Receiving WWVB
 

I've been thinking about building a WWVB (time code on 60kHz) receiver, and
wanted to get some suggestions for the architecture. Poking around the web
some, I did find one receiver where the guy built a synchronous detector
using a PLL and VCXO to phase-lock to the 60kHz carrier. Nice idea --
especially since he wanted the 60kHz carrier as a synchronization signal.
However, I just want the time data... so... wouldn't it be easier to build a
mixer at, e.g., 59kHz and then use an envelope detector to get a loud/quiet
audible (1kHz) tone (WWVB reduces power by 10dB to signify 0 bits in its
time code)? It seems to me that this approach avoids the need for the PLL
and VCXO, which is a nice 'reduction' in complexity. Also, since I'll have
a microcontroller around to decode the time code anyway, it can easily
generate the 59kHz signal.

Thanks,
---Joel Kolstad

Joel Kolstad wrote:

I've been thinking about building a WWVB (time code on 60kHz) receiver, and
wanted to get some suggestions for the architecture. Poking around the web
some, I did find one receiver where the guy built a synchronous detector
using a PLL and VCXO to phase-lock to the 60kHz carrier. Nice idea --
especially since he wanted the 60kHz carrier as a synchronization signal.
However, I just want the time data... so... wouldn't it be easier to build a
mixer at, e.g., 59kHz and then use an envelope detector to get a loud/quiet
audible (1kHz) tone (WWVB reduces power by 10dB to signify 0 bits in its
time code)? It seems to me that this approach avoids the need for the PLL
and VCXO, which is a nice 'reduction' in complexity. Also, since I'll have
a microcontroller around to decode the time code anyway, it can easily
generate the 59kHz signal.

Thanks,
---Joel Kolstad

I think you will need a receiver with a narrow band pass. The phase locked
scheme can help you get a very narrow band pass.

Another arrangement is use the 1 Khz as you planned and use a FFT program to
get the signal out of the noise..

And maybe, at your location, the signal is strong enough that my concerns
do not apply.

Bill K7NOM

Joel Kolstad wrote:

I've been thinking about building a WWVB (time code on 60kHz) receiver, and
wanted to get some suggestions for the architecture. Poking around the web
some, I did find one receiver where the guy built a synchronous detector
using a PLL and VCXO to phase-lock to the 60kHz carrier. Nice idea --
especially since he wanted the 60kHz carrier as a synchronization signal.
However, I just want the time data... so... wouldn't it be easier to build a
mixer at, e.g., 59kHz and then use an envelope detector to get a loud/quiet
audible (1kHz) tone (WWVB reduces power by 10dB to signify 0 bits in its
time code)? It seems to me that this approach avoids the need for the PLL
and VCXO, which is a nice 'reduction' in complexity. Also, since I'll have
a microcontroller around to decode the time code anyway, it can easily
generate the 59kHz signal.

Thanks,
---Joel Kolstad

I think you will need a receiver with a narrow band pass. The phase locked
scheme can help you get a very narrow band pass.

Another arrangement is use the 1 Khz as you planned and use a FFT program to
get the signal out of the noise..

And maybe, at your location, the signal is strong enough that my concerns
do not apply.

Bill K7NOM

I played with that many, many moons ago. The bugaboo is local noise --
QRM from all kinds of devices running from mains power, switching,
arcing, and sparking. The noise was lower late at night when more
gadgets were off, which I'm sure is why the automatic clocks you can get
now do their synchronizing late at night. So I suggest looking at each
architechture for its noise immunity and how it responds when it does
get a burst of noise. Absolute minimum bandwidth is an advantage from a
noise standpoint, as long as it's not so narrow that it rings for too
long when hit with an impulse. A PLL with long loop time constant might
be a good idea, since it should maintain synchronization through a noise
burst. Other than those generalities, I don't have much to offer. I
built up a simple receiver long ago that allowed me to see the binary
code on a scope, but only late at night. I never pursued perfecting it
to the point where it would be reliable. WWVB increased its power
between then and now, but it's probably still not a piece of cake.

Roy Lewallen, W7EL

Joel Kolstad wrote:
I've been thinking about building a WWVB (time code on 60kHz) receiver, and
wanted to get some suggestions for the architecture. Poking around the web
some, I did find one receiver where the guy built a synchronous detector
using a PLL and VCXO to phase-lock to the 60kHz carrier. Nice idea --
especially since he wanted the 60kHz carrier as a synchronization signal.
However, I just want the time data... so... wouldn't it be easier to build a
mixer at, e.g., 59kHz and then use an envelope detector to get a loud/quiet
audible (1kHz) tone (WWVB reduces power by 10dB to signify 0 bits in its
time code)? It seems to me that this approach avoids the need for the PLL
and VCXO, which is a nice 'reduction' in complexity. Also, since I'll have
a microcontroller around to decode the time code anyway, it can easily
generate the 59kHz signal.

Thanks,
---Joel Kolstad

I played with that many, many moons ago. The bugaboo is local noise --
QRM from all kinds of devices running from mains power, switching,
arcing, and sparking. The noise was lower late at night when more
gadgets were off, which I'm sure is why the automatic clocks you can get
now do their synchronizing late at night. So I suggest looking at each
architechture for its noise immunity and how it responds when it does
get a burst of noise. Absolute minimum bandwidth is an advantage from a
noise standpoint, as long as it's not so narrow that it rings for too
long when hit with an impulse. A PLL with long loop time constant might
be a good idea, since it should maintain synchronization through a noise
burst. Other than those generalities, I don't have much to offer. I
built up a simple receiver long ago that allowed me to see the binary
code on a scope, but only late at night. I never pursued perfecting it
to the point where it would be reliable. WWVB increased its power
between then and now, but it's probably still not a piece of cake.

Roy Lewallen, W7EL

Joel Kolstad wrote:
I've been thinking about building a WWVB (time code on 60kHz) receiver, and
wanted to get some suggestions for the architecture. Poking around the web
some, I did find one receiver where the guy built a synchronous detector
using a PLL and VCXO to phase-lock to the 60kHz carrier. Nice idea --
especially since he wanted the 60kHz carrier as a synchronization signal.
However, I just want the time data... so... wouldn't it be easier to build a
mixer at, e.g., 59kHz and then use an envelope detector to get a loud/quiet
audible (1kHz) tone (WWVB reduces power by 10dB to signify 0 bits in its
time code)? It seems to me that this approach avoids the need for the PLL
and VCXO, which is a nice 'reduction' in complexity. Also, since I'll have
a microcontroller around to decode the time code anyway, it can easily
generate the 59kHz signal.

Thanks,
---Joel Kolstad

Roy Lewallen wrote:

I played with that many, many moons ago. The bugaboo is local noise --
QRM from all kinds of devices running from mains power, switching,
arcing, and sparking. The noise was lower late at night when more
gadgets were off, which I'm sure is why the automatic clocks you can get
now do their synchronizing late at night. So I suggest looking at each
architechture for its noise immunity and how it responds when it does
get a burst of noise. Absolute minimum bandwidth is an advantage from a
noise standpoint, as long as it's not so narrow that it rings for too
long when hit with an impulse. A PLL with long loop time constant might
be a good idea, since it should maintain synchronization through a noise
burst. Other than those generalities, I don't have much to offer. I
built up a simple receiver long ago that allowed me to see the binary
code on a scope, but only late at night. I never pursued perfecting it
to the point where it would be reliable. WWVB increased its power
between then and now, but it's probably still not a piece of cake.

