Well, FreeBSD had one of the earliest PPSAPI implementations, so its
well tested, and it works extremely well.

Linux still does not have a PPSAPI implementation in the "standard"
kernel. As of 2.6.31, its sort of kinda of halfway there, but not
completely, and I've never been able to get it to work. I'm sure one
can, if ones time in not very valuable.

FreeBSD works right out of the box (okay, you'll need to add the PPS
option to the kernel configuration).

/AWF

Adam,

Adam Feigin wrote:

Actually, one problem is that glibc is (was?) publishing an older
variant of the PPSAPI than the kernel actually supports. This is due to
an unfortunate decission to let kernel-API being made available directly
to be used by applications be declared by glibc rather than following
the kernel. The NTPD finds the glibc variant of the header and uses the
older interface version regardless of the fact that the kernel has
advanced since the glibc took its snapshot out of the early 2.x series.

The correct way would be either to let glibc discover the actual kernel
abilites or just provide the kernel-call wrappers and let the kernel
provide the actual header file.

Usually the glibc approach is correct, but for PPSAPI it is not.
Updating glibc to the current version heals puts a japanese paper wall
in front of the problem, but you haven't properly healed the wound.

To a higher degree things are integrated there in this respect.

Cheers,
Magnus

Thanks for the great information guys.

--
Josh Smith
KD8HRX
email/jabber:  juicewvu@gmail.com
phone:  304.237.9369(c)

On Thu, Oct 1, 2009 at 8:29 AM, Magnus Danielson
magnus@rubidium.dyndns.org wrote:

Bill,

GPS definitely works through a commercial aircraft window.
You have to hold the unit, or at least the antenna, close to the window.
Some airlines, however, prohibit GPS use during flight.
Check with your airline.

Steve Gunsel

At 09:21 AM 10/1/2009, you wrote:

Hello Bill,

I also have a Garmin 60CSx and it worked nicely flying from Amsterdam to
Rovaniemi, Finland (via Helsinki), most of the time about 15 meters
accuracy.
I was sitting at the window seat and just put it in the net from the seat
in front of me (I was sitting 3 times in seats 7A and once in 11A, all on
a Airbus 320) (Just in front and behind the wing).
Sometimes the GPS lost lock (e.g. during banking), I think it would have
performed better if it was in a middle seat, e.g. 7C, or a bit higher.
When I heard the 'lock lost' beep I just picked up the GPS, let it lock
again and put it back in the seat netting.
It worked perfectly in the seat table, but that was not very handy, e.g.
during dinner...

No idea if the GPS reception would behave differently over the Pacific...
I did this to get a complete GPS trace of my holiday to the North Cape, to
be able to geotag my photos (And because it was fun ;-) ).

Greetings,
Pieter.

On 10/1/09 6:56 AM, "Pieter ten Pierick" time-nuts-mail@tenpierick.com
wrote:

, to

And isn't that why we do this stuff?

Lux, Jim (337C) wrote:

Some of us is mostly time-nuts, pos/nav-nuts and maybe just a little
photo-nuts. ;)

But mostly, I think we do stuff like this... because we can. :)

Cheers,
Magnus

Jim,

Jim Palfreyman wrote:

Mmm. Bushwalking is one of your local specialities I gather...

That must have been one jumpy ride... 777 km/hr offroad.

Once again I have been forced to invent a DC fake load to handle the
case where the current sensing of the GPS receiver is set higher than
the hooked in GPS antenna consumes. The shot-from-the-hip solution
involves a T-connector, a 10 uH SMD coil and a 470 Ohm SMD resistor. Not
ideal in any sense, but hopefull pulls enought (additional 10 mA) while
not mocking too much with the signal. A similar approach has worked before.

Cheers,
Magnus

I also once forgot to disable the audible overspeed alarm.... Ideal to stay
discreet...
Jean-Louis Oneto
France

----- Original Message -----
From: "Jim Palfreyman" jim77742@gmail.com
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Thursday, October 01, 2009 3:46 PM
Subject: Re: [time-nuts] GPS from a window seat

the wintec wbt200 data logger, built around the itrax03 seems to have
no trouble with aircraft. haven't had a chance to try my freakishly
sensitive ND100 (MSB2122)

On Thu, Oct 1, 2009 at 10:18 AM, Jean-Louis Oneto
Jean-Louis.Oneto@obs-azur.fr wrote:

--
GDB has a 'break' feature; why doesn't it have 'fix' too?

The only annoyance on my 60CSx is that it reports a bogus altitude
presumably based on the cabin pressure.  To know the true altitude,
one has to go the satellite display and use the menu to get GPS altitude.

