I am making a WWVB receiver to compare the diurnal phase shift with GPS.

Ferrite loop antennas are available on Amazon, but they are fixed frequency
and I need to find a way to tune them.

I wonder if a magnetic field will affect the permeability so I can shift the
frequency with a small magnet? It would be followed by a 60KHz xtal filter to
narrow the bandwidth, so a reduction in Q is acceptable.

The assembly would have to be in a temperature-controlled environment, but
that's fairly easy.

Any thoughts?

On 18.12.21 20.39, Jan Frank wrote:
> I am making a WWVB receiver to compare the diurnal phase shift with GPS.
>
> Ferrite loop antennas are available on Amazon, but they are fixed frequency
> and I need to find a way to tune them.
>
> I wonder if a magnetic field will affect the permeability so I can shift the
> frequency with a small magnet? It would be followed by a 60KHz xtal filter to
> narrow the bandwidth, so a reduction in Q is acceptable.
>
> The assembly would have to be in a temperature-controlled environment, but
> that's fairly easy.
>
> Any thoughts?

You can alter the effective permeability by partially saturating
the core, but it will spoil the antenna function.

The ferrite stick with coil is just an inductance, and its resonant
frequency is dependent of the companion capacitance. The target
frequency should not be too far from the design frequency, as the
circuit impedance will be far off. Also, the ferrite material works
well on the design frequency, and it may show more losses than desired
if the frequency is far off the original.

A crystal filter may be a not too good idea, as it is by nature
narrow-band with accompanying wild phase/delay characteristic
wit even slight frequency differences.

You may be better off with some kind of superheterodyne approach.

--

-TV

On Sat, 18 Dec 2021 18:39:31 -0000 (UTC), Jan Frank <nospam@not.com>
wrote:

>I am making a WWVB receiver to compare the diurnal phase shift with GPS.
>
>Ferrite loop antennas are available on Amazon, but they are fixed frequency
>and I need to find a way to tune them.
>
>I wonder if a magnetic field will affect the permeability so I can shift the
>frequency with a small magnet? It would be followed by a 60KHz xtal filter to
>narrow the bandwidth, so a reduction in Q is acceptable.
>
>The assembly would have to be in a temperature-controlled environment, but
>that's fairly easy.
>
>Any thoughts?

How about a giant loop antenna? Use multiconductor shielded cable.
Lots of pickup area.

Normally one would ground one end of the shield, but why not resonate
the shield?

--

I yam what I yam - Popeye

jlarkin@highlandsniptechnology.com wrote:

> On Sat, 18 Dec 2021 18:39:31 -0000 (UTC), Jan Frank <nospam@not.com>
> wrote:
>
>>I am making a WWVB receiver to compare the diurnal phase shift with GPS.
>>
>>Ferrite loop antennas are available on Amazon, but they are fixed
>>frequency and I need to find a way to tune them.
>>
>>I wonder if a magnetic field will affect the permeability so I can shift
>>the frequency with a small magnet? It would be followed by a 60KHz xtal
>>filter to narrow the bandwidth, so a reduction in Q is acceptable.
>>
>>The assembly would have to be in a temperature-controlled environment,
>>but that's fairly easy.
>>
>>Any thoughts?
>
> How about a giant loop antenna? Use multiconductor shielded cable.
> Lots of pickup area.
>
> Normally one would ground one end of the shield, but why not resonate
> the shield?

Thanks for the suggestion, but I don't need a large pickup area. I have a
number of WWVB clocks, including two Casio Waveceptor wrist watches. They
have a tiny ferrite antenna to fit in the small case, but still have enough
signal to synchronize perfectly every night:

https://www.amazon.ca/s?k=casio+waveceptor+watches+men

The Amazon ferrite loop is much larger and should provide plenty of signal:

https://www.amazon.ca/gp/product/B01KH3VEGS/

In addition there is no way to trim the resonance of a large loop except by
changing the capacitor. This would require a huge capacitor and a
microstepping motor to turn the shaft. This would make a large and
cumbersome assembly.

I need to compare the phase of the WWVB signal with the GPS to analyze the
diurnal time shift affecting both signals. A GPS signal does not provide
phase information, so I need to use the 1 PPS signal and compare the time
with WWVB. A Ublox LEA-5T-0-003 50-channel 15ns 1pps Timing GPS module will
provide the 1 PPS:

https://www.ebay.com/itm/333297389966

The all I need is a way to offset the 10 MHz GPSDO clock to cancel the
dirurnal time shift of the GPS signal. Hopefully this will give better than
the typical 1e-12 error of the GPS.

Time-Nuts has numerous posts discussing the phase errors caused by resonant
circuits in the signal path, so I need a method of tuning the ferrite loop
and keeping it at resonance.

https://febo.com/pipermail/time-nuts_lists.febo.com/

Changing the capacitance is not feasible, so I am trying to find a way to
change the inductance. Hopefully, changing the permeability will do the
job.

Thanks for the help.

Jan Frank wrote:
================
>
> I am making a WWVB receiver to compare the diurnal phase shift with GPS.
>
> Ferrite loop antennas are available on Amazon, but they are fixed frequency
> and I need to find a way to tune them.
>

** Sliding the coil along the rod varies L .

AM radio 101

...... Phil

On 2021-12-18, Jan Frank <nospam@not.com> wrote:
> I am making a WWVB receiver to compare the diurnal phase shift with GPS.
>
> Ferrite loop antennas are available on Amazon, but they are fixed frequency
> and I need to find a way to tune them.
>
> I wonder if a magnetic field will affect the permeability so I can shift the
> frequency with a small magnet? It would be followed by a 60KHz xtal filter to
> narrow the bandwidth, so a reduction in Q is acceptable.
>
> The assembly would have to be in a temperature-controlled environment, but
> that's fairly easy.
>
> Any thoughts?

If it's too low grind some ferrite off. if it's too high glue some on

--
Jasen.

