Re: [time-nuts] WWV 25 MHz antenna switched to circular polarization

[Bob kb8tq]

Hi

Not in the least bit uncommon propagation at those frequencies and this time
of year.

Bob

> On Jul 16, 2017, at 8:44 PM, Clay Autery  wrote:
> 
> Prop shifted...  I tuned to it before I left for Home Depot at 1600 hrs
> CST, and it was strong  It was GONE by 1830 hrs.
> 
> __
> Clay Autery, KY5G
> MONTAC Enterprises
> (318) 518-1389
> 
> On 7/16/2017 6:32 PM, paul swed wrote:
>> Not hearing wwv on 25 MHz but 15 is fine. Using a beam and r1051 receiver.
>> Maybe its not on for the weekend. Its a 2 KW signal so should be able to
>> hear something.
>> Regards
>> Paul
>> WB8TSL
>> 
>> 
> 
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Re: [time-nuts] WWV 25 MHz antenna switched to circular polarization

[Magnus Danielson]

Solar wind conditions is such that right now things is flakey.

Cheers,
Magnus (at 1400 m in Lichtenstein on a mini DX expedition - we had to 
give up for the night)


On 07/17/2017 02:44 AM, Clay Autery wrote:

Prop shifted...  I tuned to it before I left for Home Depot at 1600 hrs
CST, and it was strong  It was GONE by 1830 hrs.

__
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389

On 7/16/2017 6:32 PM, paul swed wrote:

Not hearing wwv on 25 MHz but 15 is fine. Using a beam and r1051 receiver.
Maybe its not on for the weekend. Its a 2 KW signal so should be able to
hear something.
Regards
Paul
WB8TSL




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Re: [time-nuts] DAC performance [WAS: Papers on timing for lunar laser ranging]

[Bob kb8tq]

HI

This is a limitation on an OCXO based GPSDO. That’s really the bottom line 
here. 
It’s a limitation in an OCXO based part, but not in one based on an Rb or a Cs. 
If
the added component costs far more than a Cs, it’s not an answer. 

Bob

> On Jul 16, 2017, at 7:25 PM, Chris Albertson  
> wrote:
> 
> What about josephson standards?   After all, this is "Time Nuts" and we are
> allowed to propose silly-complex solutions to simple problems if it
> improves performance even a little.
> 
> But seriously I thought the issue of making a perfect voltage standard was
> solved because the Volt is defined to be whatever the Josephson array
> produces. Yes expensive because to runs at nearly absolute zero.
> 
> On Sun, Jul 16, 2017 at 4:10 PM, Bob kb8tq  wrote:
> 
>> Hi
>> 
>>> On Jul 16, 2017, at 6:33 PM, Richard (Rick) Karlquist <
>> rich...@karlquist.com> wrote:
>>> 
>>> 
>>> 
>>> On 7/16/2017 1:51 PM, Bob kb8tq wrote:
 Hi
 One gotcha with any ADC or DAC is going to be the reference. There, you
>> are in the same
 “get what you pay for” dilemma. Stable and noisy, can do. Quiet and not
>> very stable, can do.
 Both stable and quiet, not so easy if you want it cheap.
 Noise can also be the sigma delta ADC’s weak point. Even at slow rates,
>> some of them need
 a lot of averages to quiet down.
>>> 
>>> The reference initially used in the E1938A turned out to be too
>> noisy/unstable.  It was non trivial to find an upgrade.  The
>>> HP Smart Clocks of 20 years ago were limited in their performance
>>> by the reference used.
>>> 
>>> Has there been much improvement in references in the intervening
>>> 20 years?
>> 
>> They still don’t seem to have the hysteresis problem licked. Yes, you can
>> do an oversized reference
>> and take care of the issue. More or less that’s what you would have done
>> 20 years ago.
>> 
>> Bob
>> 
>> 
>>> 
>>> Rick N6RK
>> 
>> ___
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>> mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
> 
> 
> 
> -- 
> 
> Chris Albertson
> Redondo Beach, California
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Re: [time-nuts] WWV 25 MHz antenna switched to circular polarization

[Clay Autery]

Prop shifted...  I tuned to it before I left for Home Depot at 1600 hrs
CST, and it was strong  It was GONE by 1830 hrs.