Roy Lewallen, W7EL

Joel Kolstad wrote:
I've been thinking about building a WWVB (time code on 60kHz) receiver, and
wanted to get some suggestions for the architecture. Poking around the web
some, I did find one receiver where the guy built a synchronous detector
using a PLL and VCXO to phase-lock to the 60kHz carrier. Nice idea --
especially since he wanted the 60kHz carrier as a synchronization signal.
However, I just want the time data... so... wouldn't it be easier to build a
mixer at, e.g., 59kHz and then use an envelope detector to get a loud/quiet
audible (1kHz) tone (WWVB reduces power by 10dB to signify 0 bits in its
time code)? It seems to me that this approach avoids the need for the PLL
and VCXO, which is a nice 'reduction' in complexity. Also, since I'll have
a microcontroller around to decode the time code anyway, it can easily
generate the 59kHz signal.

Thanks,
---Joel Kolstad



I get a good signal into central Florida these days. I could barely
pick them up before they replaced their antennas and upgraded the
transmitters. I could pick up the harmonics of the horizontal sweep of a
TV set over a half mile away, but WWVB was so weak it was wiped out by
power line noise and other VLF noise. Temic makes a single chip
reciever/decoder, but I don't know if it is available in small
quantities. I have the data sheets, but I have to look for them.
--


Michael A. Terrell
Central Florida

Roy Lewallen wrote:

I played with that many, many moons ago. The bugaboo is local noise --
QRM from all kinds of devices running from mains power, switching,
arcing, and sparking. The noise was lower late at night when more
gadgets were off, which I'm sure is why the automatic clocks you can get
now do their synchronizing late at night. So I suggest looking at each
architechture for its noise immunity and how it responds when it does
get a burst of noise. Absolute minimum bandwidth is an advantage from a
noise standpoint, as long as it's not so narrow that it rings for too
long when hit with an impulse. A PLL with long loop time constant might
be a good idea, since it should maintain synchronization through a noise
burst. Other than those generalities, I don't have much to offer. I
built up a simple receiver long ago that allowed me to see the binary
code on a scope, but only late at night. I never pursued perfecting it
to the point where it would be reliable. WWVB increased its power
between then and now, but it's probably still not a piece of cake.

Roy Lewallen, W7EL

Joel Kolstad wrote:
I've been thinking about building a WWVB (time code on 60kHz) receiver, and
wanted to get some suggestions for the architecture. Poking around the web
some, I did find one receiver where the guy built a synchronous detector
using a PLL and VCXO to phase-lock to the 60kHz carrier. Nice idea --
especially since he wanted the 60kHz carrier as a synchronization signal.
However, I just want the time data... so... wouldn't it be easier to build a
mixer at, e.g., 59kHz and then use an envelope detector to get a loud/quiet
audible (1kHz) tone (WWVB reduces power by 10dB to signify 0 bits in its
time code)? It seems to me that this approach avoids the need for the PLL
and VCXO, which is a nice 'reduction' in complexity. Also, since I'll have
a microcontroller around to decode the time code anyway, it can easily
generate the 59kHz signal.

Thanks,
---Joel Kolstad



I get a good signal into central Florida these days. I could barely
pick them up before they replaced their antennas and upgraded the
transmitters. I could pick up the harmonics of the horizontal sweep of a
TV set over a half mile away, but WWVB was so weak it was wiped out by
power line noise and other VLF noise. Temic makes a single chip
reciever/decoder, but I don't know if it is available in small
quantities. I have the data sheets, but I have to look for them.
--


Michael A. Terrell
Central Florida

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"Roy" =3D=3D Roy Lewallen writes:

Roy The noise was lower late at night when more gadgets were off,
Roy which I'm sure is why the automatic clocks you can get now do
Roy their synchronizing late at night.

I thought the reason they sync'ed at night was because of propagation.

Interesting.

Jack.
=2D --=20
Jack Twilley
jmt at twilley dot org
http colon slash slash www dot twilley dot org slash tilde jmt slash
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"Roy" =3D=3D Roy Lewallen writes:

Roy The noise was lower late at night when more gadgets were off,
Roy which I'm sure is why the automatic clocks you can get now do
Roy their synchronizing late at night.

I thought the reason they sync'ed at night was because of propagation.

Interesting.

Jack.
=2D --=20
Jack Twilley
jmt at twilley dot org
http colon slash slash www dot twilley dot org slash tilde jmt slash
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=3DLHM4
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Roy Lewallen wrote:

I played with that many, many moons ago. The bugaboo is local noise --
QRM from all kinds of devices running from mains power, switching,
arcing, and sparking. The noise was lower late at night when more
gadgets were off, which I'm sure is why the automatic clocks you can get
now do their synchronizing late at night. So I suggest looking at each
architechture for its noise immunity and how it responds when it does
get a burst of noise. Absolute minimum bandwidth is an advantage from a
noise standpoint, as long as it's not so narrow that it rings for too
long when hit with an impulse. A PLL with long loop time constant might
be a good idea, since it should maintain synchronization through a noise
burst. Other than those generalities, I don't have much to offer. I
built up a simple receiver long ago that allowed me to see the binary
code on a scope, but only late at night. I never pursued perfecting it
to the point where it would be reliable. WWVB increased its power
between then and now, but it's probably still not a piece of cake.

Roy Lewallen, W7EL

Joel Kolstad wrote:
I've been thinking about building a WWVB (time code on 60kHz) receiver, and
wanted to get some suggestions for the architecture. Poking around the web
some, I did find one receiver where the guy built a synchronous detector
using a PLL and VCXO to phase-lock to the 60kHz carrier. Nice idea --
especially since he wanted the 60kHz carrier as a synchronization signal.
However, I just want the time data... so... wouldn't it be easier to build a
mixer at, e.g., 59kHz and then use an envelope detector to get a loud/quiet
audible (1kHz) tone (WWVB reduces power by 10dB to signify 0 bits in its
time code)? It seems to me that this approach avoids the need for the PLL
and VCXO, which is a nice 'reduction' in complexity. Also, since I'll have
a microcontroller around to decode the time code anyway, it can easily
generate the 59kHz signal.

Thanks,
---Joel Kolstad



I would suggest using a shielded loop antenna to help with the local noise
problem.
The loop is directional so it could be oriented to reduce at least one source of
noise.

Bill K7NOM

Roy Lewallen wrote:

I played with that many, many moons ago. The bugaboo is local noise --
QRM from all kinds of devices running from mains power, switching,
arcing, and sparking. The noise was lower late at night when more
gadgets were off, which I'm sure is why the automatic clocks you can get
now do their synchronizing late at night. So I suggest looking at each
architechture for its noise immunity and how it responds when it does
get a burst of noise. Absolute minimum bandwidth is an advantage from a
noise standpoint, as long as it's not so narrow that it rings for too
long when hit with an impulse. A PLL with long loop time constant might
be a good idea, since it should maintain synchronization through a noise
burst. Other than those generalities, I don't have much to offer. I
built up a simple receiver long ago that allowed me to see the binary
code on a scope, but only late at night. I never pursued perfecting it
to the point where it would be reliable. WWVB increased its power
between then and now, but it's probably still not a piece of cake.

Roy Lewallen, W7EL

Joel Kolstad wrote:
I've been thinking about building a WWVB (time code on 60kHz) receiver, and
wanted to get some suggestions for the architecture. Poking around the web
some, I did find one receiver where the guy built a synchronous detector
using a PLL and VCXO to phase-lock to the 60kHz carrier. Nice idea --
especially since he wanted the 60kHz carrier as a synchronization signal.
However, I just want the time data... so... wouldn't it be easier to build a
mixer at, e.g., 59kHz and then use an envelope detector to get a loud/quiet
audible (1kHz) tone (WWVB reduces power by 10dB to signify 0 bits in its
time code)? It seems to me that this approach avoids the need for the PLL
and VCXO, which is a nice 'reduction' in complexity. Also, since I'll have
a microcontroller around to decode the time code anyway, it can easily
generate the 59kHz signal.

