Re: [time-nuts] TV Signals as a frequency reference

[Gerhard Hoffmann]

Am 31.03.2018 um 00:13 schrieb Hal Murray:

fgr...@otiengineering.com said:

   Now that analog TV has gone away, so
   have these signals.

What do the local TV stations use for a frequency reference?

Are there low cost receivers that also produce a good reference frequency?


The German channel ZDF was known to have their line frequency
derived from a Rubidium, when received from the air.
But already on cable, there might have been elastic buffers.

Now with sat and terrestrial TV gone digital, there is no such
thing as a line frequency in the MPEG data stream.
You are 30 years too late  ;-)

But you can find the pseudo noise of the satellite's own
navigation loops abt. 20 dB below the MPEG.
If you know the polynomial, you are back in time nuts land.

The 20 dB are enough that there is no interference. I wonder
how many secret services are parasites on the commercial
TV transponders. The power required for 1 Kbit/sec of
stealth transfer should be much, much lower. Even less when
you just want to disseminate a new key, with the mass transfers
done somewhere else.  Nobody would notice that. Just use
your own polynomial. With a dish on  every house that already
points to the right direction, you just need a modded feed unit.
If that is not tempting!


regards, Gerhard


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Re: [time-nuts] TV Signals as a frequency reference

[paul swed]

Hello to the group.
Been staying clear of the thread as many good comments.
Several things happened that made the color burst signal useless for most
people.
Yes the networks had Cesium's about 3 of them at CBS and the network feed
carried that quality.
but about 1980 a device called a frame synchronizer became popular. $25,000
each. This essentially locked the video to the local house reference.
Generally a free running ovenized crystal. At that point what was sent over
the air had no relationship to the network reference. The benefit of this
device is it allowed glitch-less switching between network and local feeds.
(Staying clear of a gen-lock discussion and terrestrial network microwave
links.)
It was the CBS network color burst that I tinkered with in 1990 to
ultimately see the satellite doppler shift on the CBS signal and other
effects.
Bad news it sort started me on the time-nuttery path and drugs like HP 5360
counters interfaced to computers.
Today the modern mpeg/atsc has none of these qualities and really doesn't
need it. Frame buffers exist in every TV. (Amazing) Originally I thought
ATSC might have value.
Regards
Paul
WB8TSL

On Fri, Mar 30, 2018 at 8:52 PM, Bob kb8tq  wrote:

> Hi
>
>
> > On Mar 30, 2018, at 6:13 PM, Hal Murray  wrote:
> >
> >
> > fgr...@otiengineering.com said:
> >>  Now that analog TV has gone away, so
> >>  have these signals.
> >
> > What do the local TV stations use for a frequency reference?
>
> Anything from a crystal oscillator to a Cs standard. It’s very much a
> “that depends”
> sort of thing. If Crazy Bob is the chief engineer it might be a hydrogen
> maser ….
>
> >
> > Are there low cost receivers that also produce a good reference
> frequency?
>
> As noted earlier, color burst references were a big deal a long time ago.
> Depending
> on how they do what they do it might still be a good bet. The big risk is
> that it could
> be a good bet “most of the time”.
>
> Bob
>
>
> >
> >
> > --
> > These are my opinions.  I hate spam.
> >
> >
> >
> > ___
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Re: [time-nuts] TV Signals as a frequency reference

[jimlux]

On 3/30/18 5:52 PM, Bob kb8tq wrote:

Hi



On Mar 30, 2018, at 6:13 PM, Hal Murray  wrote:


fgr...@otiengineering.com said:

  Now that analog TV has gone away, so
  have these signals.


What do the local TV stations use for a frequency reference?


Anything from a crystal oscillator to a Cs standard. It’s very much a “that 
depends”
sort of thing. If Crazy Bob is the chief engineer it might be a hydrogen maser 
….


And Crazy Bob can convince the owner of the station that it's needed




Are there low cost receivers that also produce a good reference frequency?


As noted earlier, color burst references were a big deal a long time ago. 
Depending
on how they do what they do it might still be a good bet. The big risk is that 
it could
be a good bet “most of the time”.





I wonder how stable the underlying timing of ATSC or DVB-T is?  You 
could recover the carrier or bit clock from an over the air signal, 
should you be lucky enough to live where the signal exists.   It's non 
trivial - all modern receivers do it as part of a single cheap 
monolithic chip - but maybe you could find some SDR code to run on a 
PLUTO or other cheap SDR that lets you "see" that level of the signal.


