pushed that high? I see sample rates of 192K, but I
don't know if that is useful.

I'd also like to measure the propagation delays on WWV so a setup for HF that
also works down to 60 KHz would be interesting.

----------

The UltraLink documentation says the display has a slot for a C or H. The C is for Colorado and the H is for Hawaii. Did WWVH have a low frequency transmitter many years ago? The NIST history of WWVH doesn't mention it.

My guess is a cut+paste from a version that listened to WWV/WWVH.
--
These are my opinions. I hate spam.



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Bob kb8tq
2018-05-05 13:57:12 UTC
Permalink
Hi

Even if you get the 60 KHz process working, a $20 GPS module ( or maybe $50) will
do a much better job. That’s not saying *don’t* do the WWVB stuff. Just realize it’s
limitations. A second limitation is that the new phase modulation process makes
comparison a bit more complex.

60 KHz noise can be measured with any of a number of SDR’s that tune down there.
An RTL-SDR probably isn’t ideal, but there are a lot of sub $200 devices that will do
very well.

Once you have a tuner you need a “standard” antenna (if this is for noise). Some sort
of single turn loop is probably the best bet. Assuming the input to the SDR comes
pre-calibrated you are ready to go. If it’s not calibrated you will need to squirt a test
tone of known level in at 60 KHz to calibrate it ( likely a one time thing).

60 KHz reception is a bit iffy these days. The low cost world *loves* 60KHz as a
switcher frequency. It only takes one of them near your reception site to mess things
up. The E-field probe vs loop debate has been going on for at least a century by now.
I’d go with some sort of loop. With a proper location, either can work well.

Lots of fun ….

Bob
I am trying to use the 60 KHz for synchronization of a Rb receiver. The local NJ noise and the signal in dBuV are about the same with an active antenna, electric field. A better solution might be a ferrite selective antenna, H field , if I find one.
73 de N1UL
Review/background: I have an UltraLink 333 WWVB receiver. It didn't work.
Several weeks ago. a discussion here mentioned that the phone cable between
the main box and antenna needs to be straight through rather than the typical
reversed. That was my problem. With the correct cable, the meter shows
signal and bounces around such that with practice, I could probably read the
bit pattern. But it didn't lock up.
That was several weeks ago. I left it running. When I looked last night, it
had figured out that it is 2018. I wasn't watching or monitoring, so I don't
know how long it took.
I assume the problem is noise. Is there any simple way to measure the noise
around 60 KHz? How about not so simple?
Extra credit for a way that others nuts can reproduce so we can compare the
noise at my location with other locations.
Can any audio cards be pushed that high? I see sample rates of 192K, but I
don't know if that is useful.
I'd also like to measure the propagation delays on WWV so a setup for HF that
also works down to 60 KHz would be interesting.
----------
The UltraLink documentation says the display has a slot for a C or H. The C is for Colorado and the H is for Hawaii. Did WWVH have a low frequency transmitter many years ago? The NIST history of WWVH doesn't mention it.
My guess is a cut+paste from a version that listened to WWV/WWVH.
--
These are my opinions. I hate spam.
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Alexander Pummer
2018-05-05 19:35:47 UTC
Permalink
tuned,[ fine-tuning with vari-caps remotely] large size frame antenna 1
meter dia provides mV size 60kHz in the Livermore area in California
from the Colorado WWVB TX
73
KJ6UHN
Alex
I am trying to use the 60 KHz for synchronization of a Rb receiver. The local NJ noise and the signal in dBuV are about the same with an active antenna, electric field. A better solution might be a ferrite selective antenna, H field , if I find one.
73 de N1UL
Review/background: I have an UltraLink 333 WWVB receiver. It didn't work.
Several weeks ago. a discussion here mentioned that the phone cable between
the main box and antenna needs to be straight through rather than the typical
reversed. That was my problem. With the correct cable, the meter shows
signal and bounces around such that with practice, I could probably read the
bit pattern. But it didn't lock up.
That was several weeks ago. I left it running. When I looked last night, it
had figured out that it is 2018. I wasn't watching or monitoring, so I don't
know how long it took.
I assume the problem is noise. Is there any simple way to measure the noise
around 60 KHz? How about not so simple?
Extra credit for a way that others nuts can reproduce so we can compare the
noise at my location with other locations.
Can any audio cards be pushed that high? I see sample rates of 192K, but I
don't know if that is useful.
I'd also like to measure the propagation delays on WWV so a setup for HF that
also works down to 60 KHz would be interesting.
----------
The UltraLink documentation says the display has a slot for a C or H. The C is for Colorado and the H is for Hawaii. Did WWVH have a low frequency transmitter many years ago? The NIST history of WWVH doesn't mention it.
My guess is a cut+paste from a version that listened to WWV/WWVH.
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Dana Whitlow
2018-05-05 21:27:36 UTC
Permalink
Alex- how many turns on that loop?