Thanks,
---Joel Kolstad



I would suggest using a shielded loop antenna to help with the local noise
problem.
The loop is directional so it could be oriented to reduce at least one source of
noise.

Bill K7NOM

Jack Twilley ) writes:
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"Roy" =3D=3D Roy Lewallen writes:

Roy The noise was lower late at night when more gadgets were off,
Roy which I'm sure is why the automatic clocks you can get now do
Roy their synchronizing late at night.

I thought the reason they sync'ed at night was because of propagation.

Interesting.

Jack.

I thought the reason WWVB was so low down in the spectrum was so propagation
was fairly constant.

Michael VE2BVW

Jack Twilley ) writes:
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"Roy" =3D=3D Roy Lewallen writes:

Roy The noise was lower late at night when more gadgets were off,
Roy which I'm sure is why the automatic clocks you can get now do
Roy their synchronizing late at night.

I thought the reason they sync'ed at night was because of propagation.

Interesting.

Jack.

I thought the reason WWVB was so low down in the spectrum was so propagation
was fairly constant.

Michael VE2BVW

At 60 kHz, there shouldn't be any difference between daytime and
nighttime propagation. Certainly the ionosphere isn't involved.

Roy Lewallen, W7EL

Jack Twilley wrote:
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"Roy" == Roy Lewallen writes:


Roy The noise was lower late at night when more gadgets were off,
Roy which I'm sure is why the automatic clocks you can get now do
Roy their synchronizing late at night.

I thought the reason they sync'ed at night was because of propagation.

Interesting.

Jack.

At 60 kHz, there shouldn't be any difference between daytime and
nighttime propagation. Certainly the ionosphere isn't involved.

Roy Lewallen, W7EL

Jack Twilley wrote:
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Hash: SHA1


"Roy" == Roy Lewallen writes:


Roy The noise was lower late at night when more gadgets were off,
Roy which I'm sure is why the automatic clocks you can get now do
Roy their synchronizing late at night.

I thought the reason they sync'ed at night was because of propagation.

Interesting.

Jack.

The noise was lower late at night when more gadgets were off,
which I'm sure is why the automatic clocks you can get now do
their synchronizing late at night.

I thought the reason they sync'ed at night was because of propagation.

I've occasionally "played" with an "atomic clock" by setting it INcorrectly,
and each has always sync'ed within 10 minutes at ANY time of the day, except
for one which was inside a metal building; it finally sync'ed about noon.

I'm near Topeka, KS, some 400+ miles east and a little south of Boulder, CO.

--Myron, W0PBV.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

The noise was lower late at night when more gadgets were off,
which I'm sure is why the automatic clocks you can get now do
their synchronizing late at night.

I thought the reason they sync'ed at night was because of propagation.

I've occasionally "played" with an "atomic clock" by setting it INcorrectly,
and each has always sync'ed within 10 minutes at ANY time of the day, except
for one which was inside a metal building; it finally sync'ed about noon.

I'm near Topeka, KS, some 400+ miles east and a little south of Boulder, CO.

--Myron, W0PBV.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

On Sat, 04 Oct 2003 18:06:23 -0700, Roy Lewallen
wrote:

At 60 kHz, there shouldn't be any difference between daytime and
nighttime propagation. Certainly the ionosphere isn't involved.

Roy Lewallen, W7EL

Don't forget the daytime LF/MF attenuation in the D-layer, by
preventing it from reaching the E-layer, which sets the LUF (Lowest
Usable Frequency). At night, the D-layer disappears, thus, the signal
can reflect from the E or F layer.

At least the 77,5 kHz Maiflingen standard time transmitter in Germany
is usable to about 2000 .. 2500 km from the transmitter during the
night at least in the winter. However, during the summer nights, the D
layer is in constant sunlight all night nearly 1000 km south of the
arctic circle, which may explain the worse conditions during summer
night, but of course the number of lightnings is also higher during
the summer, increasing the band noise.

Paul OH3LWR

On Sat, 04 Oct 2003 18:06:23 -0700, Roy Lewallen
wrote:

At 60 kHz, there shouldn't be any difference between daytime and
nighttime propagation. Certainly the ionosphere isn't involved.

Roy Lewallen, W7EL

Don't forget the daytime LF/MF attenuation in the D-layer, by
preventing it from reaching the E-layer, which sets the LUF (Lowest
Usable Frequency). At night, the D-layer disappears, thus, the signal
can reflect from the E or F layer.

At least the 77,5 kHz Maiflingen standard time transmitter in Germany
is usable to about 2000 .. 2500 km from the transmitter during the
night at least in the winter. However, during the summer nights, the D
layer is in constant sunlight all night nearly 1000 km south of the
arctic circle, which may explain the worse conditions during summer
night, but of course the number of lightnings is also higher during
the summer, increasing the band noise.

Paul OH3LWR

I'm not at all an expert on propagation. So are you saying that
propagation of 60 kHz signals is via ionospheric skip? E or F layer? I
didn't think the LUF ever got anywhere near 60 kHz at any time.

Roy Lewallen, W7EL

Paul Keinanen wrote:
On Sat, 04 Oct 2003 18:06:23 -0700, Roy Lewallen
wrote:


At 60 kHz, there shouldn't be any difference between daytime and
nighttime propagation. Certainly the ionosphere isn't involved.

Roy Lewallen, W7EL


Don't forget the daytime LF/MF attenuation in the D-layer, by
preventing it from reaching the E-layer, which sets the LUF (Lowest
Usable Frequency). At night, the D-layer disappears, thus, the signal
can reflect from the E or F layer.

At least the 77,5 kHz Maiflingen standard time transmitter in Germany
is usable to about 2000 .. 2500 km from the transmitter during the
night at least in the winter. However, during the summer nights, the D
layer is in constant sunlight all night nearly 1000 km south of the
arctic circle, which may explain the worse conditions during summer
night, but of course the number of lightnings is also higher during
the summer, increasing the band noise.

Paul OH3LWR

I'm not at all an expert on propagation. So are you saying that
propagation of 60 kHz signals is via ionospheric skip? E or F layer? I
didn't think the LUF ever got anywhere near 60 kHz at any time.

Roy Lewallen, W7EL

Paul Keinanen wrote:
On Sat, 04 Oct 2003 18:06:23 -0700, Roy Lewallen
wrote:


At 60 kHz, there shouldn't be any difference between daytime and
nighttime propagation. Certainly the ionosphere isn't involved.

Roy Lewallen, W7EL


Don't forget the daytime LF/MF attenuation in the D-layer, by
preventing it from reaching the E-layer, which sets the LUF (Lowest
Usable Frequency). At night, the D-layer disappears, thus, the signal
can reflect from the E or F layer.

At least the 77,5 kHz Maiflingen standard time transmitter in Germany
is usable to about 2000 .. 2500 km from the transmitter during the
night at least in the winter. However, during the summer nights, the D
layer is in constant sunlight all night nearly 1000 km south of the
arctic circle, which may explain the worse conditions during summer
night, but of course the number of lightnings is also higher during
the summer, increasing the band noise.

Paul OH3LWR

Roy Lewallen ) writes:
At 60 kHz, there shouldn't be any difference between daytime and
nighttime propagation. Certainly the ionosphere isn't involved.

Roy Lewallen, W7EL


Roy,

I believe that even at 60 kHz, propagation is within an earth-ionosphere
waveguide, the height of which is controlled by the sun (60 km during
daylight and 90 km during night).

Precise RF phase comparison is easy at these freqs because the phase
stability of the path is excellent during all daylight conditions, but
there is some random variation at night. It is best to avoid making
measurements (of phase) while the path is only partly in daylight because
of the diurnal shifts in phase as the sunrise-sunset terminator passes
over the radio path (due to the changing height of the waveguide).

The U.S. VLF OMEGA navigation system, the old WWVL (now SK) on 20 kHz, MSF
on 60 kHz, and WWVB on 60 kHz all suffer from these effects.

