Yes indeed. I also have a hp rcvr. But Pauls request was for an alternate
approach.
I regularly matched LORAN C wwvb and GPS. It was nice having an alternate.
wwvb really isn't but its about all we have now.

On Mon, Oct 4, 2010 at 8:53 PM, K3WRY@aol.com wrote:

Doesn't someone on here with a Ham license have a Cs standard and "could"
put up a 1pps signal?  Simply transmit your callsign within the 1pps (there
has to be a way) and we have a non-Govt. time standard "if needed".  A
simple 1pps PSK-31 (or other digital mode) signal would probably work and be
completely legal.  Let's do this on our own and not rely on Govt. or GPS...
Several throughout the world acting together (I'm not a programmer so
someone could step up and figure out the logistics for a receiver) and we
would have an alternative to GPS (IF/when it stops working).

Yes?  Just a thought...

73 Brice KA8MAV

----- Original Message -----
From: "paul swed" paulswedb@gmail.com
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Monday, October 04, 2010 10:53 PM
Subject: Re: [time-nuts] 60 KHz Receiver

Yes indeed. I also have a hp rcvr. But Pauls request was for an alternate
approach.
I regularly matched LORAN C wwvb and GPS. It was nice having an alternate.
wwvb really isn't but its about all we have now.

On Mon, Oct 4, 2010 at 8:53 PM, K3WRY@aol.com wrote:

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
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and follow the instructions there.

Heathkid wrote:

a) broadcasts aren't legal for US hams
b) ionospheric uncertainty in the skywave path makes this no better than WWV
c) Whats wrong with GPS and/or WWV and/or CHU or whatever?
d) A cheap Rb would give you a local reference that is much better than
what you could do with receiving something via skywave.

If you want something that isn't run by governments,and is a technical
challenge, how about pulsars?  I'd guess (not having looked into it at
all) that is would be cheaper to set up a station to receive pulsars
than to run a Cs standard.

While I fully sympathize with the "stand alone" approach (that's one of
the appeals of HF comms in general.. you aren't depending on anyone
else's infrastructure), I don't know that setting up a time standards
station fits in with that..

Uhmmm.... There is this station called WWV that does just that on
at least 5, 10 and 15MHz.

And if you are worried about it being broadcast by the US government,
you can always try CHU in Canada.

And if you are worried about the station being in North America,
there are time stations in virtually every corner of the world.

-Chuck Harris

Heathkid wrote:

Pulsars take a big dish and they aren't all that good as a standard. A
friend of mine proved that at Aricebo years and years ago.

I've vaguely heard that there are some new ham allocations in the works
below 500 KHz. How about setting up a beacon network that works like
LORAN, but at a different frequency. A simple downconverter could then
feed the signal into a LORAN receiver?

FWIW,

-John

==============

Wow.... you really missed my point and by having someone
listening/monitoring it is not broadcasting.  Especially if it is in reality
for the most part... telemetry.

Maybe I wasn't clear or maybe my message could have been misunderstood.  For
that, I am truly sorry.  I was thinking along the lines of what John stated,
"a beacon network that works like LORAN...".

• I'll shut up now and go back to just reading the posts for another month
  or so..."

73 Brice KA8MAV

----- Original Message -----
From: "jimlux" jimlux@earthlink.net
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Monday, October 04, 2010 11:39 PM
Subject: Re: [time-nuts] 60 KHz Receiver

Another thought: Does anybody know if the LORAN frequency band has been
re-assigned. If not, I wonder if it could be gotten as a ham band?

FWIW,

-John

===============

One more note before I just "read the posts for a while"...

Do some reading on telemetry and when broadcasts ARE allowed.  I've been a
Ham for more than 30+ years.

No kidding... but without GPS (and assuming no Internet as well) how do we
sync our clocks besides RF?

Nothing as long as they are TRANSMITTING.

I have three Rb standards to go along  with my two Thunderbolts.

Are you serious?  Cheaper?  Really?  I'll trade you a Thunderbolt...
complete kit! for a full Pulsar time/frequency reference receiving station
that is reliable (and the real-estate plus equipment for a dish large enough
for it!).  ;)

I have many mechanical watches.  I can easily calculate NOON from the sun
at anytime during the year.  That's a reference and I can "set my watch by
it".  I don't need you or anyone else to tell me what time it is.  If my
watch isn't accurate or precise or is off my 1mS/day (or hour)... does it
really matter if the GPS sats are down (think about it... why would they
be down)?