On 2021-12-19, Jasen Betts <usenet@revmaps.no-ip.org> wrote:
> On 2021-12-18, Jan Frank <nospam@not.com> wrote:
>> I am making a WWVB receiver to compare the diurnal phase shift with GPS.
>>
>> Ferrite loop antennas are available on Amazon, but they are fixed frequency
>> and I need to find a way to tune them.
>>
>> I wonder if a magnetic field will affect the permeability so I can shift the
>> frequency with a small magnet? It would be followed by a 60KHz xtal filter to
>> narrow the bandwidth, so a reduction in Q is acceptable.
>>
>> The assembly would have to be in a temperature-controlled environment, but
>> that's fairly easy.
>>
>> Any thoughts?
>
> If it's too low grind some ferrite off. if it's too high glue some on

or if you need a less permanent solution grind some off and then put a
movable chunk near one end of the antenna.

--
Jasen.

On a sunny day (Sat, 18 Dec 2021 13:10:35 -0800) it happened
jlarkin@highlandsniptechnology.com wrote in
<moesrg9rutdb92fjsnspiephm1536on38g@4ax.com>:

>On Sat, 18 Dec 2021 18:39:31 -0000 (UTC), Jan Frank <nospam@not.com>
>wrote:
>
>>I am making a WWVB receiver to compare the diurnal phase shift with GPS.
>>
>>Ferrite loop antennas are available on Amazon, but they are fixed frequency
>>and I need to find a way to tune them.
>>
>>I wonder if a magnetic field will affect the permeability so I can shift the
>>frequency with a small magnet? It would be followed by a 60KHz xtal filter to
>>narrow the bandwidth, so a reduction in Q is acceptable.
>>
>>The assembly would have to be in a temperature-controlled environment, but
>>that's fairly easy.
>>
>>Any thoughts?
>
>How about a giant loop antenna? Use multiconductor shielded cable.
>Lots of pickup area.
>
>Normally one would ground one end of the shield, but why not resonate
>the shield?

Normally one would buy a ferite rod, look up the permeabiliy
get a few hundred pF cap calculate L required for frequency,
then add that many turns to the rod.

If he has a rod with coil, measure L, calculate C required.

My Casio waveceptor watch has o.a. radio DCF77 reception to automatically set time,
the ferrite rod in it is minucule.
Always accurate to the second.

On a sunny day (Sun, 19 Dec 2021 05:14:04 -0000 (UTC)) it happened Jan Frank
<spamme@not.com> wrote in <XnsAE052628EBB7idtokenpost@144.76.35.252>:

>jlarkin@highlandsniptechnology.com wrote:
>
>> On Sat, 18 Dec 2021 18:39:31 -0000 (UTC), Jan Frank <nospam@not.com>
>> wrote:
>>
>>>I am making a WWVB receiver to compare the diurnal phase shift with GPS.
>>>
>>>Ferrite loop antennas are available on Amazon, but they are fixed
>>>frequency and I need to find a way to tune them.
>>>
>>>I wonder if a magnetic field will affect the permeability so I can shift
>>>the frequency with a small magnet? It would be followed by a 60KHz xtal
>>>filter to narrow the bandwidth, so a reduction in Q is acceptable.
>>>
>>>The assembly would have to be in a temperature-controlled environment,
>>>but that's fairly easy.
>>>
>>>Any thoughts?
>>
>> How about a giant loop antenna? Use multiconductor shielded cable.
>> Lots of pickup area.
>>
>> Normally one would ground one end of the shield, but why not resonate
>> the shield?
>
>Thanks for the suggestion, but I don't need a large pickup area. I have a
>number of WWVB clocks, including two Casio Waveceptor wrist watches. They
>have a tiny ferrite antenna to fit in the small case, but still have enough
>signal to synchronize perfectly every night:
>
>https://www.amazon.ca/s?k=casio+waveceptor+watches+men
>
>The Amazon ferrite loop is much larger and should provide plenty of signal:
>
>https://www.amazon.ca/gp/product/B01KH3VEGS/
>
>In addition there is no way to trim the resonance of a large loop except by
>changing the capacitor. This would require a huge capacitor and a
>microstepping motor to turn the shaft. This would make a large and
>cumbersome assembly.
>
>I need to compare the phase of the WWVB signal with the GPS to analyze the
>diurnal time shift affecting both signals. A GPS signal does not provide
>phase information, so I need to use the 1 PPS signal and compare the time
>with WWVB. A Ublox LEA-5T-0-003 50-channel 15ns 1pps Timing GPS module will
>provide the 1 PPS:
>
>https://www.ebay.com/itm/333297389966
>
>The all I need is a way to offset the 10 MHz GPSDO clock to cancel the
>dirurnal time shift of the GPS signal. Hopefully this will give better than
>the typical 1e-12 error of the GPS.
>
>Time-Nuts has numerous posts discussing the phase errors caused by resonant
>circuits in the signal path, so I need a method of tuning the ferrite loop
>and keeping it at resonance.
>
>https://febo.com/pipermail/time-nuts_lists.febo.com/
>
>Changing the capacitance is not feasible,

We have the same watch it seems.
Anyways large capacitance varicaps exist
(I have used those for very low frequencis)
or you could use some normal diode at low reverse bias for that.

On 18/12/2021 18:39, Jan Frank wrote:
> I am making a WWVB receiver to compare the diurnal phase shift with GPS.
>
> Ferrite loop antennas are available on Amazon, but they are fixed frequency
> and I need to find a way to tune them.

You can get pre tuned ferrite loop antennas. You won't need to tune them
they are more or less spot on 60kHz +/- small fractions of a ppm.
>
> I wonder if a magnetic field will affect the permeability so I can shift the
> frequency with a small magnet? It would be followed by a 60KHz xtal filter to
> narrow the bandwidth, so a reduction in Q is acceptable.
>
> The assembly would have to be in a temperature-controlled environment, but
> that's fairly easy.

You should look at the low frequency LBI studies by Duffet-Smith et al
in the 1980's. They were disciplining a local Rb clock with the MSF
Rugby signal so their local clock was way better frequency stability
than the instantaneous signal from Rugby.

ISTR What they found was that the time delays depended critically on the
air humidity and amount of dew on the ground at the transmitter site.
This is hardly surprising as it affects the time constant of their
transmitting antenna. MSF Rugby were interested in the result.

GPS is essentially a better than Rb clock so you should be able to
reproduce their results (They were doing it to timestamp interferometer
data in a not quite VLBI method at low frequencies).