73,
.... Martin VE3OAT

Roy Lewallen ) writes:
At 60 kHz, there shouldn't be any difference between daytime and
nighttime propagation. Certainly the ionosphere isn't involved.

Roy Lewallen, W7EL


Roy,

I believe that even at 60 kHz, propagation is within an earth-ionosphere
waveguide, the height of which is controlled by the sun (60 km during
daylight and 90 km during night).

Precise RF phase comparison is easy at these freqs because the phase
stability of the path is excellent during all daylight conditions, but
there is some random variation at night. It is best to avoid making
measurements (of phase) while the path is only partly in daylight because
of the diurnal shifts in phase as the sunrise-sunset terminator passes
over the radio path (due to the changing height of the waveguide).

The U.S. VLF OMEGA navigation system, the old WWVL (now SK) on 20 kHz, MSF
on 60 kHz, and WWVB on 60 kHz all suffer from these effects.

73,
.... Martin VE3OAT

For those interested in getting full and complete details of WWVB, go to:

http://www.boulder.nist.gov/timefreq/stations/wwvb.htm

That is the home page for the NIST radio stations and there is a link to
NIST's radio coverage every two hours or so during a 24 hour period
using small hemispere map projections of North and South America.

---

What I am personally interested in is a source for the direct conversion
of WWVB field strength from or to Volts per Meter to confirm the 60 KHz
loop antenna constructed a year ago here. I have a particular reason
since there is some shading effects of nearby-to-residence San Gabriel
Mountain range. Reception is fine, I'm just trying to tie others' numbers
of field strength into the equations for a magnetic loop.

Len Anderson
retired (from regular hours) electronic engineer person

For those interested in getting full and complete details of WWVB, go to:

http://www.boulder.nist.gov/timefreq/stations/wwvb.htm

That is the home page for the NIST radio stations and there is a link to
NIST's radio coverage every two hours or so during a 24 hour period
using small hemispere map projections of North and South America.

---

What I am personally interested in is a source for the direct conversion
of WWVB field strength from or to Volts per Meter to confirm the 60 KHz
loop antenna constructed a year ago here. I have a particular reason
since there is some shading effects of nearby-to-residence San Gabriel
Mountain range. Reception is fine, I'm just trying to tie others' numbers
of field strength into the equations for a magnetic loop.

Len Anderson
retired (from regular hours) electronic engineer person

Bill Janssen wrote:
I would suggest using a shielded loop antenna to help with the local
noise problem.
The loop is directional so it could be oriented to reduce at least one
source of noise.

I was planning to use a coil wound on a ferrite bar core to reduce the
overall size of the antenna, but the web does show people successfully using
large 'air core' loops, as you've suggested. I was thinking of shielding
the ferrite bar antenna by placing it in something along the lines of a
copper pipe with the edge slitted, but apparently it might be bet to enclose
the antenna in a U-shaped piece of metal, such that, oh, say, 1/4 of the
broadside of the antenna is still exposed? I'm not sure why this should
matter, though?

---Joel

Bill Janssen wrote:
I would suggest using a shielded loop antenna to help with the local
noise problem.
The loop is directional so it could be oriented to reduce at least one
source of noise.

I was planning to use a coil wound on a ferrite bar core to reduce the
overall size of the antenna, but the web does show people successfully using
large 'air core' loops, as you've suggested. I was thinking of shielding
the ferrite bar antenna by placing it in something along the lines of a
copper pipe with the edge slitted, but apparently it might be bet to enclose
the antenna in a U-shaped piece of metal, such that, oh, say, 1/4 of the
broadside of the antenna is still exposed? I'm not sure why this should
matter, though?

---Joel

Thanks for the link. That picture brought back vivid memories of times
outdoors in the Rockies in some really attention-getting weather. Whoa,
mama, time to be lookin' for some cover!

Roy Lewallen, W7EL

Avery Fineman wrote:
For those interested in getting full and complete details of WWVB, go to:

http://www.boulder.nist.gov/timefreq/stations/wwvb.htm

That is the home page for the NIST radio stations and there is a link to
NIST's radio coverage every two hours or so during a 24 hour period
using small hemispere map projections of North and South America.
. . .

Thanks for the link. That picture brought back vivid memories of times
outdoors in the Rockies in some really attention-getting weather. Whoa,
mama, time to be lookin' for some cover!

Roy Lewallen, W7EL

Avery Fineman wrote:
For those interested in getting full and complete details of WWVB, go to:

http://www.boulder.nist.gov/timefreq/stations/wwvb.htm

That is the home page for the NIST radio stations and there is a link to
NIST's radio coverage every two hours or so during a 24 hour period
using small hemispere map projections of North and South America.
. . .

In article , Roy Lewallen
writes:

Thanks for the link. That picture brought back vivid memories of times
outdoors in the Rockies in some really attention-getting weather. Whoa,
mama, time to be lookin' for some cover!

Roy Lewallen, W7EL

Avery Fineman wrote:
For those interested in getting full and complete details of WWVB, go
to:

http://www.boulder.nist.gov/timefreq/stations/wwvb.htm

I'm sure the photographer for NIST was counting on that attention-getting
weather for the WWVB page's photogenic qualities. :-)

A link on the WWVB page has some typical field strengths given for
various locations in the USA along with a tabulation of daily changes
in that field strength level. There's also a log of outages of WWVB for
those who want to check if they are on when you want them to be.

Almost any Internet search engine will turn up a surprising number of
links to 60 KHz loop antennas built by all sorts of electronic hobbyists.
I did that search a year ago when preparing to build my WWVB loop
receiver and phase-locker for the frequency counter timebase standard.

One of the most innovative in my estimation was the loop built on an
unused bicycle wheel rim (spokes removed). A couple of cuts of a
hacksaw put the gap in the wheel rim to prevent the "shorted turn
effect" from happening. The wheel rim should be a very sturdy former
for winding heavy coil wire around it. A strip of plastic provided
mechanical support for the gap in the wheel. If memory serves, it was
done in San Diego, CA, area and mounted outside under a patio cover.

My own loop is 58 1/2 turns of #14 AWG THHN electrical wire self-
supporting with a mean diameter of 2 feet, 8 inches, then bound with
cheap twine that was well varnished with McCloskey's "Gym-Seal"
floor varnish. The electrostatic shielding was provided by heavy-grade
kitchen aluminum foil (with a gap, of course) that was bound with a
second application of twine, then varnished. Q at resonance is about
44, good enough for about 1.4 KHz BW by itself. With 58 1/2 turns,
inductance is 5.6 to 5.7 milliHenry. Distributed capacity is about 390
pFd, not too bad considering that winding took all but 9 feet of a 500
foot spool (purchased at Home Depot for $14).

The loop is mounted in the attic space above the center room of the
house with half of that room as the workshop. That attic space is
closed off from the rest of the attic by recent roof remodeling so it has
become essentially waterproof now...construction was originally done
to work in direct rain, tested only with liberal garden hose sprinkling
and measuring of characteristics. The loop connections are balanced
above ground with the electrostatic shield at ground potential and two
12 foot RG-59 TV cables are used something like Twinax to a
balanced input FET differential amplifier stage below in the workshop.
Resonating at 60 KHz is done with a sacrificed dual variable capacitor
in the differential FET amplifier. Worked out well and I can't observe any
funny spikes from appliances or other non-WWVB signal things after
the FET stage. 60 KHz signal voltage across the loop at resonance is
estimated at about 90 to 120 microVolts. Location here is northern
Los Angeles in the Verdugo Hills (a mile of hills between here and
Boulder, CO)..