What time is it?

that wasn't my point  ---- it's "relative" and I'm not going to go further
with this discussion.  I just thought a "time-nuts based time system" was an
interesting prospect.

...done.

Hi

The bandwidth of anything close to a Loran signal is a lot wider than any of the ham bands contemplated below 1 MHz.

There's the minor issue of getting the power company to put in a cable to the house for your 1 Mw (capital M not lower case M) transmitter.

Even though it's pule, the RF power is way beyond the sub 1 W outputs currently contemplated on those bands. Signal to noise does matter.

Bob

On Oct 5, 2010, at 12:20 AM, J. Forster wrote:

In message B69FDCAF-2B39-4575-B5CD-66A87FA1B332@rtty.us, Bob Camp writes:

You know, there are other ways to skin that cat these days.

Old-time signals had to be grossly inefficient because the receivers
were inefficient, in particular the "ear-wristwatch" kind of time
receivers.

These days we have spread-spectrum modulation, and if our only goal
is to transmit a timestamp, you can spread pretty wide and far and
need very little power to produce a receiveable signal at long
distances.

The QRSS hams are playing around with numbers like 17,840,000 miles
per watt, and all it takes to turn that into a time/frequency
services is a spreading function with a really good autocorrelation.

Obviously, you will not get second by second measurements, but the
measurements you do get, say once per hour, will have much higher
precision because of the averaging that goes into them.

And equally obvious: propagation effects will take their toll, but
still...

Somebody with a license should try that on 137kHz...

Poul-Henning

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

Hi

If you were starting from scratch there are a lot of things you could do. If the intent is to put out something a Loran receiver will recognize ... not so much.

Bob

On Oct 5, 2010, at 6:44 AM, Poul-Henning Kamp wrote:

A great thread by everyone. Oh to make the loran receivers work. But that is
indeed the past. Can not hear Europe on east coast.
But the question really is, what do you want to accomplish? I don't think
its a time stamp. Its just to easy to get it from GPS or the network. But
that could be a secondary use. I believe the primary goal would be frequency
distribution with perhaps a tick.
If this is the goal then I am 100% in agreement that there are far more
efficient modulation and recovery methods today. The trick is you need
something that does not effect the accuracy of the timing and may improve
the various transmission issues at these frequencies. By the way this list
has a heck of a brain trust so its very very possible.
Someone mentioned spread spectrum. Thats very interesting as it is what GPS
uses and could work at these lower frequencies.
Like the  "Hey this is just telemetry" comment. You know the FCC does indeed
give temp authorization for quite long periods of time. Years in fact.
So I would be in the keep it simple mode.
Great a single carrier with a id every 10 min. Maybe that could be waved to
1 per hour or 24 hours. Unfortunately then we have nothing better then wwvb.
The modulation method may be key and then what freq we would use. BPSK at
higher frequencies is also impressive.
My first contact was in the indian ocean on 5 whats from boston.
Regards
Paul
WB8TSL

On Tue, Oct 5, 2010 at 6:59 AM, Bob Camp lists@rtty.us wrote:

One other comment
Would be great to be on 100KC
But I might guess some one in gov will wake up to suggest that it could
interfere with europe and not allow it. Or the treaties exist to forbid
reuse.

On Tue, Oct 5, 2010 at 8:57 AM, paul swed paulswedb@gmail.com wrote:

Were it me, I would change the model from a few high power
transmitters netted together to a ton of WiFi routers running
special software and netted together.

-Chuck Harris

paul swed wrote:

I was not contemplating a global navigation system. Just enough to get a
LORAN type timing, not navigation, lock over a few hundred mile radius.

-John

=============

Millisecond pulsars have been proposed as being suitable as comparable to atomic clocks.

I don't know how much power they put out, but there are stories about people with backyard size dishes receiving pulsars.  Not sure if they're the right kind of pulsar, though.  But hey, when fabricating your own Cs fountain or H maser seems boring.....

On Oct 4, 2010, at 9:20 PM, "J. Forster" jfor@quik.com wrote:

Paul,

I'd bet there are 50+ LORAN timing receivers in the Boston area that could
receive and lock to an erzatz 5W signal from a simulator and small amp.