Dana
Post by Alexander Pummer
tuned,[ fine-tuning with vari-caps remotely] large size frame antenna 1
meter dia provides mV size 60kHz in the Livermore area in California from
the Colorado WWVB TX
73
KJ6UHN
Alex
Post by Ulrich Rohde via time-nuts
I am trying to use the 60 KHz for synchronization of a Rb receiver. The
local NJ noise and the signal in dBuV are about the same with an active
antenna, electric field. A better solution might be a ferrite selective
antenna, H field , if I find one.
73 de N1UL
In a message dated 5/5/2018 4:09:25 AM Eastern Standard Time,
Review/background: I have an UltraLink 333 WWVB receiver. It didn't work.
Several weeks ago. a discussion here mentioned that the phone cable between
the main box and antenna needs to be straight through rather than the typical
reversed. That was my problem. With the correct cable, the meter shows
signal and bounces around such that with practice, I could probably read the
bit pattern. But it didn't lock up.
That was several weeks ago. I left it running. When I looked last night, it
had figured out that it is 2018. I wasn't watching or monitoring, so I don't
know how long it took.
I assume the problem is noise. Is there any simple way to measure the noise
around 60 KHz? How about not so simple?
Extra credit for a way that others nuts can reproduce so we can compare the
noise at my location with other locations.
Can any audio cards be pushed that high? I see sample rates of 192K, but I
don't know if that is useful.
I'd also like to measure the propagation delays on WWV so a setup for HF that
also works down to 60 KHz would be interesting.
----------
The UltraLink documentation says the display has a slot for a C or H. The
C is for Colorado and the H is for Hawaii. Did WWVH have a low frequency
transmitter many years ago? The NIST history of WWVH doesn't mention it.
My guess is a cut+paste from a version that listened to WWV/WWVH.
_______________________________________________
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ailman/listinfo/time-nuts
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Alberto di Bene
2018-05-05 21:42:49 UTC
Permalink
If you have a sound card capable of sampling at 192 kS/s, you don't need an SDR
to receive a signal at 60 kHz... just connect the output of an active antenna, like
e.g. the mini-whip, directly to the Line-In of the sound card, then use, for example,
HDSDR as software, setting the sampling frequency of the sound card to 192 kS/s,
the LO to zero, and the TUNE to 60 kHz.

I used this method in the past to successfully receive the SAQ transmission at 17.2 kHz
Look here :

http://www.sdradio.eu/SAQ_2009_12_24.html

73  Alberto  I2PHD


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Bob kb8tq
2018-05-05 22:36:56 UTC
Permalink
Hi

The sample rate on a sound card is not always a good indication of it’s
performance. Some 192 KS/s cards have cutoff’s below 50 KHz. Others
have a noise spectrum that rises quite a bit past 30 or 40 KHz.

Lots to dig into ….

Bob
Post by Alberto di Bene
If you have a sound card capable of sampling at 192 kS/s, you don't need an SDR
to receive a signal at 60 kHz... just connect the output of an active antenna, like
e.g. the mini-whip, directly to the Line-In of the sound card, then use, for example,
HDSDR as software, setting the sampling frequency of the sound card to 192 kS/s,
the LO to zero, and the TUNE to 60 kHz.
I used this method in the past to successfully receive the SAQ transmission at 17.2 kHz
http://www.sdradio.eu/SAQ_2009_12_24.html
73 Alberto I2PHD
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Charles Steinmetz
2018-05-06 04:39:00 UTC
Permalink
Post by Alberto di Bene
If you have a sound card capable of sampling at 192 kS/s, you don't need an SDR
to receive a signal at 60 kHz... just connect the output of an active antenna, like
e.g. the mini-whip, directly to the Line-In of the sound card * * *
I used this method in the past to successfully receive the SAQ transmission at 17.2 kHz
You have to be careful about this -- the vast majority of computer sound
cards are designed to handle the audio spectrum up to around 20-22kHz.
Cards that have sampling rates in excess of about 48kS per second most
often DO NOT process input signals higher than ~22kHz. The higher
sampling rate is used only for oversampling and noise shaping (look
these up if they are unfamiliar terms), and the digital signals are
noise-shaped and decimated on-card from 96kS, 192kS, 384kS, etc. down to
48kS and lower.