There are two Oregon Scientific radio clocks in the house, a small
one about 4 years old that indicates it has solid automatic updating.
Has a small "loopstick" like gizmo inside as the antenna. A large
one in the office room, very visible from 12 feet, 1 year old, misses
a midnight update about once every two weeks. The small one is
"solid copy" all the time. Don't know what the large one uses for a
loopstick antenna...wife won't let me open it up to look. :-)

Ferrite/powdered-iron core "antennas" used in consumer market
radio clocks seem to work very well. Neither is very directional.
The little radio clock was $20 retail and the big one about $25.
Battery life is over a year, closer to two years. Both have built-
in calendars (leap year is probably derived directly from WWVB
data coding).

Len Anderson
retired (from regular hours) electronic engineer person

In article , Roy Lewallen
writes:

Thanks for the link. That picture brought back vivid memories of times
outdoors in the Rockies in some really attention-getting weather. Whoa,
mama, time to be lookin' for some cover!

Roy Lewallen, W7EL

Avery Fineman wrote:
For those interested in getting full and complete details of WWVB, go
to:

http://www.boulder.nist.gov/timefreq/stations/wwvb.htm

I'm sure the photographer for NIST was counting on that attention-getting
weather for the WWVB page's photogenic qualities. :-)

A link on the WWVB page has some typical field strengths given for
various locations in the USA along with a tabulation of daily changes
in that field strength level. There's also a log of outages of WWVB for
those who want to check if they are on when you want them to be.

Almost any Internet search engine will turn up a surprising number of
links to 60 KHz loop antennas built by all sorts of electronic hobbyists.
I did that search a year ago when preparing to build my WWVB loop
receiver and phase-locker for the frequency counter timebase standard.

One of the most innovative in my estimation was the loop built on an
unused bicycle wheel rim (spokes removed). A couple of cuts of a
hacksaw put the gap in the wheel rim to prevent the "shorted turn
effect" from happening. The wheel rim should be a very sturdy former
for winding heavy coil wire around it. A strip of plastic provided
mechanical support for the gap in the wheel. If memory serves, it was
done in San Diego, CA, area and mounted outside under a patio cover.

My own loop is 58 1/2 turns of #14 AWG THHN electrical wire self-
supporting with a mean diameter of 2 feet, 8 inches, then bound with
cheap twine that was well varnished with McCloskey's "Gym-Seal"
floor varnish. The electrostatic shielding was provided by heavy-grade
kitchen aluminum foil (with a gap, of course) that was bound with a
second application of twine, then varnished. Q at resonance is about
44, good enough for about 1.4 KHz BW by itself. With 58 1/2 turns,
inductance is 5.6 to 5.7 milliHenry. Distributed capacity is about 390
pFd, not too bad considering that winding took all but 9 feet of a 500
foot spool (purchased at Home Depot for $14).

The loop is mounted in the attic space above the center room of the
house with half of that room as the workshop. That attic space is
closed off from the rest of the attic by recent roof remodeling so it has
become essentially waterproof now...construction was originally done
to work in direct rain, tested only with liberal garden hose sprinkling
and measuring of characteristics. The loop connections are balanced
above ground with the electrostatic shield at ground potential and two
12 foot RG-59 TV cables are used something like Twinax to a
balanced input FET differential amplifier stage below in the workshop.
Resonating at 60 KHz is done with a sacrificed dual variable capacitor
in the differential FET amplifier. Worked out well and I can't observe any
funny spikes from appliances or other non-WWVB signal things after
the FET stage. 60 KHz signal voltage across the loop at resonance is
estimated at about 90 to 120 microVolts. Location here is northern
Los Angeles in the Verdugo Hills (a mile of hills between here and
Boulder, CO)..

There are two Oregon Scientific radio clocks in the house, a small
one about 4 years old that indicates it has solid automatic updating.
Has a small "loopstick" like gizmo inside as the antenna. A large
one in the office room, very visible from 12 feet, 1 year old, misses
a midnight update about once every two weeks. The small one is
"solid copy" all the time. Don't know what the large one uses for a
loopstick antenna...wife won't let me open it up to look. :-)

Ferrite/powdered-iron core "antennas" used in consumer market
radio clocks seem to work very well. Neither is very directional.
The little radio clock was $20 retail and the big one about $25.
Battery life is over a year, closer to two years. Both have built-
in calendars (leap year is probably derived directly from WWVB
data coding).

Len Anderson
retired (from regular hours) electronic engineer person

Hi Avery,

Avery Fineman wrote:
One of the most innovative in my estimation was the loop built on an
unused bicycle wheel rim (spokes removed).

Indeed. I saw one of those he http://lakeweb.com/rf/wwvb/ (may or may
not be the same one you found), and it is a clever idea. I'm thinking now I
might build one like that as well as a ferrite rod version to compare with;
since the ferrite will increase the effective area of the antenna by the
square of its effective relative permeability, I want to believe that a 1/2"
ferrite rod can compete with... well... at least an air core loop, uh... the
size of your hand? (I don't have various references here with me to start
looking up the effective relative permeability of a ferrite rod of a given
l/d ratio... hopefully in the ballpark of 20-50...)

I also found that people did occasionally ask about really large diameter
(1") ferrite cores, and while the usual response was that you could, of
course, pack a bunch of smaller rods together to make a big one, apparently
no one has the considerable $$$ around to build, say, a coffee can sized
ferrite core antenna. Would be something to see though! Anyone want to
donate some fat ferrite rods to me? :-)

My own loop is 58 1/2 turns of #14 AWG THHN electrical wire self-
supporting with a mean diameter of 2 feet, 8 inches, then bound with
cheap twine that was well varnished with McCloskey's "Gym-Seal"
floor varnish. The electrostatic shielding was provided by heavy-grade
kitchen aluminum foil (with a gap, of course) that was bound with a
second application of twine, then varnished. Q at resonance is about
44, good enough for about 1.4 KHz BW by itself.

Not bad at all!

Worked out well
and I can't observe any funny spikes from appliances or other
non-WWVB signal things after the FET stage.

That's good to hear; noise seems to be a common concern.

I believe you said your receiver was a synchronous design, correct? I'm
still liking the envelope detector approach, but I've yet to hear about
anyone successfully employing this (simpler) method.

60 KHz signal voltage
across the loop at resonance is estimated at about 90 to 120
microVolts.

I don't suppose you have an estimate of your signal to noise ratio?

Location here is northern Los Angeles in the Verdugo
Hills (a mile of hills between here and Boulder, CO)..

I'm in Corvallis, Oregon, which -- eyeballing it on a map -- is perhaps half
again as far from Boulder. I have one of the inexpensive self-setting
clocks that does work pretty reliably _if keep in certain positions within
my house_. I've read that these also set themselves at night when the SNR
is significantly higher too.

Ferrite/powdered-iron core "antennas" used in consumer market
radio clocks seem to work very well.

I was going to get some of the 1/2"x4" or 7" rods from Ocean State
Electronics he http://www.oselectronics.com/ose_p88.htm ... they also
have some inexpensive pre-wound rods meant for AM radios
(http://www.oselectronics.com/ose_p91.htm), but they're apparently tuned for
the AM broadcast band and therefore I'd have to re-wind the things anyway.

This is hopefully going to end up as a class project and therefore the goal
of learning how to build your own antenna and receiver is the reason I'm not
intending to just go and use someone's "all in one" WWVB receiver IC (even
though colleges seem to push that approach these days... but then _someone_
had to design that IC, right!?).

---Joel Kolstad

Hi Avery,

Avery Fineman wrote:
One of the most innovative in my estimation was the loop built on an
unused bicycle wheel rim (spokes removed).

Indeed. I saw one of those he http://lakeweb.com/rf/wwvb/ (may or may
not be the same one you found), and it is a clever idea. I'm thinking now I
might build one like that as well as a ferrite rod version to compare with;
since the ferrite will increase the effective area of the antenna by the
square of its effective relative permeability, I want to believe that a 1/2"
ferrite rod can compete with... well... at least an air core loop, uh... the
size of your hand? (I don't have various references here with me to start
looking up the effective relative permeability of a ferrite rod of a given
l/d ratio... hopefully in the ballpark of 20-50...)