-John

=============

On Oct 4, 2010, at 9:43 PM, "Heathkid" heathkid@heathkid.com wrote:

The FCC is kind of down on transmissions not intended for a specific recipient.  There are some exceptions, and informal agreements (e.g. Aprs isnt to a specific recipient, but is intended for one of a group) Not a big deal though, you  can get an. Experimental license, though...

You could do an experiment like that with a group, but I don't think it's viable as a continuing operation.

And besides, I don't know that it really "fills a need"...  HF isn't great for time distribution, and there aren't suitable bands for hams down low.

Naah....  All ideas are interesting, and just because I don't think it's great doesn't mean that someone else might not think it's the bees knees....

In message AANLkTi=-ReJGQKAObGshqz=jFHCB5Bd6zezy596UA2Gn@mail.gmail.com, paul
swed writes:

There is no reason the ID could not be worked into your spreading function
so the time to send it would not be lost.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

In message AANLkTinnOcH7bSqsovhPN3QdohAPG2Pi2w5YNRYjF90X@mail.gmail.com, paul
swed writes:

Here in Denmark 100KHz is dual-licensed and open for low power
unlicensed use, because nobody in their right mind would expect a
few watts to ever be able to drown out Loran-C...

Poul-Henning

Exact text from Danish frequencyplan, will not attempt translation
to avoid corrupting meaning:

Mobile tjenester er begrænset til laveffekts radioanlæg.

Laveffekts radioanlæg:

Radiogrænseflade nr. 00 008 for laveffekts radioanlæg med
spoleformede antenner.

Radiogrænseflade nr. 00 023 for aktive medicinske implantater
med ultra lav sendeeffekt.

Anvendelse af radiofrekvenser i radioanlæg som nævnt i
radiogrænseflade nr. 00 008 og nr. 00 023 må ske uden
individuel tilladelse til frekvensanvendelse, jf. bekendtgørelse
nr. 1119 af 27. november 2009 om anvendelse af radiofrekvenser
uden tilladelse samt om amatørradioprøver og kaldesignaler
m.v.

100 kHz: ATC.

Militær anvendelse.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

On Oct 4, 2010, at 10:26 PM, "Heathkid" heathkid@heathkid.com wrote:

Telemetry is allowed only in the sense that it is to a specific recipient(s). That's sort of different from a beacon on hf...  I don't know how the ncdxf beacons are licensed.. They may have a STA

But legality is the least of the issues..  If you set it up and you're not annoying anyone, I doubt you'll get hassled much..

The way it's been done for centuries... Astronomical or traveling clocks or wireline.
How close do you want to sync.. HF paths are probably only good to milliseconds.

Sure.. As an academic exercise I can see wanting to figure it out, and even doing it as an experiment for the thrill.  But If wwv isn't on the air, I don't see hams stepping in to fill the need.  And if it's self reliance,then a local atomic reference seems a better approach.

So you want to be able to sync your local ref to some other standard?

That is more of an ad hoc thing than setting up a beacon, etc.

Were not comparing to Tbolts here.. You suggested that someone connect a Cs to some stable transmitter, etc.  I think an amateur pulsar receiving system is comparable to the Cs setup.

Now, if it's that you want someone else to put up the station, so you don't have to spend the time and money<grin>,  You've got some selling to do...

It is interesting.. And figuring out how to do precision time/frequency in an infrastructure-lite environment is challenging, Especially if you want to do it in an adhoc way fairly quickly.

It might be cloudy/smoky. Gps and wwv might be unavailable because of interference, locally.

So there is value in thinking about it.  What I don't think there is value in is someone trying to set up a wwv light using psk31 on a continuing basis.  And that's just my opinion. There are lots of things other hams do that I think aren't particularly useful or valuable, just as there are things that I do ham-wise that others think are wastes of time.

Jim

Have you ever tried to adjust a local standard to better than 1 in 10E7
using WWV or CHU?

And which one do you believe? If any?

-John

==============

Speaking of LORAN receivers, I have two Stanford Research Systems FS700
receivers here at work (in central VA) that I have been asked to dispose of.
They both have ovenized oscillators, and I have one original manual. The
antenna is on the roof, but I think it'll stay there ;-). Any offers for one
or both?