Looking for the white light fringe in LBI is still a nightmare even when
you have precision timestamps - particularly with the hardware of that era.

This isn't the paper I remember but search terms into ADS elude me for
the moment. It is related but at 16kHz (submarine comms frequency).

https://ui.adsabs.harvard.edu/abs/1985RaF....28..574S/abstract

--
Regards,
Martin Brown

Martin Brown IDIOT and stinking LIAR wrote:
===================================
>
> > Ferrite loop antennas are available on Amazon, but they are fixed frequency
> > and I need to find a way to tune them.
>
> You can get pre tuned ferrite loop antennas. You won't need to tune them
> they are more or less spot on 60kHz +/- small fractions of a ppm.
>

** The OP has already posted a link to EXACTLY one of them.

Are YOU blind ??
You bullshitting, lying POS leftist cunt.

...... Phil

Martin Brown <'''newspam'''@nonad.co.uk> wrote:

> On 18/12/2021 18:39, Jan Frank wrote:
>> I am making a WWVB receiver to compare the diurnal phase shift with
>> GPS.
>>
>> Ferrite loop antennas are available on Amazon, but they are fixed
>> frequency and I need to find a way to tune them.
>
> You can get pre tuned ferrite loop antennas. You won't need to tune them
> they are more or less spot on 60kHz +/- small fractions of a ppm.
>>
>> I wonder if a magnetic field will affect the permeability so I can
>> shift the frequency with a small magnet? It would be followed by a
>> 60KHz xtal filter to narrow the bandwidth, so a reduction in Q is
>> acceptable.
>>
>> The assembly would have to be in a temperature-controlled environment,
>> but that's fairly easy.
>
> You should look at the low frequency LBI studies by Duffet-Smith et al
> in the 1980's. They were disciplining a local Rb clock with the MSF
> Rugby signal so their local clock was way better frequency stability
> than the instantaneous signal from Rugby.
>
> ISTR What they found was that the time delays depended critically on the
> air humidity and amount of dew on the ground at the transmitter site.
> This is hardly surprising as it affects the time constant of their
> transmitting antenna. MSF Rugby were interested in the result.
>
> GPS is essentially a better than Rb clock so you should be able to
> reproduce their results (They were doing it to timestamp interferometer
> data in a not quite VLBI method at low frequencies).
>
> Looking for the white light fringe in LBI is still a nightmare even when
> you have precision timestamps - particularly with the hardware of that
> era.
>
> This isn't the paper I remember but search terms into ADS elude me for
> the moment. It is related but at 16kHz (submarine comms frequency).
>
> https://ui.adsabs.harvard.edu/abs/1985RaF....28..574S/abstract

Thanks for the info. I am trying to cancel the diurnal time shift of GPS
signals by using phase information from WWVB signals to improve the typical
1e-12 accuracy of the GPS. Even 100e-15 would be a significant improvement.

I have a number of Rb clocks for use in a N-corner hat to compare the GPS
and WWVB signals. Ideally the reference should be a hydrogen maser but that
is far beyond most people's budgets. However, moving GPS closer would be a
valuable improvement at far lower cost.

Interesting comment about humidity. However, there are other signals in the
vlf region such as 100KHz that could also be used.

On 19/12/2021 13:40, Jan Frank wrote:
> Martin Brown <'''newspam'''@nonad.co.uk> wrote:
>
>> On 18/12/2021 18:39, Jan Frank wrote:
>>> I am making a WWVB receiver to compare the diurnal phase shift with
>>> GPS.
>>>
>>> Ferrite loop antennas are available on Amazon, but they are fixed
>>> frequency and I need to find a way to tune them.
>>
>> You can get pre tuned ferrite loop antennas. You won't need to tune them
>> they are more or less spot on 60kHz +/- small fractions of a ppm.
>>>
>>> I wonder if a magnetic field will affect the permeability so I can
>>> shift the frequency with a small magnet? It would be followed by a
>>> 60KHz xtal filter to narrow the bandwidth, so a reduction in Q is
>>> acceptable.
>>>
>>> The assembly would have to be in a temperature-controlled environment,
>>> but that's fairly easy.
>>
>> You should look at the low frequency LBI studies by Duffet-Smith et al
>> in the 1980's. They were disciplining a local Rb clock with the MSF
>> Rugby signal so their local clock was way better frequency stability
>> than the instantaneous signal from Rugby.
>>
>> ISTR What they found was that the time delays depended critically on the
>> air humidity and amount of dew on the ground at the transmitter site.
>> This is hardly surprising as it affects the time constant of their
>> transmitting antenna. MSF Rugby were interested in the result.
>>
>> GPS is essentially a better than Rb clock so you should be able to
>> reproduce their results (They were doing it to timestamp interferometer
>> data in a not quite VLBI method at low frequencies).
>>
>> Looking for the white light fringe in LBI is still a nightmare even when
>> you have precision timestamps - particularly with the hardware of that
>> era.
>>
>> This isn't the paper I remember but search terms into ADS elude me for
>> the moment. It is related but at 16kHz (submarine comms frequency).
>>
>> https://ui.adsabs.harvard.edu/abs/1985RaF....28..574S/abstract
>
> Thanks for the info. I am trying to cancel the diurnal time shift of GPS
> signals by using phase information from WWVB signals to improve the typical
> 1e-12 accuracy of the GPS. Even 100e-15 would be a significant improvement.
>
> I have a number of Rb clocks for use in a N-corner hat to compare the GPS
> and WWVB signals. Ideally the reference should be a hydrogen maser but that
> is far beyond most people's budgets. However, moving GPS closer would be a
> valuable improvement at far lower cost.

OK. If you have an Rb clock to hand you definitely want the paper that
describes the MRAO portable Rb clock synchronisation to MSF & Loran.
>
> Interesting comment about humidity. However, there are other signals in the
> vlf region such as 100KHz that could also be used.

If memory serves there was a systematic ~2us lag in the early morning
signal compared to light travel time to the remote site which went away
as the sun dried the ground.

Not mentioned in the only paper about it I can find at 81.5MHz but the
references may well include one with more details of the hardware.

https://articles.adsabs.harvard.edu/pdf/1983MNRAS.205..625H

VLBI these days invariably use H masers as local clocks.