I also found that people did occasionally ask about really large diameter
(1") ferrite cores, and while the usual response was that you could, of
course, pack a bunch of smaller rods together to make a big one, apparently
no one has the considerable $$$ around to build, say, a coffee can sized
ferrite core antenna. Would be something to see though! Anyone want to
donate some fat ferrite rods to me? :-)

My own loop is 58 1/2 turns of #14 AWG THHN electrical wire self-
supporting with a mean diameter of 2 feet, 8 inches, then bound with
cheap twine that was well varnished with McCloskey's "Gym-Seal"
floor varnish. The electrostatic shielding was provided by heavy-grade
kitchen aluminum foil (with a gap, of course) that was bound with a
second application of twine, then varnished. Q at resonance is about
44, good enough for about 1.4 KHz BW by itself.

Not bad at all!

Worked out well
and I can't observe any funny spikes from appliances or other
non-WWVB signal things after the FET stage.

That's good to hear; noise seems to be a common concern.

I believe you said your receiver was a synchronous design, correct? I'm
still liking the envelope detector approach, but I've yet to hear about
anyone successfully employing this (simpler) method.

60 KHz signal voltage
across the loop at resonance is estimated at about 90 to 120
microVolts.

I don't suppose you have an estimate of your signal to noise ratio?

Location here is northern Los Angeles in the Verdugo
Hills (a mile of hills between here and Boulder, CO)..

I'm in Corvallis, Oregon, which -- eyeballing it on a map -- is perhaps half
again as far from Boulder. I have one of the inexpensive self-setting
clocks that does work pretty reliably _if keep in certain positions within
my house_. I've read that these also set themselves at night when the SNR
is significantly higher too.

Ferrite/powdered-iron core "antennas" used in consumer market
radio clocks seem to work very well.

I was going to get some of the 1/2"x4" or 7" rods from Ocean State
Electronics he http://www.oselectronics.com/ose_p88.htm ... they also
have some inexpensive pre-wound rods meant for AM radios
(http://www.oselectronics.com/ose_p91.htm), but they're apparently tuned for
the AM broadcast band and therefore I'd have to re-wind the things anyway.

This is hopefully going to end up as a class project and therefore the goal
of learning how to build your own antenna and receiver is the reason I'm not
intending to just go and use someone's "all in one" WWVB receiver IC (even
though colleges seem to push that approach these days... but then _someone_
had to design that IC, right!?).

---Joel Kolstad

In article , "Joel Kolstad"
writes:

Avery Fineman wrote:
One of the most innovative in my estimation was the loop built on an
unused bicycle wheel rim (spokes removed).

Indeed. I saw one of those he http://lakeweb.com/rf/wwvb/ (may or may
not be the same one you found), and it is a clever idea. I'm thinking now I
might build one like that as well as a ferrite rod version to compare with;
since the ferrite will increase the effective area of the antenna by the
square of its effective relative permeability, I want to believe that a 1/2"
ferrite rod can compete with... well... at least an air core loop, uh... the
size of your hand? (I don't have various references here with me to start
looking up the effective relative permeability of a ferrite rod of a given
l/d ratio... hopefully in the ballpark of 20-50...)

Sounds good. I've not experimented with ferrite or powdered-iron
core antennas for my project. My loop was based more on the fact
that there was attic space above the interior workshop and the trap
door diagonal dimension set the maximum loop diameter to 2' 10".
#14 electrical wire was actually cheaper than purchaseable coil
wire for 500 feet and was a relatively calculable-before-build thing.
I could have put in a 5 foot diameter loop but would have to dismantle
a few things to get it there or spend time bent over while constructing
it. :-) [winding and wrapping took a LOT longer than expected!]

I also found that people did occasionally ask about really large diameter
(1") ferrite cores, and while the usual response was that you could, of
course, pack a bunch of smaller rods together to make a big one, apparently
no one has the considerable $$$ around to build, say, a coffee can sized
ferrite core antenna. Would be something to see though! Anyone want to
donate some fat ferrite rods to me? :-)

My own loop is 58 1/2 turns of #14 AWG THHN electrical wire self-
supporting with a mean diameter of 2 feet, 8 inches, then bound with
cheap twine that was well varnished with McCloskey's "Gym-Seal"
floor varnish. The electrostatic shielding was provided by heavy-grade
kitchen aluminum foil (with a gap, of course) that was bound with a
second application of twine, then varnished. Q at resonance is about
44, good enough for about 1.4 KHz BW by itself.

Not bad at all!

Worked out well
and I can't observe any funny spikes from appliances or other
non-WWVB signal things after the FET stage.

That's good to hear; noise seems to be a common concern.

I believe you said your receiver was a synchronous design, correct? I'm
still liking the envelope detector approach, but I've yet to hear about
anyone successfully employing this (simpler) method.

My project is specifically for deriving the 60 KHz carrier, as clean as
possible prior to mixing-dividing etc. to compare the frequency
counter timebase frequency of 10 MHz. With two commercial radio
clocks on hand, WWV over the Icom R-70 for time hacks, wasn't any
desire to decode the time signal.

To get a narrow receiving bandwidth "raw," the tuned loop handles the
initial selectivity. A differential FET with tuned transformer output both
gets rid of some common-mode RF pickup and the transformer Q of
just about 30 drops the far-frequency attenuation more (bandwidth of
the transformer is roughly 2 KHz, wider than loop alone). From there
on things are quite different.

The amplified, "wide" bandwidth WWVB signal is fed to an old MC1350P
video-RF differential amplifier with a local oscillator at about 246 KHz
into
the AGC voltage pin. That makes it an active balanced mixer. The
output of that goes to a single quartz crystal filter at 186 KHz...an old
surplus xtal acquired decades ago, presumably from a timebase or
marker crystal for a military radar set of ancient vintage. A second
MC1350P mixerf, fed with the same 246 KHz LO but the output tuned
to 60 KHz downconverts to the original frequency.

The two mixers need to have the LO injection with at least 30 db of
isolation between the two...takes some playing around and I got about
40 db. The up-conversion and down-conversion was to use a crystal
filter at a frequency different than 60 KHz (avoids re-radiation pickup in
the loop for one thing or other stuff in the breadboard stage). The crystal
filter is still being played with but the basic circuit is just series-
resonance at a single frequency, looking for the narrowest bandwidth
possible. Getting about 5 Hz of -3 db bandwidth right now and am having
to fuss with temperature stability of the L-C tuned LO. Gets a bit fussy
to test out that narrow a bandwidth...:-)

Note: The heterodyning (mixing) process doesn't change the relative
phase of a frequency-changed signal. A second heterodyne back to
the original frequency retains the original relative phase. The trick
there is to get isolation from one LO injection port to the other. That
avoids any feed-through which can spoil the crystal filtering action.
I use a couple more MC1350s to split out from the L-C transistor
oscillator with supply pins separately decoupled and gains set low
by using very low collector load resistors.

I might be satisfied with a 10 Hz bandwidth overall if the fussing-around
period eats up too much time. Right now it looks like a very clean
RF carrier waveform with annoying 1 second bounce up and down when
viewed on a scope. I'm planning on adding a limiter stage or two following
which will remove the modulation almost fully (!). The MC1350P (an old
Motorola part based on their metal can MC1590) makes an excellent
limiter when over-driven.

60 KHz signal voltage
across the loop at resonance is estimated at about 90 to 120
microVolts.

I don't suppose you have an estimate of your signal to noise ratio?