There's no inherent reason why it should be controlled well, at least 
for ATSC - the receivers are designed to tolerate multipath, Doppler, 
and other impairments.


But for simulcasting, the various transmitter carriers need to be 
matched fairly well.

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Re: [time-nuts] TV Signals as a frequency reference

[Tisha Hayes]

It might of been fairly easy to use an old NTSC television signal as a
frequency reference (lumina, chroma or audio carriers). Now that it is
converted over to ATSC it would be much more difficult to recover a
reference frequency using readily available electronics.

You would have a much better chance of locking on to a commercial FM
carrier (88-108 MHz). Some are quite accurate with less than 0.5 Hz of
error.

If you want both time and frequency then a GPS source is your best bet. You
can get something like a ebay surplus Trimble Thunderbolt for less than
$150.

Tisha Hayes, AA4HA

*Ms. Tisha Hayes*


On Fri, Mar 30, 2018 at 5:13 PM, Hal Murray  wrote:

>
> fgr...@otiengineering.com said:
> >   Now that analog TV has gone away, so
> >   have these signals.
>
> What do the local TV stations use for a frequency reference?
>
> Are there low cost receivers that also produce a good reference frequency?
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
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Re: [time-nuts] TV Signals as a frequency reference

[Bob kb8tq]

Hi


> On Mar 30, 2018, at 6:13 PM, Hal Murray  wrote:
> 
> 
> fgr...@otiengineering.com said:
>>  Now that analog TV has gone away, so
>>  have these signals. 
> 
> What do the local TV stations use for a frequency reference?

Anything from a crystal oscillator to a Cs standard. It’s very much a “that 
depends”
sort of thing. If Crazy Bob is the chief engineer it might be a hydrogen maser 
….

> 
> Are there low cost receivers that also produce a good reference frequency?

As noted earlier, color burst references were a big deal a long time ago. 
Depending
on how they do what they do it might still be a good bet. The big risk is that 
it could
be a good bet “most of the time”.

Bob


> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] TV Signals as a frequency reference

[Hal Murray]

fgr...@otiengineering.com said:
>   Now that analog TV has gone away, so
>   have these signals. 

What do the local TV stations use for a frequency reference?

Are there low cost receivers that also produce a good reference frequency?


-- 
These are my opinions.  I hate spam.



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[time-nuts] TV Signals as a frequency reference

[Francis Grosz]

Hal Murray (hmur...@megapathdsl.net) said:

"Roughly 40 years ago, a friend showed me a NBS booklet describing a scheme
for distributing time via TV.  I forget the details.  It was a cooperative
project with one of the major networks.  NBS published the propagation delays
which changed occasionally as the phone companies providing the underlying
links rerouted things.

This is an IEEE article from 1972 that looks like a good fit:
  Nationwide Precise Time and Frequency
  Distribution Utilizing an Active Code Within
   Network Television Broadcasts
DAVID A. HOWE
https://www.researchgate.net/publication/3092613;

 I was a TV Broadcast Engineer in the 70s.  There were a number of
schemes for transmitting frequency standard information via the TV
signal.  One used the VITS signal referenced above.  Another used a
cesium standard to control the 3.58 MHz (actually 3.579545454... MHz)
color burst signal.  There were several articles in the hobbyist
press at the time on using this for a standard.  You had to be
careful to use a network program, however; most local station could
not afford a cesium reference for something like that.  (Actually,
the station I worked for had one but it was used for controlling the
transmitter frequency.  Long story).  Now that analog TV has gone
away, so have these signals.

 Francis Grosz

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Re: [time-nuts] Ultralink

[John Ackermann N8UR]

Hi Brooke --

Yes, all the chips on the board are low power devices.  I'm measuring 
the receiver as drawing 0.9 MA at about 2.3 volts.


Update -- I moved the receiver and farted around with the wiring, and 
now the S-Meter is off the peg, responds to orientation changes, and I 
actually got a couple of indications of bits being decoded.  So, I think 
the hardware is working fine.