--
Regards,
Martin Brown

On 18/12/2021 6:39 pm, Jan Frank wrote:
> I am making a WWVB receiver to compare the diurnal phase shift with GPS.
>
> Ferrite loop antennas are available on Amazon, but they are fixed frequency
> and I need to find a way to tune them.
>
> I wonder if a magnetic field will affect the permeability so I can shift the
> frequency with a small magnet? It would be followed by a 60KHz xtal filter to
> narrow the bandwidth, so a reduction in Q is acceptable.
>
> The assembly would have to be in a temperature-controlled environment, but
> that's fairly easy.
>
> Any thoughts?

Yes driving a variable direct current thru second coil around the
ferrite rod will decrease the permeability. If you set the unsaturated
system to resonant slightly low then you could adjust the dc bias to hit
resonance. BTW how to you plan to know when the loop is resonant?

I wonder since you are comparing against the 1PS GPS timekeeping can you
simply go by the 1PS WWVB time code instead of measuring WWVB carrier
frequency?

piglet

On Sun, 19 Dec 2021 05:14:04 -0000 (UTC), Jan Frank <spamme@not.com>
wrote:

>jlarkin@highlandsniptechnology.com wrote:
>
>> On Sat, 18 Dec 2021 18:39:31 -0000 (UTC), Jan Frank <nospam@not.com>
>> wrote:
>>
>>>I am making a WWVB receiver to compare the diurnal phase shift with GPS.
>>>
>>>Ferrite loop antennas are available on Amazon, but they are fixed
>>>frequency and I need to find a way to tune them.
>>>
>>>I wonder if a magnetic field will affect the permeability so I can shift
>>>the frequency with a small magnet? It would be followed by a 60KHz xtal
>>>filter to narrow the bandwidth, so a reduction in Q is acceptable.
>>>
>>>The assembly would have to be in a temperature-controlled environment,
>>>but that's fairly easy.
>>>
>>>Any thoughts?
>>
>> How about a giant loop antenna? Use multiconductor shielded cable.
>> Lots of pickup area.
>>
>> Normally one would ground one end of the shield, but why not resonate
>> the shield?
>
>Thanks for the suggestion, but I don't need a large pickup area. I have a
>number of WWVB clocks, including two Casio Waveceptor wrist watches. They
>have a tiny ferrite antenna to fit in the small case, but still have enough
>signal to synchronize perfectly every night:
>
>https://www.amazon.ca/s?k=casio+waveceptor+watches+men
>
>The Amazon ferrite loop is much larger and should provide plenty of signal:
>
>https://www.amazon.ca/gp/product/B01KH3VEGS/
>
>In addition there is no way to trim the resonance of a large loop except by
>changing the capacitor. This would require a huge capacitor and a
>microstepping motor to turn the shaft. This would make a large and
>cumbersome assembly.
>
>I need to compare the phase of the WWVB signal with the GPS to analyze the
>diurnal time shift affecting both signals. A GPS signal does not provide
>phase information, so I need to use the 1 PPS signal and compare the time
>with WWVB. A Ublox LEA-5T-0-003 50-channel 15ns 1pps Timing GPS module will
>provide the 1 PPS:
>
>https://www.ebay.com/itm/333297389966
>
>The all I need is a way to offset the 10 MHz GPSDO clock to cancel the
>dirurnal time shift of the GPS signal. Hopefully this will give better than
>the typical 1e-12 error of the GPS.
>
>Time-Nuts has numerous posts discussing the phase errors caused by resonant
>circuits in the signal path, so I need a method of tuning the ferrite loop
>and keeping it at resonance.
>
>https://febo.com/pipermail/time-nuts_lists.febo.com/
>
>Changing the capacitance is not feasible, so I am trying to find a way to
>change the inductance. Hopefully, changing the permeability will do the
>job.
>
>Thanks for the help.

At 60 KHz, 1 ns resolution is 0.02 degrees. I don't think a ferrite
rod antenna will be stable to numbers like that. A loop or solenoid
air-core antenna might.

Maybe a solenoid in an oven! With tuning/amplifiers as needed. May as
well put your GPS in the oven too. (I'm thinking ovens because we're
controlling some optical stuff to a few mK just now.)

https://www.dropbox.com/s/f6h8tfyq0xkqx1q/Oven_Cables_pub.jpg?raw=1

1 PPS doesn't provide much information. You could use a good GPS 10
MHz clock to sample the 60K waveform and average the heck out of that.
A cheap digital oscilloscope could digitize the 60K and 10M waveforms
for you, and you could math that. Channel-to-channel time drift is low
on most scopes, far better than trig-to-channel.

--

I yam what I yam - Popeye

On Sunday, December 19, 2021 at 1:14:10 AM UTC-4, Jan Frank wrote:
> jla...@highlandsniptechnology.com wrote:
>
> > On Sat, 18 Dec 2021 18:39:31 -0000 (UTC), Jan Frank <nos...@not.com>
> > wrote:
> >
> >>I am making a WWVB receiver to compare the diurnal phase shift with GPS..
> >>
> >>Ferrite loop antennas are available on Amazon, but they are fixed
> >>frequency and I need to find a way to tune them.
> >>
> >>I wonder if a magnetic field will affect the permeability so I can shift
> >>the frequency with a small magnet? It would be followed by a 60KHz xtal
> >>filter to narrow the bandwidth, so a reduction in Q is acceptable.
> >>
> >>The assembly would have to be in a temperature-controlled environment,
> >>but that's fairly easy.
> >>
> >>Any thoughts?
> >
> > How about a giant loop antenna? Use multiconductor shielded cable.
> > Lots of pickup area.
> >
> > Normally one would ground one end of the shield, but why not resonate
> > the shield?
> Thanks for the suggestion, but I don't need a large pickup area. I have a
> number of WWVB clocks, including two Casio Waveceptor wrist watches. They
> have a tiny ferrite antenna to fit in the small case, but still have enough
> signal to synchronize perfectly every night:
>
> https://www.amazon.ca/s?k=casio+waveceptor+watches+men
>
> The Amazon ferrite loop is much larger and should provide plenty of signal:
>
> https://www.amazon.ca/gp/product/B01KH3VEGS/
>
> In addition there is no way to trim the resonance of a large loop except by
> changing the capacitor. This would require a huge capacitor and a
> microstepping motor to turn the shaft. This would make a large and
> cumbersome assembly.
>
> I need to compare the phase of the WWVB signal with the GPS to analyze the
> diurnal time shift affecting both signals. A GPS signal does not provide
> phase information, so I need to use the 1 PPS signal and compare the time
> with WWVB. A Ublox LEA-5T-0-003 50-channel 15ns 1pps Timing GPS module will
> provide the 1 PPS:
>
> https://www.ebay.com/itm/333297389966
>
> The all I need is a way to offset the 10 MHz GPSDO clock to cancel the
> dirurnal time shift of the GPS signal. Hopefully this will give better than
> the typical 1e-12 error of the GPS.
>
> Time-Nuts has numerous posts discussing the phase errors caused by resonant
> circuits in the signal path, so I need a method of tuning the ferrite loop
> and keeping it at resonance.
>
> https://febo.com/pipermail/time-nuts_lists.febo.com/
>
> Changing the capacitance is not feasible, so I am trying to find a way to
> change the inductance. Hopefully, changing the permeability will do the
> job.