No. I'm looking for the carrier as clean as I can get it. There's zilch
front-end noise. There are some occaisional "bumps" from impulse
stuff from somewhere but nothing from horizontal TV sweep 4th
harmonic at ~63 KHz. Closest TV set is about 15 feet away diagonal.

Offhand, I'd say the S:N ratio is consistent with a 10 Hz bandwidth
at -3 db points. That would be fine if I were demodulating the WWVB
time code changing at a 1 Hz rate.

Location here is northern Los Angeles in the Verdugo
Hills (a mile of hills between here and Boulder, CO)..

I'm in Corvallis, Oregon, which -- eyeballing it on a map -- is perhaps half
again as far from Boulder. I have one of the inexpensive self-setting
clocks that does work pretty reliably _if keep in certain positions within
my house_. I've read that these also set themselves at night when the SNR
is significantly higher too.

Their automatic sensing varies with the manufacturer. NIST has some
info (in a FAQ page?) on their site. The little Oregon Scientific unit
here (older one) checks itself every 8 hours, the larger new one (by same
company) checks itself in the hour after midnight.

Ferrite/powdered-iron core "antennas" used in consumer market
radio clocks seem to work very well.

I was going to get some of the 1/2"x4" or 7" rods from Ocean State
Electronics he http://www.oselectronics.com/ose_p88.htm ... they also
have some inexpensive pre-wound rods meant for AM radios
(http://www.oselectronics.com/ose_p91.htm), but they're apparently tuned for
the AM broadcast band and therefore I'd have to re-wind the things anyway.

Couple of things there. Core permeability may be different at 60 KHz
versus the 550 KHz low frequency of AM BC band. If it is okay then
you can get away without rewinding the coil on it, just retune it with
more capacitance if your input circuit can stand the lower impedance.

At 60 KHz you can use a wide-range audio test oscillator for checking
resonance Q, measuring inductance, etc. I was using an ancient
Heathkit audio oscillator (Wien bridge type) with the 5-digit frequency
counter built into a French-made DVM newly purchased from Mouser.

This is hopefully going to end up as a class project and therefore the goal
of learning how to build your own antenna and receiver is the reason I'm not
intending to just go and use someone's "all in one" WWVB receiver IC (even
though colleges seem to push that approach these days... but then _someone_
had to design that IC, right!?).

Hans Summers has a nice section on his website in the UK that has
full particulars of his 1991 first-year university project of a 60 KHz
receiver-decoder for the Rugby station there. He used discrete TTL
packages for the entire decoder! [Rugby modulation code a bit
different compared to WWVB]

http://www.hanssummers.com/electroni...o/radioclk.htm

Hans (who appears in here from time to time) has _everything_ on
that project available there. Interesting!

If I type the link incorrect, just get www.hanssummers.com and
navigate from there. Interesting website with lots of different projects
well-described.

If I were going for a radio clock project, I'd get a reasonably-clean
signal at 60 KHz by analog means with a bandwidth of 10 to 50 Hz
on the output then use one of the many PIC microcontrollers to do
the decoding...and also readout control. Microcircuits has free
development software for download that works in any PC. Decoding
algorithms will be roughly the same whether done in software or
hardware and (in my estimation) your own software development can
be as much fun as handling lots of hardware. Your mileage may vary.

Have fun. Things are a bit different working with a very fixed frequency
station at LF with very slow modulation rates! :-)

Len Anderson
retired (from regular hours) electronic engineer person

In article , "Joel Kolstad"
writes:

Avery Fineman wrote:
One of the most innovative in my estimation was the loop built on an
unused bicycle wheel rim (spokes removed).

Indeed. I saw one of those he http://lakeweb.com/rf/wwvb/ (may or may
not be the same one you found), and it is a clever idea. I'm thinking now I
might build one like that as well as a ferrite rod version to compare with;
since the ferrite will increase the effective area of the antenna by the
square of its effective relative permeability, I want to believe that a 1/2"
ferrite rod can compete with... well... at least an air core loop, uh... the
size of your hand? (I don't have various references here with me to start
looking up the effective relative permeability of a ferrite rod of a given
l/d ratio... hopefully in the ballpark of 20-50...)

Sounds good. I've not experimented with ferrite or powdered-iron
core antennas for my project. My loop was based more on the fact
that there was attic space above the interior workshop and the trap
door diagonal dimension set the maximum loop diameter to 2' 10".
#14 electrical wire was actually cheaper than purchaseable coil
wire for 500 feet and was a relatively calculable-before-build thing.
I could have put in a 5 foot diameter loop but would have to dismantle
a few things to get it there or spend time bent over while constructing
it. :-) [winding and wrapping took a LOT longer than expected!]

I also found that people did occasionally ask about really large diameter
(1") ferrite cores, and while the usual response was that you could, of
course, pack a bunch of smaller rods together to make a big one, apparently
no one has the considerable $$$ around to build, say, a coffee can sized
ferrite core antenna. Would be something to see though! Anyone want to
donate some fat ferrite rods to me? :-)

My own loop is 58 1/2 turns of #14 AWG THHN electrical wire self-
supporting with a mean diameter of 2 feet, 8 inches, then bound with
cheap twine that was well varnished with McCloskey's "Gym-Seal"
floor varnish. The electrostatic shielding was provided by heavy-grade
kitchen aluminum foil (with a gap, of course) that was bound with a
second application of twine, then varnished. Q at resonance is about
44, good enough for about 1.4 KHz BW by itself.

Not bad at all!

Worked out well
and I can't observe any funny spikes from appliances or other
non-WWVB signal things after the FET stage.

That's good to hear; noise seems to be a common concern.

I believe you said your receiver was a synchronous design, correct? I'm
still liking the envelope detector approach, but I've yet to hear about
anyone successfully employing this (simpler) method.

My project is specifically for deriving the 60 KHz carrier, as clean as
possible prior to mixing-dividing etc. to compare the frequency
counter timebase frequency of 10 MHz. With two commercial radio
clocks on hand, WWV over the Icom R-70 for time hacks, wasn't any
desire to decode the time signal.

To get a narrow receiving bandwidth "raw," the tuned loop handles the
initial selectivity. A differential FET with tuned transformer output both
gets rid of some common-mode RF pickup and the transformer Q of
just about 30 drops the far-frequency attenuation more (bandwidth of
the transformer is roughly 2 KHz, wider than loop alone). From there
on things are quite different.

The amplified, "wide" bandwidth WWVB signal is fed to an old MC1350P
video-RF differential amplifier with a local oscillator at about 246 KHz
into
the AGC voltage pin. That makes it an active balanced mixer. The
output of that goes to a single quartz crystal filter at 186 KHz...an old
surplus xtal acquired decades ago, presumably from a timebase or
marker crystal for a military radar set of ancient vintage. A second
MC1350P mixerf, fed with the same 246 KHz LO but the output tuned
to 60 KHz downconverts to the original frequency.

The two mixers need to have the LO injection with at least 30 db of
isolation between the two...takes some playing around and I got about
40 db. The up-conversion and down-conversion was to use a crystal
filter at a frequency different than 60 KHz (avoids re-radiation pickup in
the loop for one thing or other stuff in the breadboard stage). The crystal
filter is still being played with but the basic circuit is just series-
resonance at a single frequency, looking for the narrowest bandwidth
possible. Getting about 5 Hz of -3 db bandwidth right now and am having
to fuss with temperature stability of the L-C tuned LO. Gets a bit fussy
to test out that narrow a bandwidth...:-)

Note: The heterodyning (mixing) process doesn't change the relative
phase of a frequency-changed signal. A second heterodyne back to
the original frequency retains the original relative phase. The trick
there is to get isolation from one LO injection port to the other. That
avoids any feed-through which can spoil the crystal filtering action.
I use a couple more MC1350s to split out from the L-C transistor
oscillator with supply pins separately decoupled and gains set low
by using very low collector load resistors.