So, yes, a sound card designed for signals up to ~22kHz should handle
SAQ at ~17kHz, but sound cards that can digitize signals above 22kHz are
rare. Some "professional" sound cards handle signal frequencies up to
~40kHz, but very, very few handle signal frequencies higher than that.
There are also digitizers designed more for instrumentation and data
acquisition than audio that may meet your requirements.

SO: If you want to digitize frequencies > ~22kHz, read the
documentation for the cards you are considering VERY carefully. I
haven't been shopping for extended-frequency audio cards recently, so
I'm not up to date on what is available. Perhaps others will have
particular suggestions for digitizing WWVB.

Finally, be aware that sound cards use sampling clocks that are
invariably MUCH worse in terms of jitter and drift than the WWVB carrier
(even as it is received over the air), so you need to deal with that if
what you are after is a 60kHz reference that is as stable as WWVB.

Best regards,

Charles


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Alberto di Bene
2018-05-06 15:32:48 UTC
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Alberto di Bene
2018-05-06 20:53:13 UTC
Permalink
Post by Charles Steinmetz
So, yes, a sound card designed for signals up to ~22kHz should handle
SAQ at ~17kHz, but sound cards that can digitize signals above 22kHz are
rare. Some "professional" sound cards handle signal frequencies up to
~40kHz, but very, very few handle signal frequencies higher than that.
There are also digitizers designed more for instrumentation and data
acquisition than audio that may meet your requirements.
Bob and Charles,

  you are of course both quite right.
The card used for SAQ was the Delta 44 which is a semi-professional card.

For higher frequencies I have had quite good results with the E-MU 1212M, which
is a professional, mastering grade, sound card, used also in recording studios.

http://www.creative.com/emu/products/product.aspx?pid=19169

Not exactly inexpensive, but its 120dB signal-to-noise ratio cannot be overlooked.

73  Alberto  I2PHD




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ew via time-nuts
2018-05-05 13:26:37 UTC
Permalink
contact me off list I have a couple   Bert Kehren
 
In a message dated 5/5/2018 9:17:45 AM Eastern Standard Time, time-***@febo.com writes:

 
 
I am trying to use the 60 KHz for synchronization of a Rb receiver. The local NJ noise and the signal in dBuV are about the same with an active antenna, electric field.  A better solution might be a ferrite selective antenna, H field , if I find one.
 
73 de N1UL 
 
 
In a message dated 5/5/2018 4:09:25 AM Eastern Standard Time, ***@megapathdsl.net writes:

 
Review/background: I have an UltraLink 333 WWVB receiver. It didn't work.
Several weeks ago. a discussion here mentioned that the phone cable between
the main box and antenna needs to be straight through rather than the typical
reversed. That was my problem. With the correct cable, the meter shows
signal and bounces around such that with practice, I could probably read the
bit pattern. But it didn't lock up.

That was several weeks ago. I left it running. When I looked last night, it
had figured out that it is 2018. I wasn't watching or monitoring, so I don't
know how long it took.

I assume the problem is noise. Is there any simple way to measure the noise
around 60 KHz? How about not so simple?

Extra credit for a way that others nuts can reproduce so we can compare the
noise at my location with other locations.

Can any audio cards be pushed that high? I see sample rates of 192K, but I
don't know if that is useful.

I'd also like to measure the propagation delays on WWV so a setup for HF that
also works down to 60 KHz would be interesting.

----------

The UltraLink documentation says the display has a slot for a C or H. The C is for Colorado and the H is for Hawaii. Did WWVH have a low frequency transmitter many years ago? The NIST history of WWVH doesn't mention it.

My guess is a cut+paste from a version that listened to WWV/WWVH.
--
These are my opinions. I hate spam.



