[time-nuts] Wildwood NJ ELoran

[Bill Riches]

Here is a dropbox link to Eloran from xmitter at Wildwood, NJ.  I am 10 miles 
away and it is from my hp SA over a long average.


https://www.dropbox.com/s/gxa85mz00z5l0cp/eloran%20dec%208.jpg?dl=0

73,  Bill, WA2DVU
Cape May
-Original Message-


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Re: [time-nuts] eLoran test 6 Feb for almost 2 months

[Poul-Henning Kamp]

In message <20170203214011.76e59406...@ip-64-139-1-69.sjc.megapath.net>, Hal 
Murray writes:

>What does the spectrum look like?  Is that even a reasonable question for 
>that sort of signal?

Look here for some background:  http://phk.freebsd.dk/loran-c

In particular:  http://phk.freebsd.dk/loran-c/theoretical_spectrum/

Newer stuff here:   http://phk.freebsd.dk/AducLoran/

-- 
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Re: [time-nuts] eLoran test 6 Feb for almost 2 months

[Bob Camp]

Hi

The spectrum is about what you would expect from a bunch of short pulses.

http://phk.freebsd.dk/loran-c/theoretical_spectrum/

Bob


> On Feb 3, 2017, at 4:40 PM, Hal Murray  wrote:
> 
> 
> kb...@n1k.org said:
>> the signal shows up over many 10’s of KHz of  bandwidth each side of 100
>> KHz.
> 
> What does the spectrum look like?  Is that even a reasonable question for 
> that sort of signal?
> 
> How well do typical old/analog spectrum analyzers work on that sort of 
> signal?  (as compared to modern digital/FFT versions)
> 
> How many samples do you need to get the full picture with a FFT?
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] eLoran test 6 Feb for almost 2 months

[Hal Murray]

kb...@n1k.org said:
> the signal shows up over many 10’s of KHz of  bandwidth each side of 100
> KHz.

What does the spectrum look like?  Is that even a reasonable question for 
that sort of signal?

How well do typical old/analog spectrum analyzers work on that sort of 
signal?  (as compared to modern digital/FFT versions)

How many samples do you need to get the full picture with a FFT?

-- 
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Re: [time-nuts] eLoran test

[paul swed]

John thats right and the extra bit is the data channel.
Though your homebrew receive may detect and lock. There is only 1 site so
you can't actually navigate. They fake the receivers out by having the same
transmitter act like two.
Regards
Paul
WB8TSL

On Fri, Feb 3, 2017 at 12:58 PM, John Ponsonby 
wrote:

> I have a three channel LORAN-C receiver of my own design which I made over
> thirty years ago. I built it for navigating my small yacht. I think the
> eLoran signals are compatible though of course my receiver doesn't have the
> means to extract the data channel.
> Here follows a brief tutorial.
> All LORAN-C stations transmit on 100kHz precisely. The signals come in
> groups of eight pulses spaced precisely 1ms apart. Master stations transmit
> a ninth identifying pulse spaced 2ms after the last of the 8 so they look
> like: {  ●} The phase of the RF is switched between 0° and 180°
> according to a fixed pseudo-random pattern from pulse to pulse. There are
> two phase patterns, the A pattern and the B pattern, and these alternate
> from one 8 pulse group to the next. The Master patterns are different from
> the Secondary patterns. Each LORAN-C chain has its own GRI (Group
> Repetition Interval) and this is the number of ten's of μs from the start
> of one 8 pulse group to the start of the next.
> For precise navigation one needs to lock onto the ground-waves. If the
> receiver is far from a transmitter the skywave can arrive very shortly
> after the ground-wave, so it is essential to only use the start of each
> pulse. Officially one is supposed to lock onto the third positive going
> zero crossing point on the rising edge of each pulse. Close to a
> transmitter the skywave can arrive up to 1ms after the ground wave so that
> it interferes with the start of the next pulse. The phase coding is
> designed to avoid this causing trouble. The skywave delay varies with time
> of day as the ionosphere goes up and down.
> Because the wavelength is so long (3km), the near-field of the transmitter
> extends quite a long way. That has the effect of changing the phase of the
> received signal from what one might first think it would be assuming a
> fixed velocity of propagation.  The velocity of propagation is less than
> the free-space velocity of light and is different between over-sea and
> over-land paths.
> My receiver just gives two relative time delays in μs and I used a TI59
> calculator to convert to latitude and longitude. The program only just fits
> within the capacity of the calculator.
> I don't know anything very specifically about eLoran but I think the main
> modification is to add extra phase coding on the pulses to form the data
> channel.
> John Ponsonby
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Re: [time-nuts] eLoran test 6 Feb for almost 2 months

[Poul-Henning Kamp]

In message <589490f1.4090...@erols.com>, Chuck Harris writes:

>All Loran C signals are transmitted at precisely 100.0... KHz.