I might be satisfied with a 10 Hz bandwidth overall if the fussing-around
period eats up too much time. Right now it looks like a very clean
RF carrier waveform with annoying 1 second bounce up and down when
viewed on a scope. I'm planning on adding a limiter stage or two following
which will remove the modulation almost fully (!). The MC1350P (an old
Motorola part based on their metal can MC1590) makes an excellent
limiter when over-driven.

60 KHz signal voltage
across the loop at resonance is estimated at about 90 to 120
microVolts.

I don't suppose you have an estimate of your signal to noise ratio?

No. I'm looking for the carrier as clean as I can get it. There's zilch
front-end noise. There are some occaisional "bumps" from impulse
stuff from somewhere but nothing from horizontal TV sweep 4th
harmonic at ~63 KHz. Closest TV set is about 15 feet away diagonal.

Offhand, I'd say the S:N ratio is consistent with a 10 Hz bandwidth
at -3 db points. That would be fine if I were demodulating the WWVB
time code changing at a 1 Hz rate.

Location here is northern Los Angeles in the Verdugo
Hills (a mile of hills between here and Boulder, CO)..

I'm in Corvallis, Oregon, which -- eyeballing it on a map -- is perhaps half
again as far from Boulder. I have one of the inexpensive self-setting
clocks that does work pretty reliably _if keep in certain positions within
my house_. I've read that these also set themselves at night when the SNR
is significantly higher too.

Their automatic sensing varies with the manufacturer. NIST has some
info (in a FAQ page?) on their site. The little Oregon Scientific unit
here (older one) checks itself every 8 hours, the larger new one (by same
company) checks itself in the hour after midnight.

Ferrite/powdered-iron core "antennas" used in consumer market
radio clocks seem to work very well.

I was going to get some of the 1/2"x4" or 7" rods from Ocean State
Electronics he http://www.oselectronics.com/ose_p88.htm ... they also
have some inexpensive pre-wound rods meant for AM radios
(http://www.oselectronics.com/ose_p91.htm), but they're apparently tuned for
the AM broadcast band and therefore I'd have to re-wind the things anyway.

Couple of things there. Core permeability may be different at 60 KHz
versus the 550 KHz low frequency of AM BC band. If it is okay then
you can get away without rewinding the coil on it, just retune it with
more capacitance if your input circuit can stand the lower impedance.

At 60 KHz you can use a wide-range audio test oscillator for checking
resonance Q, measuring inductance, etc. I was using an ancient
Heathkit audio oscillator (Wien bridge type) with the 5-digit frequency
counter built into a French-made DVM newly purchased from Mouser.

This is hopefully going to end up as a class project and therefore the goal
of learning how to build your own antenna and receiver is the reason I'm not
intending to just go and use someone's "all in one" WWVB receiver IC (even
though colleges seem to push that approach these days... but then _someone_
had to design that IC, right!?).

Hans Summers has a nice section on his website in the UK that has
full particulars of his 1991 first-year university project of a 60 KHz
receiver-decoder for the Rugby station there. He used discrete TTL
packages for the entire decoder! [Rugby modulation code a bit
different compared to WWVB]

http://www.hanssummers.com/electroni...o/radioclk.htm

Hans (who appears in here from time to time) has _everything_ on
that project available there. Interesting!

If I type the link incorrect, just get www.hanssummers.com and
navigate from there. Interesting website with lots of different projects
well-described.

If I were going for a radio clock project, I'd get a reasonably-clean
signal at 60 KHz by analog means with a bandwidth of 10 to 50 Hz
on the output then use one of the many PIC microcontrollers to do
the decoding...and also readout control. Microcircuits has free
development software for download that works in any PC. Decoding
algorithms will be roughly the same whether done in software or
hardware and (in my estimation) your own software development can
be as much fun as handling lots of hardware. Your mileage may vary.

Have fun. Things are a bit different working with a very fixed frequency
station at LF with very slow modulation rates! :-)

Len Anderson
retired (from regular hours) electronic engineer person

I read an article about WWVB reception for a frequency standard that made
use of a zero crossing detector to detect the 60 KHz signal.

His point was that many detection schemes can get a false count now and
then due to the 10 dB drop in signal strength that WWVB uses to encode the
time information.

Apparently, the zero crossings are quite stable regardless of the
amplitude change.

For a system to recover the time information, I'd be inclined to simply
amplify the incoming and then use a diode detector of some sort. Well, that
and a SLOW AGC system...

I do not think it would need anything as complex as a synchronous
detector since any changes in the propogation of 60 KHz is very slow.
Admitted, the occasional noise burst may result in a false pulse now and
then.

Since you are likely to feed the signal into a computer of some sort to
decode the pulses to a time signal, you can add some programming to handle
the occasional false pulse.



Jim Pennell
N6BIU

I read an article about WWVB reception for a frequency standard that made
use of a zero crossing detector to detect the 60 KHz signal.

His point was that many detection schemes can get a false count now and
then due to the 10 dB drop in signal strength that WWVB uses to encode the
time information.

Apparently, the zero crossings are quite stable regardless of the
amplitude change.

For a system to recover the time information, I'd be inclined to simply
amplify the incoming and then use a diode detector of some sort. Well, that
and a SLOW AGC system...

I do not think it would need anything as complex as a synchronous
detector since any changes in the propogation of 60 KHz is very slow.
Admitted, the occasional noise burst may result in a false pulse now and
then.

Since you are likely to feed the signal into a computer of some sort to
decode the pulses to a time signal, you can add some programming to handle
the occasional false pulse.



Jim Pennell
N6BIU

Thanks for that most informative response, Avery, and also the link to Hans'
project.

Hopefully next week I'll get around to constructing my antenna (need to
visit a bike store and ask for busted rims this weekend... :-) ). From the
signal strengths you were quoting (100uV), it seems as though it's iffy
whether or not you'd see anything at all taking the output of the antenna
(with resonating capacitor) and feeding it directly to a spectrum analyzer
(since we're looking at, oh, -70 to -80dBm into 50 ohms, which is starting
to push the noise floor of at least one spectrum analyzer I have available
to use). If there's nothing visible at that point, however, hopefully after
a differential FET amplifier as you suggested the signal will be visible.
(I find it very reassuring to be able to see you actually have some signal
present at each point of a porject's development...)

---Joel

Thanks for that most informative response, Avery, and also the link to Hans'
project.

Hopefully next week I'll get around to constructing my antenna (need to
visit a bike store and ask for busted rims this weekend... :-) ). From the
signal strengths you were quoting (100uV), it seems as though it's iffy
whether or not you'd see anything at all taking the output of the antenna
(with resonating capacitor) and feeding it directly to a spectrum analyzer
(since we're looking at, oh, -70 to -80dBm into 50 ohms, which is starting
to push the noise floor of at least one spectrum analyzer I have available
to use). If there's nothing visible at that point, however, hopefully after
a differential FET amplifier as you suggested the signal will be visible.
(I find it very reassuring to be able to see you actually have some signal
present at each point of a porject's development...)

---Joel

In article , "Joel Kolstad"
writes:

Thanks for that most informative response, Avery, and also the link to Hans'
project.

Hopefully next week I'll get around to constructing my antenna (need to
visit a bike store and ask for busted rims this weekend... :-) ). From the
signal strengths you were quoting (100uV), it seems as though it's iffy
whether or not you'd see anything at all taking the output of the antenna
(with resonating capacitor) and feeding it directly to a spectrum analyzer
(since we're looking at, oh, -70 to -80dBm into 50 ohms, which is starting
to push the noise floor of at least one spectrum analyzer I have available
to use). If there's nothing visible at that point, however, hopefully after
a differential FET amplifier as you suggested the signal will be visible.
(I find it very reassuring to be able to see you actually have some signal
present at each point of a porject's development...)