__
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389

On 7/16/2017 6:32 PM, paul swed wrote:
> Not hearing wwv on 25 MHz but 15 is fine. Using a beam and r1051 receiver.
> Maybe its not on for the weekend. Its a 2 KW signal so should be able to
> hear something.
> Regards
> Paul
> WB8TSL
>
>

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Re: [time-nuts] DAC performance [WAS: Papers on timing for lunar laser ranging]

[Chris Albertson]

What about josephson standards?   After all, this is "Time Nuts" and we are
allowed to propose silly-complex solutions to simple problems if it
improves performance even a little.

But seriously I thought the issue of making a perfect voltage standard was
solved because the Volt is defined to be whatever the Josephson array
produces. Yes expensive because to runs at nearly absolute zero.

On Sun, Jul 16, 2017 at 4:10 PM, Bob kb8tq  wrote:

> Hi
>
> > On Jul 16, 2017, at 6:33 PM, Richard (Rick) Karlquist <
> rich...@karlquist.com> wrote:
> >
> >
> >
> > On 7/16/2017 1:51 PM, Bob kb8tq wrote:
> >> Hi
> >> One gotcha with any ADC or DAC is going to be the reference. There, you
> are in the same
> >> “get what you pay for” dilemma. Stable and noisy, can do. Quiet and not
> very stable, can do.
> >> Both stable and quiet, not so easy if you want it cheap.
> >> Noise can also be the sigma delta ADC’s weak point. Even at slow rates,
> some of them need
> >> a lot of averages to quiet down.
> >
> > The reference initially used in the E1938A turned out to be too
> noisy/unstable.  It was non trivial to find an upgrade.  The
> > HP Smart Clocks of 20 years ago were limited in their performance
> > by the reference used.
> >
> > Has there been much improvement in references in the intervening
> > 20 years?
>
> They still don’t seem to have the hysteresis problem licked. Yes, you can
> do an oversized reference
> and take care of the issue. More or less that’s what you would have done
> 20 years ago.
>
> Bob
>
>
> >
> > Rick N6RK
>
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>



-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] WWV 25 MHz antenna switched to circular polarization

[Don Murray via time-nuts]

FYI...
 
I was hearing WWV/25 several weeks ago peaking
S8 here in Central Texas...  WWV/20 was inaudible!  ;-)
 
Path 155 degrees 795 miles... 
 
Below from the NIST.gov Web Page: 
 
As of 2042 UTC 7 July 2017 the 25 MHz broadcast is now on a turnstile antenna 
with circular polarization and will remain in this configuration until after 
the solar eclipse on 21 Aug 2017.  Signal reports are requested.
 
 
 
73
Don
W4WJ
 
In a message dated 7/14/2017 12:47:12 PM Central Standard Time, 
paulsw...@gmail.com writes:

 
Gregory,I have to be honest and say I didn't even think wwv was on 25 MHz 
anymore.Son of a gun. I will have to listen.PaulWB8TSLOn Fri, Jul 14, 2017 at 
1:14 PM, Gregory Beat  wrote:> As reported by ARRL, a few days 
ago, on July 7th the 25 MHz antenna for> WWV was changed to circular 
polarization.> http://www.arrl.org/news/wwv-25-mhz-signal-swapped-to-> 
circular-polarization>> Matt Deutch, N0RGT the Lead electrical engineer at WWV 
said it’s hoped> that the latest antenna change to circular polarization might 
be helpful to> anyone studying radio propagation (ionosphere) during next 
month’s total> solar eclipse (August 21, 2017), which will be visible across 
the US.> “My effort right now is focused on getting the word out, just to make> 
people are aware that [the 25-MHz signal] is available, if it can be useful> to 
them.”>> greg, w9gb> Sent from iPad Air> 
___> time-nuts mailing list -- 
time-nuts@febo.com> To unsubscrib
 e, go to https://www.febo.com/cgi-bin/> mailman/listinfo/time-nuts> and follow 
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Re: [time-nuts] WWV 25 MHz antenna switched to circular polarization

[Christopher Hoover]

On Jul 16, 2017 4:49 PM, "Brian, WA1ZMS"  wrote:

FWIW.We're at an 11 yr low for solar activity. Thus no big suprise that
25MHz is not covering the US very well, but a rare opening is always
possible.


+1 de ai6kg
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Re: [time-nuts] WWV 25 MHz antenna switched to circular polarization

[Brian, WA1ZMS]

FWIW.We're at an 11 yr low for solar activity. Thus no big suprise that 
25MHz is not covering the US very well, but a rare opening is always possible.