73,

geo - n4ua

On Tue, Oct 5, 2010 at 8:57 AM, paul swed paulswedb@gmail.com wrote:

In message AANLkTikT7xxjGaNyXgaDa1kqN4MkmQ0xcw=B_2VLniCx@mail.gmail.com, Geor
ge Dubovsky writes:

I would love to lay my hands on one of them, so I can compare the performance
to my home-built stuff.

I'm willing to pay for the shipping across the pond.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

John I would be interested but with loran down fo ever. Inexpensive.

On Tue, Oct 5, 2010 at 1:24 PM, George Dubovsky n4ua.va@gmail.com wrote:

"There's the minor issue of getting the power company to put in a cable to the house for your 1 Mw (capital M not lower case M) transmitter."

I can't resist citing a personal anecdote regarding power distribution.
A few years back, I was working on a proposal for a high power (1MW) power supply system. Our building currently has about 750kW service, so I asked the facility engineer to call the power company to find out how much it would cost and how long it would take to get another MW in our building.
He called me back quickly. He was told that because he called after 2PM, they could not do it that day and the soonest we could have it would be the next day. He was laughing so much, he never got to ask how much it would cost...

Didier

Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: Bob Camp lists@rtty.us
Sender: time-nuts-bounces@febo.com
Date: Tue, 5 Oct 2010 06:34:29
To: Discussion of precise time and frequency measurementtime-nuts@febo.com
Reply-To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: Re: [time-nuts] 60 KHz Receiver

Hi

The bandwidth of anything close to a Loran signal is a lot wider than any of the ham bands contemplated below 1 MHz.

There's the minor issue of getting the power company to put in a cable to the house for your 1 Mw (capital M not lower case M) transmitter.

Even though it's pule, the RF power is way beyond the sub 1 W outputs currently contemplated on those bands. Signal to noise does matter.

Bob

On Oct 5, 2010, at 12:20 AM, J. Forster wrote:

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

That is basically the sauce behind GPS. What is the power of the transmitters on the satellites? It can't be much, and the signal on the ground is quite a bit below the noise floor before correlation.

Didier
Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: "Poul-Henning Kamp" phk@phk.freebsd.dk
Sender: time-nuts-bounces@febo.com
Date: Tue, 05 Oct 2010 10:44:39
To: Discussion of precise time and frequency measurementtime-nuts@febo.com
Reply-To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: Re: [time-nuts] 60 KHz Receiver

In message B69FDCAF-2B39-4575-B5CD-66A87FA1B332@rtty.us, Bob Camp writes:

You know, there are other ways to skin that cat these days.

Old-time signals had to be grossly inefficient because the receivers
were inefficient, in particular the "ear-wristwatch" kind of time
receivers.

These days we have spread-spectrum modulation, and if our only goal
is to transmit a timestamp, you can spread pretty wide and far and
need very little power to produce a receiveable signal at long
distances.

The QRSS hams are playing around with numbers like 17,840,000 miles
per watt, and all it takes to turn that into a time/frequency
services is a spreading function with a really good autocorrelation.

Obviously, you will not get second by second measurements, but the
measurements you do get, say once per hour, will have much higher
precision because of the averaging that goes into them.

And equally obvious: propagation effects will take their toll, but
still...

Somebody with a license should try that on 137kHz...

Poul-Henning

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

It is a pulse transmitter.  It makes short bursts of 10 or 12 pulses,
and then waits one GRI, and then does it again.  I would think the
actual continuous power draw is around 10Kw.

The floor is open to anyone that wants to make the calculation.

-Chuck Harris

shalimr9@gmail.com wrote:

On Oct 5, 2010, at 1:15 PM, shalimr9@gmail.com wrote:

If I recall correctly, the transmit power is around 15W. A received signal of -130dbm is considered strong, and tracking (but not acquisition or data decoding) can still be done at signals approaching -160dbm.

--
Mark J. Blair, NF6X nf6x@nf6x.net
Web page: http://www.nf6x.net/
GnuPG public key available from my web page.

In message 4CAB888B.4040604@erols.com, Chuck Harris writes:

http://phk.freebsd.dk/photos/L9007M/dscf0458.jpg.html

About 50kW for Eiði (400kW, 9007M)

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

That's why I think an amateur timing LORAN network might be quite
feasable. Imagine a dozen 1 KW PEP A-LORAN stations with Rb and GPS
scattered around the US. There is no reason why a single transmitter could
not spoof a whole chain as it would not be used for navigation.