There are diodes specifically designed for capacitance tuning. Although they are largely obsolete and hard to find, they still available. I don't recall the capacitance required to tune a ferrite loop to 60 kHz, but some hundreds of pF should suffice for fine tuning. No? I think the trick would be dealing with the temperature characteristic of the fixed capacitor already installed, but I think you said you would control the temperature. Even so, you might want to replace that with your own capacitor with a more stable temperature coefficient.

So is this feasible or am I missing something?

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

On Sunday, 19 December 2021 at 17:55:25 UTC, gnuarm.del...@gmail.com wrote:
> On Sunday, December 19, 2021 at 1:14:10 AM UTC-4, Jan Frank wrote:
> > jla...@highlandsniptechnology.com wrote:
> >
> > > On Sat, 18 Dec 2021 18:39:31 -0000 (UTC), Jan Frank <nos...@not.com>
> > > wrote:
> > >
> > >>I am making a WWVB receiver to compare the diurnal phase shift with GPS.
> > >>
> > >>Ferrite loop antennas are available on Amazon, but they are fixed
> > >>frequency and I need to find a way to tune them.
> > >>
> > >>I wonder if a magnetic field will affect the permeability so I can shift
> > >>the frequency with a small magnet? It would be followed by a 60KHz xtal
> > >>filter to narrow the bandwidth, so a reduction in Q is acceptable.
> > >>
> > >>The assembly would have to be in a temperature-controlled environment,
> > >>but that's fairly easy.
> > >>
> > >>Any thoughts?
> > >
> > > How about a giant loop antenna? Use multiconductor shielded cable.
> > > Lots of pickup area.
> > >
> > > Normally one would ground one end of the shield, but why not resonate
> > > the shield?
> > Thanks for the suggestion, but I don't need a large pickup area. I have a
> > number of WWVB clocks, including two Casio Waveceptor wrist watches. They
> > have a tiny ferrite antenna to fit in the small case, but still have enough
> > signal to synchronize perfectly every night:
> >
> > https://www.amazon.ca/s?k=casio+waveceptor+watches+men
> >
> > The Amazon ferrite loop is much larger and should provide plenty of signal:
> >
> > https://www.amazon.ca/gp/product/B01KH3VEGS/
> >
> > In addition there is no way to trim the resonance of a large loop except by
> > changing the capacitor. This would require a huge capacitor and a
> > microstepping motor to turn the shaft. This would make a large and
> > cumbersome assembly.
> >
> > I need to compare the phase of the WWVB signal with the GPS to analyze the
> > diurnal time shift affecting both signals. A GPS signal does not provide
> > phase information, so I need to use the 1 PPS signal and compare the time
> > with WWVB. A Ublox LEA-5T-0-003 50-channel 15ns 1pps Timing GPS module will
> > provide the 1 PPS:
> >
> > https://www.ebay.com/itm/333297389966
> >
> > The all I need is a way to offset the 10 MHz GPSDO clock to cancel the
> > dirurnal time shift of the GPS signal. Hopefully this will give better than
> > the typical 1e-12 error of the GPS.
> >
> > Time-Nuts has numerous posts discussing the phase errors caused by resonant
> > circuits in the signal path, so I need a method of tuning the ferrite loop
> > and keeping it at resonance.
> >
> > https://febo.com/pipermail/time-nuts_lists.febo.com/
> >
> > Changing the capacitance is not feasible, so I am trying to find a way to
> > change the inductance. Hopefully, changing the permeability will do the
> > job.
> There are diodes specifically designed for capacitance tuning. Although they are largely obsolete and hard to find, they still available. I don't recall the capacitance required to tune a ferrite loop to 60 kHz, but some hundreds of pF should suffice for fine tuning. No? I think the trick would be dealing with the temperature characteristic of the fixed capacitor already installed, but I think you said you would control the temperature. Even so, you might want to replace that with your own capacitor with a more stable temperature coefficient.
>
> So is this feasible or am I missing something?
>
> --
>
> Rick C.
>
> - Get 1,000 miles of free Supercharging
> - Tesla referral code - https://ts.la/richard11209

Why does the ferrite rod need to be highly tuned if there is plenty of signal?
An alternative approach might be to use a broadly tuned ferrite antenna
with just enough selectivity to avoid overloading subsequent stages
with other signals and then digitise the 60kHz WWVB signal with a
wide-band 24-bit audio ADC, perhaps sampling at around 192ksa/s.
This would be fine for acquiring a 60kHz signal. You could then process
the ADC output with a linear-phase digital filter to get the final selectivity
you need.
John

On Sun, 19 Dec 2021 07:39:10 GMT, Jan Panteltje
<pNaOnStPeAlMtje@yahoo.com> wrote:

>On a sunny day (Sun, 19 Dec 2021 05:14:04 -0000 (UTC)) it happened Jan Frank
><spamme@not.com> wrote in <XnsAE052628EBB7idtokenpost@144.76.35.252>:
>
>>jlarkin@highlandsniptechnology.com wrote:
>>
>>> On Sat, 18 Dec 2021 18:39:31 -0000 (UTC), Jan Frank <nospam@not.com>
>>> wrote:
>>>
>>>>I am making a WWVB receiver to compare the diurnal phase shift with GPS.
>>>>
>>>>Ferrite loop antennas are available on Amazon, but they are fixed
>>>>frequency and I need to find a way to tune them.
>>>>
>>>>I wonder if a magnetic field will affect the permeability so I can shift
>>>>the frequency with a small magnet? It would be followed by a 60KHz xtal
>>>>filter to narrow the bandwidth, so a reduction in Q is acceptable.
>>>>
>>>>The assembly would have to be in a temperature-controlled environment,
>>>>but that's fairly easy.
>>>>
>>>>Any thoughts?
>>>
>>> How about a giant loop antenna? Use multiconductor shielded cable.
>>> Lots of pickup area.
>>>
>>> Normally one would ground one end of the shield, but why not resonate
>>> the shield?
>>
>>Thanks for the suggestion, but I don't need a large pickup area. I have a
>>number of WWVB clocks, including two Casio Waveceptor wrist watches. They
>>have a tiny ferrite antenna to fit in the small case, but still have enough
>>signal to synchronize perfectly every night:
>>
>>https://www.amazon.ca/s?k=casio+waveceptor+watches+men
>>
>>The Amazon ferrite loop is much larger and should provide plenty of signal:
>>
>>https://www.amazon.ca/gp/product/B01KH3VEGS/
>>
>>In addition there is no way to trim the resonance of a large loop except by
>>changing the capacitor. This would require a huge capacitor and a
>>microstepping motor to turn the shaft. This would make a large and
>>cumbersome assembly.
>>
>>I need to compare the phase of the WWVB signal with the GPS to analyze the
>>diurnal time shift affecting both signals. A GPS signal does not provide
>>phase information, so I need to use the 1 PPS signal and compare the time
>>with WWVB. A Ublox LEA-5T-0-003 50-channel 15ns 1pps Timing GPS module will
>>provide the 1 PPS:
>>
>>https://www.ebay.com/itm/333297389966
>>
>>The all I need is a way to offset the 10 MHz GPSDO clock to cancel the
>>dirurnal time shift of the GPS signal. Hopefully this will give better than
>>the typical 1e-12 error of the GPS.
>>
>>Time-Nuts has numerous posts discussing the phase errors caused by resonant
>>circuits in the signal path, so I need a method of tuning the ferrite loop
>>and keeping it at resonance.
>>
>>https://febo.com/pipermail/time-nuts_lists.febo.com/
>>
>>Changing the capacitance is not feasible,
>
>We have the same watch it seems.
>Anyways large capacitance varicaps exist
>(I have used those for very low frequencis)
>or you could use some normal diode at low reverse bias for that.

Varicaps have ghastly tempcos that change with bias.

I think Jan is looking for high time resolution, nanoseconds maybe, so
varicaps and ferrites are out of the game.

If he's looking for a diurnal time shift, that could be overwhelmmed
by the diurnal temperature cycle whacking all the gear.

--

I yam what I yam - Popeye

On Sunday, December 19, 2021 at 10:38:37 AM UTC-4, erichp...@hotmail.com wrote:
> On 18/12/2021 6:39 pm, Jan Frank wrote:
> > I am making a WWVB receiver to compare the diurnal phase shift with GPS..
> >
> > Ferrite loop antennas are available on Amazon, but they are fixed frequency
> > and I need to find a way to tune them.
> >
> > I wonder if a magnetic field will affect the permeability so I can shift the
> > frequency with a small magnet? It would be followed by a 60KHz xtal filter to
> > narrow the bandwidth, so a reduction in Q is acceptable.
> >
> > The assembly would have to be in a temperature-controlled environment, but
> > that's fairly easy.
> >
> > Any thoughts?
> Yes driving a variable direct current thru second coil around the
> ferrite rod will decrease the permeability. If you set the unsaturated
> system to resonant slightly low then you could adjust the dc bias to hit
> resonance. BTW how to you plan to know when the loop is resonant?
>
> I wonder since you are comparing against the 1PS GPS timekeeping can you
> simply go by the 1PS WWVB time code instead of measuring WWVB carrier
> frequency?

That is a point. Although you get 60,000 times more points to average with the carrier phase. In the end the detail that is being used for timing with the modulation are the edges of the modulation changes. These will be nowhere near as precise as the carrier phase due to the bandwidth limitations of the transmitter and receiver and even possibly the atmospheric conditions.

If you don't care about the absolute time, but only relative changes, I think measuring carrier phase is the way to go.

It may well be the GPS side that is limiting. The 1 PPS signal is often specified with a significant jitter, probably a result of being produced in a clocked digital system. The 17 us carrier is three orders of magnitude from the GPS digital jitter that may be 20 ns to 50 ns, so it will require a great deal of averaging of both the GPS and the WWVB signals to improve on that precision.

I wonder if it would be just as effective and perhaps easier to implement a disciplined local oscillator that simply references the GPS signal? The characteristic of the WWVB signal that is being used is the *average* accuracy. I'm sure the GPS signal has this same property, so in reality the WWVB signal is redundant. In fact, the GPS signal probably has superior short term stability, but the generation of the 1 PPS signal mitigates that. Other frequency signals can also be emitted by most GPS devices, 1 kHz, 10 kHz, etc. They will have the same jitter spec most likely, but provide more points to average over.

What am I missing about using WWVB to discipline a local oscillator that would make it better than the GPS disciplined local oscillator? One downside is that WWVB is *not* a strong signal in many locations so that it is not available during the day.

What is being measured are the temporary deviations in the GPS signal which can be just as well compared to the *average* GPS timing rather than to an external reference.