-Brian
> On Jul 16, 2017, at 7:32 PM, paul swed  wrote:
> 
> Not hearing wwv on 25 MHz but 15 is fine. Using a beam and r1051 receiver.
> Maybe its not on for the weekend. Its a 2 KW signal so should be able to
> hear something.
> Regards
> Paul
> WB8TSL
> 
>> On Fri, Jul 14, 2017 at 9:29 PM, paul swed  wrote:
>> 
>> Sorry its a bit lower in the site that they resumed broadcasting.
>> I thought it had been off for many years. Amazing that they kept the
>> transmitter in shape for operation.
>> Regards
>> Paul
>> WB8TSL
>> 
>>> On Fri, Jul 14, 2017 at 9:27 PM, paul swed  wrote:
>>> 
>>> I went to the wwv site and do not see 25 MHz mentioned. I do see 20 MHz.
>>> 
 On Fri, Jul 14, 2017 at 1:17 PM, paul swed  wrote:
 
 Gregory,
 I have to be honest and say I didn't even think wwv was on 25 MHz
 anymore.
 Son of a gun. I will have to listen.
 Paul
 WB8TSL
 
> On Fri, Jul 14, 2017 at 1:14 PM, Gregory Beat  wrote:
> 
> As reported by ARRL, a few days ago, on July 7th the 25 MHz antenna for
> WWV was changed to circular polarization.
> http://www.arrl.org/news/wwv-25-mhz-signal-swapped-to-circul
> ar-polarization
> 
> Matt Deutch, N0RGT the Lead electrical engineer at WWV said it’s hoped
> that the latest antenna change to circular polarization might be helpful 
> to
> anyone studying radio propagation (ionosphere) during next month’s total
> solar eclipse (August 21, 2017), which will be visible across the US.

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Re: [time-nuts] WWV 25 MHz antenna switched to circular polarization

[paul swed]

Not hearing wwv on 25 MHz but 15 is fine. Using a beam and r1051 receiver.
Maybe its not on for the weekend. Its a 2 KW signal so should be able to
hear something.
Regards
Paul
WB8TSL

On Fri, Jul 14, 2017 at 9:29 PM, paul swed  wrote:

> Sorry its a bit lower in the site that they resumed broadcasting.
> I thought it had been off for many years. Amazing that they kept the
> transmitter in shape for operation.
> Regards
> Paul
> WB8TSL
>
> On Fri, Jul 14, 2017 at 9:27 PM, paul swed  wrote:
>
>> I went to the wwv site and do not see 25 MHz mentioned. I do see 20 MHz.
>>
>> On Fri, Jul 14, 2017 at 1:17 PM, paul swed  wrote:
>>
>>> Gregory,
>>> I have to be honest and say I didn't even think wwv was on 25 MHz
>>> anymore.
>>> Son of a gun. I will have to listen.
>>> Paul
>>> WB8TSL
>>>
>>> On Fri, Jul 14, 2017 at 1:14 PM, Gregory Beat  wrote:
>>>
 As reported by ARRL, a few days ago, on July 7th the 25 MHz antenna for
 WWV was changed to circular polarization.
 http://www.arrl.org/news/wwv-25-mhz-signal-swapped-to-circul
 ar-polarization

 Matt Deutch, N0RGT the Lead electrical engineer at WWV said it’s hoped
 that the latest antenna change to circular polarization might be helpful to
 anyone studying radio propagation (ionosphere) during next month’s total
 solar eclipse (August 21, 2017), which will be visible across the US.
 “My effort right now is focused on getting the word out, just to make
 people are aware that [the 25-MHz signal] is available, if it can be useful
 to them.”

 greg, w9gb
 Sent from iPad Air
 ___
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 ailman/listinfo/time-nuts
 and follow the instructions there.

>>>
>>>
>>
>
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Re: [time-nuts] DAC performance [WAS: Papers on timing for lunar laser ranging]

[Bob kb8tq]

Hi

> On Jul 16, 2017, at 6:33 PM, Richard (Rick) Karlquist  
> wrote:
> 
> 
> 
> On 7/16/2017 1:51 PM, Bob kb8tq wrote:
>> Hi
>> One gotcha with any ADC or DAC is going to be the reference. There, you are 
>> in the same
>> “get what you pay for” dilemma. Stable and noisy, can do. Quiet and not very 
>> stable, can do.
>> Both stable and quiet, not so easy if you want it cheap.
>> Noise can also be the sigma delta ADC’s weak point. Even at slow rates, some 
>> of them need
>> a lot of averages to quiet down.
> 
> The reference initially used in the E1938A turned out to be too 
> noisy/unstable.  It was non trivial to find an upgrade.  The
> HP Smart Clocks of 20 years ago were limited in their performance
> by the reference used.
> 
> Has there been much improvement in references in the intervening
> 20 years?