FWIW,

-John

=============

Ok, but that is no megawatt!

Also, most of the transmitters were doing multi duty, handling
several chains simultaneously.  That would up the average power
proportionately.

-Chuck Harris

Poul-Henning Kamp wrote:

And the Power Factor sucks, so there is a lot less real power being used.

-John

=============

In message 50213.12.6.201.2.1286311041.squirrel@popaccts.quikus.com, "J. Fors
ter" writes:

Yeah, 0.75 inductive is not exactly stellar, but it may not matter in
this case, as the Faroese power-grid is pretty sparse.

Poul-Henning

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

Not necessarily, on 3 phase systems, you would have to be creative to get below .9

You can easily get to .95 with a simple multipulse rectification. Beyond that, other than regulatory compliance, you do not gain much efficiency.

I can't imagine these systems running on anything other than 3 phase power.

Didier

Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: "J. Forster" jfor@quik.com
Sender: time-nuts-bounces@febo.com
Date: Tue, 5 Oct 2010 13:37:21
To: Discussion of precise time and frequency measurementtime-nuts@febo.com
Reply-To: jfor@quik.com, Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: Re: [time-nuts] 60 KHz Receiver

And the Power Factor sucks, so there is a lot less real power being used.

-John

=============

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Well crazy as it sounds if you are at 100 KC you might just want 1 loran
tower in a chain or even fewer. You only need 1 station not 3. Timing rcvrs
worked on one signal.

On Tue, Oct 5, 2010 at 4:46 PM, shalimr9@gmail.com wrote:

In message 63077.12.6.201.2.1286310871.squirrel@popaccts.quikus.com, "J. Fors
ter" writes:

Why try to emulate technology from WWII ?

I would find it much more interesting to invent a good spread-spectrum
modulation, and see if we could do world wide time-transmission with
just a single 1W tranmistter per continent, which could be received
with a simple down-converter frontend and a soundcard.

Poul-Henning

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

??

Paul, I've said that at least twice. A single Tx can emulate all the Txs
in a chain, since it is not used for navigation.

Just emulating the Master station would be fine, but I'm not certain that
all LORAN receivers would lock up, absent two or three received stations.

I'd set up my time differences to put the fake "position" on top of the
Prudential or Bunker Hill Monument or some other landmark, if I were in
Boston.

FWIW,

-John

================

Because there is a now-useless installed base of high grade LORAN
receivers and comparators out there.

IMO, one Tx site could make them all live again.

-John

===============

Yup running in circles.
Not in favor of soundblaster.
Looses accuracy
Am in favor of spreadspct

On Tue, Oct 5, 2010 at 5:06 PM, J. Forster jfor@quik.com wrote:

On 10/5/2010 3:59 PM, paul swed wrote:

Frequency recovery works with master only, timing requires ranging data,
so three stations are required to locate the receiver.

--
mailto:oz@ozindfw.net
Oz
POB 93167
Southlake, TX 76092 (Near DFW Airport)

Hi

Ok, the next layer to this onion is the antenna. At 100KC your antenna is 35X smaller than it is on 80 meters foot for foot. In other words, your 100' tall vertical on 80 equates to a <3 foot tall antenna at 100 KC. QRP on 80 with a 3' transmit antenna anybody? Been there done that, not much range at all. At VLF forget about transmitting with a horizontal antenna unless you are airborne.

It's not just the antenna, the ground counts as well. If you are by the seashore that may not be a big deal. If you are inland, prepare to lay many very long radials.

After that you hit signal to noise. The receivers worked as well as they did because they had an enormous signal to work with. There's an amazing amount of crud running around down below 200 KHz these days. Even for timing you need a lot of signal to get good results.

Bob
KB8TQ

Ham for way more than 30 years....

On Oct 5, 2010, at 4:59 PM, paul swed wrote:

A loop around the house?

-John

==============

Hi

I've had similar experiences with commercial power (we can't get the new transformers up on the pole this evening, but we can have it done by noon tomorrow...).

The same call on a residential circuit gets you endless grief about tariffs and their poor aching back. Lucky if you can even double the circuit in under a couple months.

Bob

On Oct 5, 2010, at 4:13 PM, shalimr9@gmail.com wrote:

Hi

Same gotcha as the horizontal dipole - most of the energy is shorted out by the ground. Think of a transformer with a shorted turn.