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Dana Whitlow
2018-05-05 09:50:17 UTC
Permalink
Hal,

Some SDRs can tune that low and should provide a means to determine
if noise is really the problem as well as give some clues as to the
character
of said noise. But they are much less likely to help with delay
determination,
unless you can figure out a practical way to ascertain the latency in both
the
SDR's HW and its SW. The latter component will also vary considerable
depending on what computer you are using with the SDR, as well as with
random variations due to the vagrancy of typical operating systems.

I recently did a crude delay estimation for WWV (not WWVB) using my
Sony ICF-2010 receiver, a 2-channel DSO, and an Adafruit "Ultimate GPS"
module's PPS output. The combined (receiver + propagation) delay was
very close to 5 msec in Kerrville, TX. The precision was mostly limited by
my inability to decide precisely where each WWV tick started on the 'scope's
display due to distortion arising from multipath and the receiver's
filters.
The actual received waveform varied considerably from second to second.

Dana
Post by Hal Murray
Review/background: I have an UltraLink 333 WWVB receiver. It didn't work.
Several weeks ago. a discussion here mentioned that the phone cable between
the main box and antenna needs to be straight through rather than the typical
reversed. That was my problem. With the correct cable, the meter shows
signal and bounces around such that with practice, I could probably read the
bit pattern. But it didn't lock up.
That was several weeks ago. I left it running. When I looked last night, it
had figured out that it is 2018. I wasn't watching or monitoring, so I don't
know how long it took.
I assume the problem is noise. Is there any simple way to measure the noise
around 60 KHz? How about not so simple?
Extra credit for a way that others nuts can reproduce so we can compare the
noise at my location with other locations.
Can any audio cards be pushed that high? I see sample rates of 192K, but I
don't know if that is useful.
I'd also like to measure the propagation delays on WWV so a setup for HF that
also works down to 60 KHz would be interesting.
----------
The UltraLink documentation says the display has a slot for a C or H. The
C is for Colorado and the H is for Hawaii. Did WWVH have a low frequency
transmitter many years ago? The NIST history of WWVH doesn't mention it.
My guess is a cut+paste from a version that listened to WWV/WWVH.
--
These are my opinions. I hate spam.
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mailman/listinfo/time-nuts
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Bob kb8tq
2018-05-05 15:49:10 UTC
Permalink
Hi

If you want delay ( hardware delay and not propagation), calibrating a SDR should not
be to nutty. Some boards ( the Lime SDR comes to mind) will generate a signal as well
as receive one. That could be piped into a scope to make the measurement fairly
easy. Once you know what is going into the receiver and what is coming out, it’s just
twiddling the knobs ….

Bob
Post by Dana Whitlow
Hal,
Some SDRs can tune that low and should provide a means to determine
if noise is really the problem as well as give some clues as to the
character
of said noise. But they are much less likely to help with delay
determination,
unless you can figure out a practical way to ascertain the latency in both
the
SDR's HW and its SW. The latter component will also vary considerable
depending on what computer you are using with the SDR, as well as with
random variations due to the vagrancy of typical operating systems.
I recently did a crude delay estimation for WWV (not WWVB) using my
Sony ICF-2010 receiver, a 2-channel DSO, and an Adafruit "Ultimate GPS"
module's PPS output. The combined (receiver + propagation) delay was
very close to 5 msec in Kerrville, TX. The precision was mostly limited by
my inability to decide precisely where each WWV tick started on the 'scope's
display due to distortion arising from multipath and the receiver's
filters.
The actual received waveform varied considerably from second to second.
Dana
Post by Hal Murray
Review/background: I have an UltraLink 333 WWVB receiver. It didn't work.
Several weeks ago. a discussion here mentioned that the phone cable between
the main box and antenna needs to be straight through rather than the typical
reversed. That was my problem. With the correct cable, the meter shows
signal and bounces around such that with practice, I could probably read the
bit pattern. But it didn't lock up.
That was several weeks ago. I left it running. When I looked last night, it
had figured out that it is 2018. I wasn't watching or monitoring, so I don't
know how long it took.
I assume the problem is noise. Is there any simple way to measure the noise
around 60 KHz? How about not so simple?
Extra credit for a way that others nuts can reproduce so we can compare the
noise at my location with other locations.
Can any audio cards be pushed that high? I see sample rates of 192K, but I
don't know if that is useful.
I'd also like to measure the propagation delays on WWV so a setup for HF that
also works down to 60 KHz would be interesting.
----------
The UltraLink documentation says the display has a slot for a C or H. The
C is for Colorado and the H is for Hawaii. Did WWVH have a low frequency
transmitter many years ago? The NIST history of WWVH doesn't mention it.
My guess is a cut+paste from a version that listened to WWV/WWVH.
--
These are my opinions. I hate spam.
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mailman/listinfo/time-nuts
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Mark Sims
2018-05-05 15:04:44 UTC
Permalink
Although it does not measure propagation delays, Lady Heather can now estimate propagation delays. You can enter the lat/lon/alt of the station or specify the station name. You can enter the ionosphere height, or Heather will estimate it depending upon the month.