Actually, they're not.

The envelope changes the frequency in rather interesting ways.  I used
to have a plot of it, but it seems to have disappeared into my
archives some time go...

Stick to the zero-crossings.

-- 
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Re: [time-nuts] eLoran test 6 Feb for almost 2 months

[Poul-Henning Kamp]

In message 
, paul swed 
writes:

>John absolutely 1 frequency 100 KHz. The repetition rate is 89700 us. Its
>pulse and you need about +-15KHz BW. If listening its just a ticking sound.

Instead of your SDR it might be smarter to use either a digital
oscilloscope or spectrum analyzer.

You will need a frequency of *exactly* 1/0.089700 us = 11.14827201... Hz.
(HP5359A's are *great* for this, but most DDS sig-gens will work too.

You use this to signal to trigger your scope/spectrum analyzer, feed the
antenna signal to the input and select averaging mode.

If you have a really good antenna signal and a scope/spec-an with high
X-resolution, you can halve the sync frequency and, so that the pulse
polarity does not cancel out about half the loran pulses.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@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.
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Re: [time-nuts] eLoran test

[John Ponsonby]

I have a three channel LORAN-C receiver of my own design which I made over 
thirty years ago. I built it for navigating my small yacht. I think the eLoran 
signals are compatible though of course my receiver doesn't have the means to 
extract the data channel. 
Here follows a brief tutorial.
All LORAN-C stations transmit on 100kHz precisely. The signals come in groups 
of eight pulses spaced precisely 1ms apart. Master stations transmit a ninth 
identifying pulse spaced 2ms after the last of the 8 so they look like: 
{  ●} The phase of the RF is switched between 0° and 180° according to 
a fixed pseudo-random pattern from pulse to pulse. There are two phase 
patterns, the A pattern and the B pattern, and these alternate from one 8 pulse 
group to the next. The Master patterns are different from the Secondary 
patterns. Each LORAN-C chain has its own GRI (Group Repetition Interval) and 
this is the number of ten's of μs from the start of one 8 pulse group to the 
start of the next.
For precise navigation one needs to lock onto the ground-waves. If the receiver 
is far from a transmitter the skywave can arrive very shortly after the 
ground-wave, so it is essential to only use the start of each pulse. Officially 
one is supposed to lock onto the third positive going zero crossing point on 
the rising edge of each pulse. Close to a transmitter the skywave can arrive up 
to 1ms after the ground wave so that it interferes with the start of the next 
pulse. The phase coding is designed to avoid this causing trouble. The skywave 
delay varies with time of day as the ionosphere goes up and down.
Because the wavelength is so long (3km), the near-field of the transmitter 
extends quite a long way. That has the effect of changing the phase of the 
received signal from what one might first think it would be assuming a fixed 
velocity of propagation.  The velocity of propagation is less than the 
free-space velocity of light and is different between over-sea and over-land 
paths.
My receiver just gives two relative time delays in μs and I used a TI59 
calculator to convert to latitude and longitude. The program only just fits 
within the capacity of the calculator. 
I don't know anything very specifically about eLoran but I think the main 
modification is to add extra phase coding on the pulses to form the data 
channel.
John Ponsonby 
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Re: [time-nuts] eLoran test 6 Feb for almost 2 months

[paul swed]

John absolutely 1 frequency 100 KHz. The repetition rate is 89700 us. Its
pulse and you need about +-15KHz BW. If listening its just a ticking sound.
Ruslan
NH will be easy to pick it up. The core frequency is 3 Cesiums in a cluster.
As for time transfer it can but its really a pain in the backend and that
information is indeed in the data channel.
So make us jealous with your CS and RBs. :-)
I am down in Franklin Ma so we are actually close compared to others.
Regards
Paul
Swedberg

On Fri, Feb 3, 2017 at 2:08 AM, Ruslan Nabioullin 
wrote:

> On 02/02/2017 09:47 PM, paul swed wrote:
>
>> Ruslan,
>> Seems to be backward compatible. Yes.
>> All of my stuff works austrons and SRS 700.
>> Whats your location? The transmitter is in NJ and I am near Boston. So
>> somewhat close for me. My antenna is the standard boat preamp and whip
>> antenna. 6 foot off the ground.
>> Regards
>> Paul
>> WB8TSL
>>
>
> Very exciting news!  I and my modest metrology lab is located in southern
> NH.  But time transfer won't work, right?  I'm not interested in
> LORAN-based frequency transfer due to my having a number of modern Cs
> standards, Rb standards, a disciplined OCXO standard, and currently one
> low-end (+/- 150 ns) GPS time and frequency receiver (the XL-AK).
>
>
> -Ruslan
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Re: [time-nuts] eLoran test 6 Feb for almost 2 months

[Bill Riches]

100 khz.

73,

Bill, WA2DVU

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of John Marvin
Sent: Friday, February 3, 2017 1:21 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] eLoran test 6 Feb for almost 2 months

I don't have a Loran receiver, and I live in Colorado. But I'd still like to 
check late at night to see if I can see a signal on my SDR receiver. I tried 
looking at old posts, and did some research online, but the best I can tell is 
that Loran C (and I assume eLoran) is transmitted at around 100 Khz. Anyone 
know precisely what frequency(s) are used by the Wildwood eLOran station?

Regards,

John


On 2/2/2017 11:59 AM, paul swed wrote:
> Well this is nice almost a 2 month long test.
> So if you thought about seeing if you could receive eLoran on your 
> Loran C receiver this is a good opportunity. With respect to the data 
> channel pretty sure none of the receivers we have know or care about it.
>
> The Wildwood, NJ eLoran transmitter will be continuously broadcasting 
> from
> 0900 (EST) on 06 February 2017 through 1200 (EST) on 31 March 2017.
> Wildwood will be broadcasting as 8970 Master and Secondary most of the 
> time but occasionally may operate at other rates.
>
>
>
> Please note that the Loran Data Channel (LDC) will be undergoing 
> testing and may be unavailable or unreliable for short periods of time
>
> from 06-10 February 2017.
>
> Regards
> Paul
> WB8TSL
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Re: [time-nuts] eLoran test 6 Feb for almost 2 months

[Bob Camp]

Hi

Loran C is a pulse based system. All transmitters world wide run on the same 
100 KHz frequency. The thing that 
distinguishes one transmission from another is the repetition rate of the 
signal. If you have a spectrum analyzer
and hook up a piece of wire near one of the transmitters, the signal shows up 
over many 10’s of KHz of 
bandwidth each side of 100 KHz. With reasonable gear, you can pick up the 
European Loran chains in the US
on a regular basis. You can also pick up the Russian system that runs on the 
same frequency. The gotcha there
is that you are looking at “skywave” rather than “ground wave” signals to some 
degree. That degrades their value
for timing or for navigation. (Yes, it is all a lot more complicated that than 
very simple / quick summary). 

Bob

> On Feb 3, 2017, at 1:20 AM, John Marvin  wrote:
> 
> I don't have a Loran receiver, and I live in Colorado. But I'd still like to 
> check late at night to see if I can see a signal on my SDR receiver. I tried 
> looking at old posts, and did some research online, but the best I can tell 
> is that Loran C (and I assume eLoran) is transmitted at around 100 Khz. 
> Anyone know precisely what frequency(s) are used by the Wildwood eLOran 
> station?
> 
> Regards,
> 
> John
> 
> 
> On 2/2/2017 11:59 AM, paul swed wrote:
>> Well this is nice almost a 2 month long test.
>> So if you thought about seeing if you could receive eLoran on your Loran C
>> receiver this is a good opportunity. With respect to the data channel
>> pretty sure none of the receivers we have know or care about it.
>> 
>> The Wildwood, NJ eLoran transmitter will be continuously broadcasting from
>> 0900 (EST) on 06 February 2017 through 1200 (EST) on 31 March 2017.
>> Wildwood will be broadcasting as 8970 Master and Secondary most of the time
>> but occasionally may operate at other rates.
>> 
>> 
>> 
>> Please note that the Loran Data Channel (LDC) will be undergoing testing
>> and may be unavailable or unreliable for short periods of time
>> 
>> from 06-10 February 2017.
>> 
>> Regards
>> Paul
>> WB8TSL
>> ___
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>> and follow the instructions there.
> 
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Re: [time-nuts] Distribution amplifier (again!) - now mostly ok but has gain peaking

[Mattia Rizzi]