They still don’t seem to have the hysteresis problem licked. Yes, you can do an 
oversized reference
and take care of the issue. More or less that’s what you would have done 20 
years ago.

Bob


> 
> Rick N6RK

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Re: [time-nuts] DAC performance [WAS: Papers on timing for lunar laser ranging]

[Richard (Rick) Karlquist]

On 7/16/2017 1:51 PM, Bob kb8tq wrote:

Hi

One gotcha with any ADC or DAC is going to be the reference. There, you are in 
the same
“get what you pay for” dilemma. Stable and noisy, can do. Quiet and not very 
stable, can do.
Both stable and quiet, not so easy if you want it cheap.

Noise can also be the sigma delta ADC’s weak point. Even at slow rates, some of 
them need
a lot of averages to quiet down.



The reference initially used in the E1938A turned out to be too 
noisy/unstable.  It was non trivial to find an upgrade.  The

HP Smart Clocks of 20 years ago were limited in their performance
by the reference used.

Has there been much improvement in references in the intervening
20 years?

Rick N6RK
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Re: [time-nuts] DAC performance [WAS: Papers on timing for lunar laser ranging]

[Bob kb8tq]

Hi

One gotcha with any ADC or DAC is going to be the reference. There, you are in 
the same 
“get what you pay for” dilemma. Stable and noisy, can do. Quiet and not very 
stable, can do. 
Both stable and quiet, not so easy if you want it cheap. 

Noise can also be the sigma delta ADC’s weak point. Even at slow rates, some of 
them need
a lot of averages to quiet down. 

Does this or that design need this or that level of stability or noise? That 
depends a lot on the 
approach used. In a GPSDO, cutting down on the EFC range is a great way to 
“cost reduce” the 
rest of the circuit in terms of noise and stability.  Well made modern OCXO’s 
don’t drift a lot ….

Bob

> On Jul 16, 2017, at 2:24 PM, Charles Steinmetz  wrote:
> 
> Bert wrote:
> 
>> We limited to affordable  and solderable.
>> The LTC1655 was the clear winner because
>> of linearity and temperature
>>  * * *
>> Five years later I know no better alternative
> 
> Well, to name just the first one that comes to mind, how about the LTC1650?  
> Like the 1655, it is available in SO and DIP packages.  Its differential 
> nonlinearity is >2x better than the 1655, it settles 5x faster (4uS vs. 20uS 
> to 1 LSB) and is nearly 100x (40dB) quieter (30nV/sqrtHz vs. 280).  The 1650 
> has substantially lower glitch energy, as well (1.8nV-S for the 1650, 12nV-S 
> for the 1655).
> 
> Not all of the better specs are required for steering an oscillator at GPSDO 
> rates, but others are a distinct advantage.
> 
> I have not surveyed the field to see what other "SO or easier to solder" DACs 
> are available with better performance than the 1655, but I'm sure there are 
> others.
> 
> This is to take nothing away from the 1655 -- I have accounted for thousands 
> of them in my own designs, and think very highly of it.
> 
> Best regards,
> 
> Charles
> 
> 
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Re: [time-nuts] DAC performance [WAS: Papers on timing for lunar laser ranging]

[Charles Steinmetz]

Bert wrote:


 We limited to affordable  and solderable.
 The LTC1655 was the clear winner because
 of linearity and temperature
  * * *
 Five years later I know no better alternative


Well, to name just the first one that comes to mind, how about the 
LTC1650?  Like the 1655, it is available in SO and DIP packages.  Its 
differential nonlinearity is >2x better than the 1655, it settles 5x 
faster (4uS vs. 20uS to 1 LSB) and is nearly 100x (40dB) quieter 
(30nV/sqrtHz vs. 280).  The 1650 has substantially lower glitch energy, 
as well (1.8nV-S for the 1650, 12nV-S for the 1655).


Not all of the better specs are required for steering an oscillator at 
GPSDO rates, but others are a distinct advantage.


I have not surveyed the field to see what other "SO or easier to solder" 
DACs are available with better performance than the 1655, but I'm sure 
there are others.


This is to take nothing away from the 1655 -- I have accounted for 
thousands of them in my own designs, and think very highly of it.