-------------------
Post by Hal Murray
I'd also like to measure the propagation delays on WWV so a setup for HF that
also works down to 60 KHz would be interesting.
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Bruce Hunter via time-nuts
2018-05-05 17:05:49 UTC
Permalink
I have found the proximity of my home computer has kept a bedroom projection clock from locking to WWVB. Apparently the noise radiation from the computer effectively jams the 60 kHz signal.

By setting the clock out on a deck about 30 feet further away from the computer, the clock locks up every time in about five minutes. I take the batteries out to reboot the clock. Otherwise it waits until after midnight to began searching for the WWVB signal. Presumably the designers felt 60 kHz noise levels were lower at that time of night.

Bruce, KG6OJI
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Bruce Hunter via time-nuts
2018-05-05 17:05:49 UTC
Permalink
I have found the proximity of my home computer has kept a bedroom projection clock from locking to WWVB. Apparently the noise radiation from the computer effectively jams the 60 kHz signal.

By setting the clock out on a deck about 30 feet further away from the computer, the clock locks up every time in about five minutes. I take the batteries out to reboot the clock. Otherwise it waits until after midnight to began searching for the WWVB signal. Presumably the designers felt 60 kHz noise levels were lower at that time of night.

Bruce, KG6OJI
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Charles Steinmetz
2018-05-06 17:08:57 UTC
Permalink
Post by Hal Murray
I assume the problem is noise. Is there any simple way to measure the noise
around 60 KHz? How about not so simple?
Extra credit for a way that others nuts can reproduce so we can compare the
noise at my location with other locations.
For any location near a city, the noise level (QRM and QRN -- mostly the
former unless there is storm activity within a few hundred km) is
shockingly high. High enough to be clearly seen and measured with a
good spectrum analyzer. So the *simplest* way (but not necessarily the
cheapest, depending on what is in your lab already) is to use a good
spec an with noise integration over the band of interest (e.g., HP 3585A
or B). You get noise density readings in volts per root Hz. Divide by
the antenna length and you have volts per root Hz per meter.

Lacking a suitable spec an, any receiver with a reasonably narrow rx B/W
and a calibrated, input-referred detector can be used. Wave analyzers
(frequency-selectable voltmeters, e.g., HP 3586) are good candidates, as
are some commercial receivers with calibrated "S" meters (e.g., Ten-Tec
RX340). It would also be pretty easy to design a simple "sniffer"-type
receiver (input op-amp, active filter, logarithmic detector feeding a
standard 1mA meter movement) that could be calibrated by design from
first principles and that everyone interested could build for, perhaps,
$25-30.

In the suburbs of a fairly large US city with aerial electric service, I
generally see noise densities measured in tens to hundreds of uV per
root Hz per meter below 100kHz. In other, similar locations I have seen
as much as hundreds of mV or more per root Hz per meter. It depends on
local factors (whether the electric service is buried or aerial, how
well the power utility maintains its equipment, how far away the nearest
industrial neighborhood is, how far between dwellings, how much noisy
technology the neighbors use, etc, etc.).

In order to compare with others, everyone needs to use the same antenna.
There are lots of possibilities, but for the sake of universality I
recommend a 1m vertical whip. Everyone can make one of those.

Note that this sort of antenna is NOT the best type to minimize received
noise and maximize received S/N ratio. For that, you generally want a
balanced, shielded loop.

Best regards,

Charles


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Bob kb8tq
2018-05-06 18:28:31 UTC
Permalink
Hi

First off, I don’t think there *is* an ideal antenna that “just works”. Maybe a proper set of EMAG
probes that come with calibration sheets come close. For a home built this or that …. there are
a lot of variables.