However, there must be a lot of local interference as decoding is very 
erratic and I'm nowhere near getting a full sequence.  I don't have any 
experience at this location with WWVB reception, so I'm not sure what to 
expect.  At my previous Ohio house a mile south of here the signals were 
very good and there were no noticeable problems with the Spectracom 
receivers (may they rest in peace).  Next step is to experiment with 
receiver placement.


John

On 03/30/2018 03:15 PM, Brooke Clarke wrote:

Hi John:

The U4226B chip operates at very high impedance levels in order to 
minimize battery drain in its main application, battery powered clocks.

So some sort of buffer is needed on all the output pins.

The 333 model, with the analog meter, was made for the folks working for 
WWVB as a way for them to know the transmitter was on the air.

http://www.prc68.com/I/timefreq.shtml#WWVBrcvr
http://www.prc68.com/I/Loop.shtml (WWVB)


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Re: [time-nuts] Ultralink

[Brooke Clarke]

Hi John:

The U4226B chip operates at very high impedance levels in order to minimize battery drain in its main application, 
battery powered clocks.

So some sort of buffer is needed on all the output pins.

The 333 model, with the analog meter, was made for the folks working for WWVB as a way for them to know the transmitter 
was on the air.

http://www.prc68.com/I/timefreq.shtml#WWVBrcvr
http://www.prc68.com/I/Loop.shtml (WWVB)

--
Have Fun,

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

 Original Message 

On 03/30/2018 03:39 AM, Hal Murray wrote:


t...@leapsecond.com said:

I updated http://leapsecond.com/museum/ulio/ with more manuals, and many
exterior / interior photos of the 301 module.


Thanks. My 301 says it is a 30TH Rev-A - mostly through hole parts.  Same
layout.


Mine is the same.  Circuit is very simple.  The 20 pin IC is the U4226B receiver chip and it has two external 60 kHz 
filter resonators.  The 8 pin DIP is a TLV2770C op amp which seems to be a buffer to drive the S meter from the very 
high impedance AGC test point on the receiver chip. And I am guessing that the 2N3904 transistor is a buffer for the 
time code output.


The modular cable connecting the receiver to the decoder is wired straight through, not reversed as most telephone 
cables are.  My fear is that someone (like me) might at one point have used a reverse cable and thus put reverse 
polarity on the board; I don't see any reverse power protection.


Later today I'll tap into the four conductors on the cable and see what signals I see on them, and also look for signs 
of life on the receiver chip.


BTW -- Donald Resor pointed me to UTSource which shows several Chinese vendors as having them in stock.  I get nervous 
about whether they are the real thing or not, but will probably order a couple just in case. The chip is a 20 pin 
TSSOP package, which isn't too hard to rework but before putting hot air on the receiver board there are one or two 
surrounding parts one would want to remove to avoid collateral damage.


John
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Re: [time-nuts] WWV/CHU

[Bob kb8tq]

Hi


> On Mar 30, 2018, at 12:42 AM, Hal Murray  wrote:
> 
> 
> jim...@earthlink.net said:
>> Hal, you should know better than to have a question like "get time" on this
>> list without specify the precision and accuracy . 
> 
> I was thinking of measuring the results, and maybe comparing various 
> receivers if I get that far.
> 
> "Good enough" for me would be to see the change in prop delay from night to 
> day.
> 
> 
>> I was in a meeting yesterday with a lot of technical people, discussing
>> testing an HF receiver, and I mentioned WWV as a source, and there were  a
>> combination of blank looks and amused/amazed looks (at the blank  looks) -
>> OK, so now we know who in the room are the computer only people  (WWV? is
>> that some sort of NTP protocol?) and who  are the radio people 
> 
> I listened to WWV as a kid.  I think my father told me about it.  (We had a 
> good collection of old tube radios.)
> 
> Roughly 40 years ago, a friend showed me a NBS booklet describing a scheme 
> for distributing time via TV.  I forget the details.  It was a cooperative 
> project with one of the major networks.

Back in the era when the network stations all “went direct” to the mothership 
for their
signal, all the sync pulses ultimately could be traced back to network HQ. That 
changed
when local frame buffers (and other forms of translation) became the “way to do 
it”. The
TV based sync timing survived in the Washington DC area longer than the rest of 
the
country. It may even still be active …..