--

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209

On Sat, 18 Dec 2021 18:39:31 -0000 (UTC), Jan Frank <nospam@not.com>
wrote:

>I am making a WWVB receiver to compare the diurnal phase shift with GPS.
>
>Ferrite loop antennas are available on Amazon, but they are fixed frequency
>and I need to find a way to tune them.
>
>I wonder if a magnetic field will affect the permeability so I can shift the
>frequency with a small magnet? It would be followed by a 60KHz xtal filter to
>narrow the bandwidth, so a reduction in Q is acceptable.
>
>The assembly would have to be in a temperature-controlled environment, but
>that's fairly easy.
>
>Any thoughts?

What phase shift do you want to measure, the GPS or the WWVB?

You can get a cheap surplus rubidium standard that will drift
nanoseconds per day. That could be the reference that you measure the
other against.

It's fun to trigger a scope from one rubidium and zoom the rising edge
from another at ns per division. It looks internally triggered! Check
it occasionally and see it creep across the screen.

--

I yam what I yam - Popeye

On Sunday, December 19, 2021 at 2:46:54 PM UTC-4, John Walliker wrote:
> On Sunday, 19 December 2021 at 17:55:25 UTC, gnuarm.del...@gmail.com wrote:
> > There are diodes specifically designed for capacitance tuning. Although they are largely obsolete and hard to find, they still available. I don't recall the capacitance required to tune a ferrite loop to 60 kHz, but some hundreds of pF should suffice for fine tuning. No? I think the trick would be dealing with the temperature characteristic of the fixed capacitor already installed, but I think you said you would control the temperature. Even so, you might want to replace that with your own capacitor with a more stable temperature coefficient.
> >
> > So is this feasible or am I missing something?
> >
> >
> > - Get 1,000 miles of free Supercharging
> > - Tesla referral code - https://ts.la/richard11209
> Why does the ferrite rod need to be highly tuned if there is plenty of signal?
> An alternative approach might be to use a broadly tuned ferrite antenna
> with just enough selectivity to avoid overloading subsequent stages
> with other signals and then digitise the 60kHz WWVB signal with a
> wide-band 24-bit audio ADC, perhaps sampling at around 192ksa/s.
> This would be fine for acquiring a 60kHz signal. You could then process
> the ADC output with a linear-phase digital filter to get the final selectivity
> you need.

The ferrite rod needs to be highly tuned because unless you are very close to the transmitter, the signal gets swamped by extraneous interferers. The tuning is actually how a loop antenna works. The effective height of a typical small loop antenna is small, but is multiplied by the Q to determine the output voltage. It is the high Q that makes a sensitive loop.

Even with the high Q of a tuned loop antenna additional filtering is important as interferers are often strong.

--

Rick C.

-- Get 1,000 miles of free Supercharging
-- Tesla referral code - https://ts.la/richard11209

On Sunday, December 19, 2021 at 3:38:49 PM UTC-4, jla...@highlandsniptechnology.com wrote:
> On Sun, 19 Dec 2021 07:39:10 GMT, Jan Panteltje
> <pNaOnSt...@yahoo.com> wrote:
>
> >On a sunny day (Sun, 19 Dec 2021 05:14:04 -0000 (UTC)) it happened Jan Frank
> ><spa...@not.com> wrote in <XnsAE052628EB...@144.76.35.252>:
> >
> >>jla...@highlandsniptechnology.com wrote:
> >>
> >>> On Sat, 18 Dec 2021 18:39:31 -0000 (UTC), Jan Frank <nos...@not.com>
> >>> wrote:
> >>>
> >>>>I am making a WWVB receiver to compare the diurnal phase shift with GPS.
> >>>>
> >>>>Ferrite loop antennas are available on Amazon, but they are fixed
> >>>>frequency and I need to find a way to tune them.
> >>>>
> >>>>I wonder if a magnetic field will affect the permeability so I can shift
> >>>>the frequency with a small magnet? It would be followed by a 60KHz xtal
> >>>>filter to narrow the bandwidth, so a reduction in Q is acceptable.
> >>>>
> >>>>The assembly would have to be in a temperature-controlled environment,
> >>>>but that's fairly easy.
> >>>>
> >>>>Any thoughts?
> >>>
> >>> How about a giant loop antenna? Use multiconductor shielded cable.
> >>> Lots of pickup area.
> >>>
> >>> Normally one would ground one end of the shield, but why not resonate
> >>> the shield?
> >>
> >>Thanks for the suggestion, but I don't need a large pickup area. I have a
> >>number of WWVB clocks, including two Casio Waveceptor wrist watches. They
> >>have a tiny ferrite antenna to fit in the small case, but still have enough
> >>signal to synchronize perfectly every night:
> >>
> >>https://www.amazon.ca/s?k=casio+waveceptor+watches+men
> >>
> >>The Amazon ferrite loop is much larger and should provide plenty of signal:
> >>
> >>https://www.amazon.ca/gp/product/B01KH3VEGS/
> >>
> >>In addition there is no way to trim the resonance of a large loop except by
> >>changing the capacitor. This would require a huge capacitor and a
> >>microstepping motor to turn the shaft. This would make a large and
> >>cumbersome assembly.
> >>
> >>I need to compare the phase of the WWVB signal with the GPS to analyze the
> >>diurnal time shift affecting both signals. A GPS signal does not provide
> >>phase information, so I need to use the 1 PPS signal and compare the time
> >>with WWVB. A Ublox LEA-5T-0-003 50-channel 15ns 1pps Timing GPS module will
> >>provide the 1 PPS:
> >>
> >>https://www.ebay.com/itm/333297389966
> >>
> >>The all I need is a way to offset the 10 MHz GPSDO clock to cancel the
> >>dirurnal time shift of the GPS signal. Hopefully this will give better than
> >>the typical 1e-12 error of the GPS.
> >>
> >>Time-Nuts has numerous posts discussing the phase errors caused by resonant
> >>circuits in the signal path, so I need a method of tuning the ferrite loop
> >>and keeping it at resonance.
> >>
> >>https://febo.com/pipermail/time-nuts_lists.febo.com/
> >>
> >>Changing the capacitance is not feasible,
> >
> >We have the same watch it seems.
> >Anyways large capacitance varicaps exist
> >(I have used those for very low frequencis)
> >or you could use some normal diode at low reverse bias for that.
> Varicaps have ghastly tempcos that change with bias.
>
> I think Jan is looking for high time resolution, nanoseconds maybe, so
> varicaps and ferrites are out of the game.
>
> If he's looking for a diurnal time shift, that could be overwhelmmed
> by the diurnal temperature cycle whacking all the gear.