First up is very much part of receiving WWVB in the first place. Coax to an antenna can have currents
on the outer shield. If they meet up with everything else at the antenna, you are not just measuring
the antenna output. Equally, if reception is the goal, you may have a ton of noise that you didn’t really
want to have. Of course, the coax might act as a really good antenna …. who knows.

Something like a 6” diameter single turn loop with a good choke at the antenna end of the coax would
be my first choice. Not super sensitive. It’s not the ideal reception antenna. For chasing down noise, smaller
is often better. As mentioned earlier we are after stuff that may be in the millivolts per meter range.

Classic data:

ftp://ftp.ngdc.noaa.gov/ionosonde/documentation/CCIR%20-%20Characteristics%20and%20Applications%20of%20Atmospheric%20Radio%20Noise%20Data.PDF <ftp://ftp.ngdc.noaa.gov/ionosonde/documentation/CCIR%20-%20Characteristics%20and%20Applications%20of%20Atmospheric%20Radio%20Noise%20Data.PDF>

puts the atmospheric noise at 120 db above KTB in the vicinity of 60 KHz. That would put it in the roughly
-54 dbm / Hz range. If your spectrum analyzer has a 1KHz bandwidth, that’s 30 db relative to 1 Hz. Your
SA should read about -24 dbm ( with an efficient antenna). Coming up with a 1/4 wave vertical at 60 KHz
may make getting those numbers a bit difficult :). Bottom line is still — there’s a lot of noise at 60 KHz. Also
note that the report came out *long* before the modern era of 60 KHz switchers …..

Bob
Post by Hal Murray
I assume the problem is noise. Is there any simple way to measure the noise
around 60 KHz? How about not so simple?
Extra credit for a way that others nuts can reproduce so we can compare the
noise at my location with other locations.
For any location near a city, the noise level (QRM and QRN -- mostly the former unless there is storm activity within a few hundred km) is shockingly high. High enough to be clearly seen and measured with a good spectrum analyzer. So the *simplest* way (but not necessarily the cheapest, depending on what is in your lab already) is to use a good spec an with noise integration over the band of interest (e.g., HP 3585A or B). You get noise density readings in volts per root Hz. Divide by the antenna length and you have volts per root Hz per meter.
Lacking a suitable spec an, any receiver with a reasonably narrow rx B/W and a calibrated, input-referred detector can be used. Wave analyzers (frequency-selectable voltmeters, e.g., HP 3586) are good candidates, as are some commercial receivers with calibrated "S" meters (e.g., Ten-Tec RX340). It would also be pretty easy to design a simple "sniffer"-type receiver (input op-amp, active filter, logarithmic detector feeding a standard 1mA meter movement) that could be calibrated by design from first principles and that everyone interested could build for, perhaps, $25-30.
In the suburbs of a fairly large US city with aerial electric service, I generally see noise densities measured in tens to hundreds of uV per root Hz per meter below 100kHz. In other, similar locations I have seen as much as hundreds of mV or more per root Hz per meter. It depends on local factors (whether the electric service is buried or aerial, how well the power utility maintains its equipment, how far away the nearest industrial neighborhood is, how far between dwellings, how much noisy technology the neighbors use, etc, etc.).
In order to compare with others, everyone needs to use the same antenna. There are lots of possibilities, but for the sake of universality I recommend a 1m vertical whip. Everyone can make one of those.
Note that this sort of antenna is NOT the best type to minimize received noise and maximize received S/N ratio. For that, you generally want a balanced, shielded loop.
Best regards,
Charles
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John Ackermann N8UR
2018-05-06 20:07:22 UTC
Permalink
Long ago I did some WWVB signal-to-noise measurements with an HP 3586C selective voltmeter (commonly used by the FMT-nuts).  I measured the signal power at 60.0 kHz with 20 Hz bandwidth.  Then I measured the power a small offset plus and minus  (100 Hz?  I don't recall), and took the mean of the two to get the noise power.  I used a voltage-probe antenna. 

Since all readings were taken with the same bandwidth I didn't bother normalizing to 1 Hz, and just used the dBm difference between the signal and mean noise as the result.  I took measurements every 5 minutes or so to capture the 24 hour cycle of SNR.