Bob

On Oct 5, 2010, at 5:58 PM, J. Forster wrote:

Poul,

Please explain to me how spread spectrum would enhance any process of frequency or
time recovery ?

I just do not see it.

The reason for the spread spectrum used with the GPS is because all of the Birds
are in the same base frequency.  Thus the spreading codes allow for distinction
between the different signals.

At 100 kHz the system bandwidth is very, very limited compared to the very wide
spectrum of the GPS.  Stepping up into the HF area brings in the sky wave
propagation issues.

The whole purpose of suggesting an amateur approach is to utilize the large base of
existing LORAN receivers as someone pointed out.  However, as the number of people
needing such a service is quite small it does not make economical sense, as the
cost would certainly be prohibitive.  The only feasible way would be to have many
lower power 100 kHz transmitters and there are just not enough people around to
construct, install and maintain such an operation; not to mention the licensing
issues.

Besides, you would achieve nothing above what is already provided by operations
such as the 60 kHz WWVB and similar in other countries.  So I see it as a pie in
the sky nice idea but no cigar.

Bill....WB6BNQ

Poul-Henning Kamp wrote:

Depends on your soil. New England is mainly rock with very poor conductivity.

-John

==============

The localized LORAN is not that hard, IMO:

Many TNs have GPS & Rbs.
At least one simulator has been built.
RF amps are easily available (ENI) for 100W pulse at 100 KHz.
Home Depot has 250' rolls of #14 THHN.

FWIW,

-John

============

On 10/05/2010 03:17 PM, J. Forster wrote:

However, consider that a few of these transmitters if wisely used could
be kept running by guys like us on electricity bills we could handle and
provide a grid network. This way the navigation aspect could be embedded
into the system and propagation delay be cancelled. Fixed location could
then be used to provide multiple observations of time-indication.

A particular aspect of spread spectrum is that we could have several
transmitters on the same center frequency which has the benefit that
equipment delays become common mode to a first degree. This is a benefit
of GPS over GLONASS.

Multiple carrier systems provide means for frequency diversity as well
as dispersion observations.

There is many options to consider for such a system.

Cheers,
Magnus

On 10/5/2010 5:14 PM, WB6BNQ wrote:

I can see a lot of reasons, but it's an answer requiring lots of
thought.  I'm not certain that it'd be an advantage.  Some things that
come to mind are:

1. non-gaussian interferers would be reduced by the spread processing
   gain. (Yay!)
2. With a long enough code you can discriminate against multipath
   (skywave.) as well as Loran - really limiting diurnal shift.
3. With a high chip rate you can potentially get really fine time
   resolution.
4. Most of the processing goes right to bits - Moore's law becomes
   our buddy.

--
mailto:oz@ozindfw.net
Oz
POB 93167
Southlake, TX 76092 (Near DFW Airport)

In message 4CABA343.8C5812B1@cox.net, WB6BNQ writes:

Ok, it is late and I'm probably going to botch this, but I'll try:

The really short explanation is that your carrier transitions have
random-ish looking signs, which, if properly designed, allows you to
balance out pretty much any kind of CW or random noise.

This is, in essence, why you can separate the different GPS
sattelites, even though they all send on the same frequency.

Technically speaking, Loran-C is spread spectrum, but they botched
this aspect slightly, by not properly balancing the signs of (all)
the codes.

The Austron 2000 has a switch that allows you to disregard certain
bits in the codes to balance them, this increases the imunity to
CW interference.

So given that you can trivially get a good OCXO today, I would design
our "low-power-time-transmitter" to send one fix per hour.

For instance 127 bits of PRNG at 28 seconds per bit with a four
second gap before the next timestamp (send ID ?)

On the receiver side, you know what time it is +/- one 28sec bit,
so you digitize the signal and correlate the PRNG in a window around
your local clock.

After an hour, you pick the correlation bucket that correlated best
and have an instant estimate of the difference between your local
clock and the average of that hours transmissions.

If xmitted as NFSK at around 100kHz and digitized at 1MSPS, you
would get 1µsec resolution without resorting to interpolation.

By choosing all your magic numbers to be nonprime to normal
CW signals inside their respective periods, you supress those
by averaging.

This is why the NELS LORAN-C chains got new 4-digit GRI's: they
are imune to pretty much traditional CW interference because
they do not divide seconds or kHz on relevant timescales.