Hello David,

>200ps of skew is consistent with long traces on board material like
standard FR4 because of uneven dielectric constant

Can you elaborate it? What do you mean by "long traces"?
I saw the PCB done by Anders, the track length is about 10 cm. Using the
microstrip formula, even for a big dielectric change (Dk from 4 to 4.6,
worst scenario), the propagation speed change is about 5% (30ps).
Indeed, you'll get also reflections, but the effect is dwarfed by the "s"
done by Anders for length matching.
My gut-feeling is that most of the 200ps skew (80-85%) is coming from
74AC04's unmatched outputs, but since two persons already replied
suggesting PCB issues, I'm very interested.

cheers,
Mattia


2017-01-29 8:11 GMT+01:00 David :

> On Sat, 28 Jan 2017 13:58:27 +0200, you wrote:
>
> >...
> >
> >The picture gallery also shows a pulse distribution amp for 1PPS. It has
> an
> >LT1711 comparator feeding an 74AC14 buffer with length-matched traces to
> >74AC04's at the outputs. So far my length-matching didn't give zero
> >output-skew between the outputs - I see around 150-200ps skew which I
> tried
> >to tune a bit with wires and 0R resistors - without very much success..
> any
> >ideas for improving this - or just leave it at 200ps skew?
> >
> >cheers,
> >Anders
>
> 200ps of skew is consistent with long traces on board material like
> standard FR4 because of uneven dielectric constant produced by uneven
> fiberglass weave.  One way to ameliorate this is to route traces at a
> diagonal compared to the fiberglass weave.
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Re: [time-nuts] eLoran test 6 Feb for almost 2 months

[Chuck Harris]

All Loran C signals are transmitted at precisely 100.0... KHz.

They are a pulse signal system, where each member of the chain uses
a different repetition rate to time the placement of its pulses.

The repetition rates are designed so that they pulses from any
two chains are not coincident, but for random times, over very
long intervals.

There are numerous Wiki's, and other sources of information that
can be found by searching for Loran C.

-Chuck Harris

John Marvin wrote:
> I don't have a Loran receiver, and I live in Colorado. But I'd still like to 
> check
> late at night to see if I can see a signal on my SDR receiver. I tried 
> looking at old
> posts, and did some research online, but the best I can tell is that Loran C 
> (and I
> assume eLoran) is transmitted at around 100 Khz. Anyone know precisely what
> frequency(s) are used by the Wildwood eLOran station?
> 
> Regards,
> 
> John
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Re: [time-nuts] eLoran test 6 Feb for almost 2 months

[Ruslan Nabioullin]

On 02/02/2017 09:47 PM, paul swed wrote:

Ruslan,
Seems to be backward compatible. Yes.
All of my stuff works austrons and SRS 700.
Whats your location? The transmitter is in NJ and I am near Boston. So
somewhat close for me. My antenna is the standard boat preamp and whip
antenna. 6 foot off the ground.
Regards
Paul
WB8TSL


Very exciting news!  I and my modest metrology lab is located in 
southern NH.  But time transfer won't work, right?  I'm not interested 
in LORAN-based frequency transfer due to my having a number of modern Cs 
standards, Rb standards, a disciplined OCXO standard, and currently one 
low-end (+/- 150 ns) GPS time and frequency receiver (the XL-AK).


-Ruslan
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Re: [time-nuts] eLoran test 6 Feb for almost 2 months

[John Marvin]

I don't have a Loran receiver, and I live in Colorado. But I'd still 
like to check late at night to see if I can see a signal on my SDR 
receiver. I tried looking at old posts, and did some research online, 
but the best I can tell is that Loran C (and I assume eLoran) is 
transmitted at around 100 Khz. Anyone know precisely what frequency(s) 
are used by the Wildwood eLOran station?


Regards,

John


On 2/2/2017 11:59 AM, paul swed wrote:

Well this is nice almost a 2 month long test.
So if you thought about seeing if you could receive eLoran on your Loran C
receiver this is a good opportunity. With respect to the data channel
pretty sure none of the receivers we have know or care about it.

The Wildwood, NJ eLoran transmitter will be continuously broadcasting from
0900 (EST) on 06 February 2017 through 1200 (EST) on 31 March 2017.
Wildwood will be broadcasting as 8970 Master and Secondary most of the time
but occasionally may operate at other rates.



Please note that the Loran Data Channel (LDC) will be undergoing testing
and may be unavailable or unreliable for short periods of time

from 06-10 February 2017.

Regards
Paul
WB8TSL
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