Bob


>  NBS published the propagation delays 
> which changed occasionally as the phone companies providing the underlying 
> links rerouted things.
> 
> This is an IEEE article from 1972 that looks like a good fit:
>  Nationwide Precise Time and Frequency
>  Distribution Utilizing an Active Code Within
>   Network Television Broadcasts
>DAVID A. HOWE
> https://www.researchgate.net/publication/3092613
> 
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] . Re: WWV/CHU (jimlux)

[Andre]

Hi, I modified my RTL-SDR by adding a blue LED on one side of the crystal.
This helped a bit but there is still a little variation with temperature.

Anyone else run into this problem?
It seems spot-on when checked against available standards but lack an atomic 
reference.

-Andre
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Re: [time-nuts] Ultralink

[John Ackermann N8UR]

On 03/30/2018 03:39 AM, Hal Murray wrote:


t...@leapsecond.com said:

I updated http://leapsecond.com/museum/ulio/ with more manuals, and many
exterior / interior photos of the 301 module.


Thanks. My 301 says it is a 30TH Rev-A - mostly through hole parts.  Same
layout.


Mine is the same.  Circuit is very simple.  The 20 pin IC is the U4226B 
receiver chip and it has two external 60 kHz filter resonators.  The 8 
pin DIP is a TLV2770C op amp which seems to be a buffer to drive the S 
meter from the very high impedance AGC test point on the receiver chip. 
And I am guessing that the 2N3904 transistor is a buffer for the time 
code output.


The modular cable connecting the receiver to the decoder is wired 
straight through, not reversed as most telephone cables are.  My fear is 
that someone (like me) might at one point have used a reverse cable and 
thus put reverse polarity on the board; I don't see any reverse power 
protection.


Later today I'll tap into the four conductors on the cable and see what 
signals I see on them, and also look for signs of life on the receiver chip.


BTW -- Donald Resor pointed me to UTSource which shows several Chinese 
vendors as having them in stock.  I get nervous about whether they are 
the real thing or not, but will probably order a couple just in case. 
The chip is a 20 pin TSSOP package, which isn't too hard to rework but 
before putting hot air on the receiver board there are one or two 
surrounding parts one would want to remove to avoid collateral damage.


John
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Re: [time-nuts] WWV/CHU

[Hal Murray]

t...@leapsecond.com said:
> In general, if the author or paper is related to NIST, the original
> copyright-free PDF will be available in the NIST Time and Frequency
> Publication Database. That easily searchable database, and the thousands of
> papers it contains, is probably the greatest asset we time nuts have. For
> those of you that don't know it yet, check it out:

> https://tf.nist.gov/general/publications.htm 

Thanks.

Another other great resource (non time-nut) is NIH Pubmed.

I think the deal is that they get to distribute a copy of any paper from 
research that they finance.  I think the publisher gets 6 months or a year 
before the NIH free version goes online.

I assume the publishers freaked out when the idea was first announced.  
Anybody know of a paper discussing that issue?



-- 
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Re: [time-nuts] Ultralink

[Hal Murray]

t...@leapsecond.com said:
> I updated http://leapsecond.com/museum/ulio/ with more manuals, and many
> exterior / interior photos of the 301 module. 

Thanks. My 301 says it is a 30TH Rev-A - mostly through hole parts.  Same 
layout.


-- 
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Re: [time-nuts] Ultralink

[Tom Van Baak]

> I have a 333 box with 301 antenna.  It was a gift several years ago.  The 
> display updates, but the meter never gets off 0.  At the time, I thought the 
> new modulation scheme had killed it and didn't investigate.  But tvb 
> suggested it should still work, so I took the cover off.

Hal,

I tested several old Ultralink WWVB receivers this evening and, yes, they work 
fine. The products were designed for precise timing rather than stabilized 
frequency. Thus they don't rely on the carrier and are not caught by the 
"enhanced" WWVB format that killed all the Spectracom WWVB receivers.

Model 332 has small LCD with date, time, status display.
Model 333 has larger LCD and calibrated analog signal level meter.
Both connect to a remote model 301 antenna module.
Yes, the antenna module contains a Temic U4226B.

My 333/301 signal levels idle at around +9 or +10, and bounce down each second 
as expected.

I updated http://leapsecond.com/museum/ulio/ with more manuals, and many 
exterior / interior photos of the 301 module.

Hopefully you and John can get yours working. Let me know on- or off-list if 
there's anything I can do to help.

/tvb

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