John
Post by Hal Murray
Post by Hal Murray
I assume the problem is noise. Is there any simple way to measure
the noise
Post by Hal Murray
around 60 KHz? How about not so simple?
Extra credit for a way that others nuts can reproduce so we can
compare the
Post by Hal Murray
noise at my location with other locations.
For any location near a city, the noise level (QRM and QRN -- mostly the
former unless there is storm activity within a few hundred km) is
shockingly high. High enough to be clearly seen and measured with a
good spectrum analyzer. So the *simplest* way (but not necessarily the
cheapest, depending on what is in your lab already) is to use a good
spec an with noise integration over the band of interest (e.g., HP 3585A
or B). You get noise density readings in volts per root Hz. Divide by
the antenna length and you have volts per root Hz per meter.
Lacking a suitable spec an, any receiver with a reasonably narrow rx B/W
and a calibrated, input-referred detector can be used. Wave analyzers
(frequency-selectable voltmeters, e.g., HP 3586) are good candidates, as
are some commercial receivers with calibrated "S" meters (e.g., Ten-Tec
RX340). It would also be pretty easy to design a simple "sniffer"-type
receiver (input op-amp, active filter, logarithmic detector feeding a
standard 1mA meter movement) that could be calibrated by design from
first principles and that everyone interested could build for, perhaps,
$25-30.
In the suburbs of a fairly large US city with aerial electric service, I
generally see noise densities measured in tens to hundreds of uV per
root Hz per meter below 100kHz. In other, similar locations I have seen
as much as hundreds of mV or more per root Hz per meter. It depends on
local factors (whether the electric service is buried or aerial, how
well the power utility maintains its equipment, how far away the nearest
industrial neighborhood is, how far between dwellings, how much noisy
technology the neighbors use, etc, etc.).
In order to compare with others, everyone needs to use the same
antenna.
There are lots of possibilities, but for the sake of universality I
recommend a 1m vertical whip. Everyone can make one of those.
Note that this sort of antenna is NOT the best type to minimize
received
noise and maximize received S/N ratio. For that, you generally want a
balanced, shielded loop.
Best regards,
Charles
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https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Brooke Clarke
2018-05-06 18:16:21 UTC
Permalink
Hi Hal:

You might want to check the orientation and location of the antenna before digging into more technical areas.
It's been my experience there's a lot of AC mains conducted noise at 60 kHz.
http://www.prc68.com/I/LF-Ant.shtml#Noise
http://www.prc68.com/I/Spec_0002.shtml - 0 to 200 kHz spectrum plot (PS when LORAN-C was on the air)
Another source of noise is an LCD screen.
Note Wellenbrook Communications suggests placing their loop antenna 100 feet from your house.

The loopstick antenna in the UltraLink is a single ferrite rod with nulls off the ends, so orientation is important, not
so much that you have to point the maximum at WWVB, but that you don't want to point the null at WWVB.  I'm in
California and have had to relocate WWVB clocks on walls 90 degrees to where I'd rather have them because of this.
http://www.prc68.com/I/Loop.shtml
http://www.prc68.com/I/Shadow-Clock.shtml#WT5360U
--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html

-------- Original Message --------
Post by Hal Murray
Review/background: I have an UltraLink 333 WWVB receiver. It didn't work.
Several weeks ago. a discussion here mentioned that the phone cable between
the main box and antenna needs to be straight through rather than the typical
reversed. That was my problem. With the correct cable, the meter shows
signal and bounces around such that with practice, I could probably read the
bit pattern. But it didn't lock up.
That was several weeks ago. I left it running. When I looked last night, it
had figured out that it is 2018. I wasn't watching or monitoring, so I don't
know how long it took.
I assume the problem is noise. Is there any simple way to measure the noise
around 60 KHz? How about not so simple?
Extra credit for a way that others nuts can reproduce so we can compare the
noise at my location with other locations.
Can any audio cards be pushed that high? I see sample rates of 192K, but I
don't know if that is useful.
I'd also like to measure the propagation delays on WWV so a setup for HF that
also works down to 60 KHz would be interesting.
----------
The UltraLink documentation says the display has a slot for a C or H. The C is for Colorado and the H is for Hawaii. Did WWVH have a low frequency transmitter many years ago? The NIST history of WWVH doesn't mention it.
My guess is a cut+paste from a version that listened to WWV/WWVH.
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