The ferrite or capacitance adjustment is to mitigate a source of error in the measurement. It may be within the project's error budget to have some error in the error compensation, a secondary impact on the measurement itself. We can only know what is an acceptable solution if we had detailed requirements. So we brainstorm and propose ideas that may well work depending on the details such as the quality of the temperature stabilization.

With temperature control of the electronics, this could provide a very stable reference.

--

Rick C.

-+ Get 1,000 miles of free Supercharging
-+ Tesla referral code - https://ts.la/richard11209

piglet <erichpwagner@hotmail.com> wrote:

> On 18/12/2021 6:39 pm, Jan Frank wrote:
>> I am making a WWVB receiver to compare the diurnal phase shift with
>> GPS.
>>
>> Ferrite loop antennas are available on Amazon, but they are fixed
>> frequency and I need to find a way to tune them.
>>
>> I wonder if a magnetic field will affect the permeability so I can
>> shift the frequency with a small magnet? It would be followed by a
>> 60KHz xtal filter to narrow the bandwidth, so a reduction in Q is
>> acceptable.
>>
>> The assembly would have to be in a temperature-controlled environment,
>> but that's fairly easy.
>>
>> Any thoughts?
>
> Yes driving a variable direct current thru second coil around the
> ferrite rod will decrease the permeability. If you set the unsaturated
> system to resonant slightly low then you could adjust the dc bias to hit
> resonance. BTW how to you plan to know when the loop is resonant?
>
> I wonder since you are comparing against the 1PS GPS timekeeping can you
> simply go by the 1PS WWVB time code instead of measuring WWVB carrier
> frequency?
>
> piglet

Thanks for the info on permeability.

I need to compare the WWVB carrier phase against the GPS time signal. The
time code must be decoded which takes too long.

jlarkin@highlandsniptechnology.com wrote:

> On Sat, 18 Dec 2021 18:39:31 -0000 (UTC), Jan Frank <nospam@not.com>
> wrote:

[...]
> What phase shift do you want to measure, the GPS or the WWVB?
>
> You can get a cheap surplus rubidium standard that will drift
> nanoseconds per day. That could be the reference that you measure the
> other against.
>
> It's fun to trigger a scope from one rubidium and zoom the rising edge
> from another at ns per division. It looks internally triggered! Check
> it occasionally and see it creep across the screen.

I want to compare the WWVB carrier phase against the GPS 1 pps time signal.

I have a number of Rb's to use in a N-corner hat to analyze the results. The
goal is to see if offsetting the GPS 1 pps by changes in the WWVB carrier
would help reduce the diurnal shift in GPS time. This could improve the
typical GPS accuracy from 1e-12 to possibly 0.1e-12.

Martin Brown <'''newspam'''@nonad.co.uk> wrote:

> On 19/12/2021 13:40, Jan Frank wrote:
>> Martin Brown <'''newspam'''@nonad.co.uk> wrote:
>>
>>> On 18/12/2021 18:39, Jan Frank wrote:
>>>> I am making a WWVB receiver to compare the diurnal phase shift with
>>>> GPS.
>>>>
>>>> Ferrite loop antennas are available on Amazon, but they are fixed
>>>> frequency and I need to find a way to tune them.
>>>
>>> You can get pre tuned ferrite loop antennas. You won't need to tune
>>> them they are more or less spot on 60kHz +/- small fractions of a ppm.
>>>>
>>>> I wonder if a magnetic field will affect the permeability so I can
>>>> shift the frequency with a small magnet? It would be followed by a
>>>> 60KHz xtal filter to narrow the bandwidth, so a reduction in Q is
>>>> acceptable.
>>>>
>>>> The assembly would have to be in a temperature-controlled
>>>> environment, but that's fairly easy.
>>>
>>> You should look at the low frequency LBI studies by Duffet-Smith et al
>>> in the 1980's. They were disciplining a local Rb clock with the MSF
>>> Rugby signal so their local clock was way better frequency stability
>>> than the instantaneous signal from Rugby.
>>>
>>> ISTR What they found was that the time delays depended critically on
>>> the air humidity and amount of dew on the ground at the transmitter
>>> site. This is hardly surprising as it affects the time constant of
>>> their transmitting antenna. MSF Rugby were interested in the result.
>>>
>>> GPS is essentially a better than Rb clock so you should be able to
>>> reproduce their results (They were doing it to timestamp
>>> interferometer data in a not quite VLBI method at low frequencies).
>>>
>>> Looking for the white light fringe in LBI is still a nightmare even
>>> when you have precision timestamps - particularly with the hardware of
>>> that era.
>>>
>>> This isn't the paper I remember but search terms into ADS elude me for
>>> the moment. It is related but at 16kHz (submarine comms frequency).
>>>
>>> https://ui.adsabs.harvard.edu/abs/1985RaF....28..574S/abstract
>>
>> Thanks for the info. I am trying to cancel the diurnal time shift of
>> GPS signals by using phase information from WWVB signals to improve the
>> typical 1e-12 accuracy of the GPS. Even 100e-15 would be a significant
>> improvement.
>>
>> I have a number of Rb clocks for use in a N-corner hat to compare the
>> GPS and WWVB signals. Ideally the reference should be a hydrogen maser
>> but that is far beyond most people's budgets. However, moving GPS
>> closer would be a valuable improvement at far lower cost.
>
> OK. If you have an Rb clock to hand you definitely want the paper that
> describes the MRAO portable Rb clock synchronisation to MSF & Loran.
>>
>> Interesting comment about humidity. However, there are other signals in
>> the vlf region such as 100KHz that could also be used.
>
> If memory serves there was a systematic ~2us lag in the early morning
> signal compared to light travel time to the remote site which went away
> as the sun dried the ground.
>
> Not mentioned in the only paper about it I can find at 81.5MHz but the
> references may well include one with more details of the hardware.
>
> https://articles.adsabs.harvard.edu/pdf/1983MNRAS.205..625H
>
> VLBI these days invariably use H masers as local clocks.

Thanks for the paper.