Poul-Henning

PS: DCF77 already does SS, but on a second to second basis.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

A couple of comments.
If loran c, I built the simulator for the transmitter and its available at
this website
Index of /simloran http://n4iqt.com/simloran/
But I left out various wave shaping filters because there was no intent to
xmit on the air.
KISS principal after all its all of $29 maybe. But is very optimized to
preserve the accuracy of the 100kc signal and I did check its behaviors with
the real loran stations it matched very well.
Those filters also optimize ground and skywave propagation characteristics
not a problem when the feed is coax and the endpoint the receiver.

Good comments on spreadspectrum. I have to roll back up to the question
asked a while ago. Goals of the interest. From there what frequency might be
chosen and what method of delivery.
Regards

On Tue, Oct 5, 2010 at 6:32 PM, Magnus Danielson <magnus@rubidium.dyndns.org

Hi

Poor, but not poor enough in this case. A quarter wave at 100KC goes pretty deep. If you can drill a well there, you will hit the ground water with your antenna's ground side. The loss in getting there will be just as bad as anything else. Next issue would be stability over a poor ground when it rains.

I suspect that they are going to pull a lot of copper out of the ground at some of the Loran stations.

Bob

On Oct 5, 2010, at 6:16 PM, J. Forster wrote:

Hi

The other answer is that DSP was not really available when the original waveforms were developed. A modern system would not have a "must be able to work with manual delay lines and an oscilloscope" requirement on it.

Bob

On Oct 5, 2010, at 6:56 PM, Poul-Henning Kamp wrote:

In message 60AA6FCF-CF71-4E4C-A7CB-AAB9F11A23BF@rtty.us, Bob Camp writes:

Well, more that LORAN-C was a navigation system primarily intended for
planes, so a high update rate was necessary.

Having established that, and high stability being a component,
Loran-C got (ab)used to also remotely steer clocks of low stability,
for instance in the Nasa Apollo program.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

On 10/05/2010 11:52 PM, Bob Camp wrote:

Well, in the OLD days, Alexanderson extended the antenna using a coil.
That's how the 127 m high antenna towers of Grimeton transmits the 16,7
kHz of 18 km wavelength signal across the atlantic. The modulation was
CW in 80-speed, but anyway. That transmitter has several interesting
features in it for its time... like feed-forward frequency stabilisation.

Cheers,
Magnus

The coil allowed an ok match, but an antenna that is a tiny fraction of a wavelength is going to be inefficient from ohmic loss in the antenna.  You could use a superconductor, but that brings another set of problems (matching networks that also have low loss and can adapt to the changing impedance of the antenna)

On Oct 6, 2010, at 5:30 PM, Magnus Danielson magnus@rubidium.dyndns.org wrote:

Hi

The one thing that an alternator system had available was power. They are fairly efficient and you put lots of horsepower into them. Numbers in the 100's of KW come to mind....

What we're talking about here is more or less a page from the history of radio in the early 1900's. People that were used to the requirements of a VLF system simply didn't believe that a few watts would get very far at "short wave". It took a bunch of crazies to prove them wrong ...

Bob

On Oct 6, 2010, at 8:30 PM, Magnus Danielson wrote:

Bob Camp wrote:

So even if your antenna system were 1% efficient (which would be doing
well) you could still radiate kilowatts.

There was an article in IEEE Proceedings back in the 70s(?) describing
the VLF comm system and what was interesting is that the propagation
losses were quite low (150dB-160dB, I think), the background noise at
the frequency was low, so you didn't need huge radiated powers to make
the system work.  I seem to recall that the big antenna near the Great
Lakes radiated 1 watt, but required something like a megawatt into the
antenna ( a series of buried wires) to get that radiated power.

In the early days of wireless, ships had 500 or 1000 Watt transmitters,
rated by power input to the system. Hence the US amateur radio limit of
1kW DC power to the final stage, so interference was limited.  The
amateurs were limited, the ships have a minimum power requirement.

I think a lot of the astounding performance (to folks at the time) on
200m and down wasn't so much because propagation is better, but because
it's easier to radiate the power efficiently when the frequency goes up.
This was back in the days 20s when the long haul RF links were running
at 10s of kHz

I was surprised to see how late it was before the first wired
transatlantic phone call was made: 1956  ($12/3 minutes, 36 lines
available).  the first Telstar call wasn't that much later in 1962.