Best regards,

Charles


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Re: [time-nuts] Papers on timing for lunar laser ranging

[Bert Kehren via time-nuts]

As part of our GPSDO work Richard Mc Corkle and I tested multiple DAC's  
using hardware I developed and Richard wrote the code. We limited to 
affordable  and solderable. The LTC1655 was the clear winner because of 
linearity and 
 temperature, see attached. We tested dithering 20 bits and stacking two 
for  coarse fine, storing the test data from using the LTC2400 ADC. Limited 
our  choices to dither and bare use. We did this 5 years ago. Contact with 
Richard  has sadly stopped. I am very concerned, however we continue to use his 
 contributions on several projects with very good results. We use the LTC 
1655 on  Rb's because its resolution and range as is, is perfect. 
Five years later I know no better alternative
Bert Kehren
 
 
 
In a message dated 7/16/2017 5:09:08 A.M. Eastern Daylight Time,  
att...@kinali.ch writes:

On Sat,  8 Jul 2017 11:42:44 -0700
Tim Lister   wrote:

> Forgive the ignorance, but why is there a large disparity  between ADC
> and DAC capabilities ?
> For example, Linear  Technology sell a 24 bit ADC for ~$7 but an 18 bit
> DAC is  $30-50...

Much simplified, it boils down to it being easier to measure  voltage
differences by averaging than keeping a voltage  constant.

E.g. in those >20bit ADC's you will usually find a  delta-sigma ADC,
usually 3rd to 5th order with a 1.5 to 5 bit ADC/DAC  inside. The ADC
and DAC can be laser trimmed to be in the order of 0.1% of  their
ideal values. With a few additional tricks you can get the most  of
the remaining non-linearity out. These tricks also help to  remove
errors due to DC-offsets in the signal path. But the  biggest
improvement comes from averaging over many "samples" to get  the
white noise out. If you look at the usual sample rates at  which
those ADC reach their "full" performance, it is around 
1-30  (output) samples per second.

On the other hand, on a DAC you need to  keep the output voltage
stable. You can do the same delta-sigma approach as  with the ADC
with much the same result, but you have one big problem:
it  is not easy to build an analog low pass filter that has a corner
frequency  down at 10Hz. This means, you have to work at a much higher
frequency to  have a low pass filter that can be realized (let's say 1kHz
if you are  building a discrete filter, higher if it's integrated).
But that means that  you have several orders of magnitude more (white) 
noise.

Additionally,  a lot of people expect to do a couple of 1000 samples
per second at least,  to have a usefull DAC. But that contradicts the
need to have a narrow band  low pass filter to get the noise out.


Attila Kinali
-- 
It is upon moral qualities that a  society is ultimately founded. All 
the prosperity and technological  sophistication in the world is of no 
use without that  foundation.
-- Miss Matheson, The Diamond Age, Neil  Stephenson
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InitialTestResults.pdf
Description: Adobe PDF document
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Re: [time-nuts] Papers on timing for lunar laser ranging

[Attila Kinali]

On Sat, 8 Jul 2017 11:42:44 -0700
Tim Lister  wrote:

> Forgive the ignorance, but why is there a large disparity between ADC
> and DAC capabilities ?
> For example, Linear Technology sell a 24 bit ADC for ~$7 but an 18 bit
> DAC is $30-50...

Much simplified, it boils down to it being easier to measure voltage
differences by averaging than keeping a voltage constant.

E.g. in those >20bit ADC's you will usually find a delta-sigma ADC,
usually 3rd to 5th order with a 1.5 to 5 bit ADC/DAC inside. The ADC
and DAC can be laser trimmed to be in the order of 0.1% of their
ideal values. With a few additional tricks you can get the most of
the remaining non-linearity out. These tricks also help to remove
errors due to DC-offsets in the signal path. But the biggest
improvement comes from averaging over many "samples" to get the
white noise out. If you look at the usual sample rates at which
those ADC reach their "full" performance, it is around 
1-30 (output) samples per second.

On the other hand, on a DAC you need to keep the output voltage
stable. You can do the same delta-sigma approach as with the ADC
with much the same result, but you have one big problem:
it is not easy to build an analog low pass filter that has a corner
frequency down at 10Hz. This means, you have to work at a much higher
frequency to have a low pass filter that can be realized (let's say 1kHz
if you are building a discrete filter, higher if it's integrated).
But that means that you have several orders of magnitude more (white) noise.

Additionally, a lot of people expect to do a couple of 1000 samples
per second at least, to have a usefull DAC. But that contradicts the
need to have a narrow band low pass filter to get the noise out.


Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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