Otherwise it works fine in an airplane with a little occasional TLC
to maintain lock.  It even works in a Hercules IF you have a window seat. :-)

David

At 01:18 PM 10/1/2009, you wrote:

In order to fake out some Garmin units, when using them via splitters on
a external antenna, we put 220 ohm resistors from the center of the coax
to the sheild.  The splitters we used were capacitive coupled and this
work fine for the Garmins.

The Garmin units needed to see some sort of DC load, is you wanted to
use the external antenna ports.  If you did not pull any current, the
unit stayed on its internal antenna.

Brian KD4FM

Magnus Danielson wrote:

I used a bias tee with a capacitor block.  I varied the resistor until I
could see signals coming from the external antenna, the built in patch was
shielded with aluminum foil and the receiver verified that no signals were
coming from the internal antenna.  Some receivers needed only a 10K
resistor, some models needed 220 Ohms.

John  WA4WDL

From: "Brian Kirby" kilodelta4foxmike@gmail.com
Sent: Thursday, October 01, 2009 7:57 PM
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Subject: Re: [time-nuts] GPS from a window seat

jmfranke wrote:

In my case I still want it to pass 5 VDC, but let the receiver see some
additional current, so I put a coil in series with the resistor, to not
load the RF too much.

Cheers,
Magnus

Magnus Danielson wrote:

You need to ensure that the coil/inductor doesn't have its first
resonance below 1575.42MHz for an L1 receiver, otherwise it isn't very
effective.
There are some wideband chokes with first resonances well above 10GHz
when mounted correctly.

Bruce

Greg,

I am curious how you determined that WWVB is off the air ?
What receiving rquipment do you use ?
What kind of antenna ?

On NIST's WWVB web site they indicate that it is up and running fine.  I can hear
WWVB on my ham radio set, albeit at a very low level because my antenna is not,
at all, useful down at 60KHz and my tuner will not adjust to that low of a
frequency.

One last point, it does the rest of us no good to say ". . . in my geographical
area . . ." if "we" do not have any idea where the hell that is.  As for the
converter boxes, I cannot address that even though I have a couple around here
someplace.  I do not recall mine showing a date or time, but then again I never
paid much attention to that.

Right now, here in San Diego, California, my date is Oct 1, 2009 and the time is
1956 hours (7:56 pm).

Bill....WB6BNQ

Greg Burnett wrote:

Bruce,

Bruce Griffiths wrote:

As with decoupling capacitors, it is not the actual inductace which is
important as much as adding sufficient of impedance to ensure that the
impedence line does not get a significant reflection.

In my case, I don't get much worse than tossing the 470 Ohm directly
onto the conductor, and that isn't that big deviation even if it is far
from ideal. Shifting in a better inductor is certainly possible. I
needed this one fast, and the system it is for is not into deep sub-ns
timings anyway.

Cheers,
Magnus

On Thu, Oct 01, 2009 at 08:21:28AM -0500, Bill Hawkins wrote:

I have been doing this on and off for years with a now very

antique Garmin IQUE-3600.... not the most sensitive handheld GPS by any
means but if one holds it with the patch antenna facing the window and
tilted up - from a a window seat - it will lock and work fine.  I am
sure it is deaf enough so it won't possibly work from other than right
by the window.  It usually doesn't lock inside buildings even near a
window.

I never had anyone from the airline bother me about doing this

(discretely) UNTIL a recent flight this August from Boston to London
Heathrow on American ... when by chance my wife fainted and passed out
on the floor in the rear galley due to a medication reaction and
dehydration and naturally low blood pressure (she is fine, and has been
told this is very likely harmless and it has happened before, but not on
a plane)... and they called a medical emergency and asked for a doctor
to help if one was aboard and very nearly diverted the plane to Shannon
thinking she had had a heart attack.

I was sitting with my teen aged son in coach and my wife across

the aisle  and down a seat and didn't realize she was the one in trouble

• just that she had gotten up to ask for a glass of water and gone back
  to the rear galley - so when I heard the PA announcement about the
  medical emergency I fired up the Garmin to see where we were (about 600
  miles off the coast of Ireland) and when the chief purser came a couple
  of minutes later to ask me if it was my wife and what medical conditions
  she had he spotted me with the GPS and chewed me out (practically before
  telling me about my wife's situation) saying angrily "using a GPS on a
  plane is illegal".  I checked the AA magazine on the way back to the US
  a week later and it was completely silent on GPSes... not listed as
  allowed and not listed as forbidden - but I was sitting in the middle seat
  of the middle aisle so I had zero chance to even think about trying the
  GPS in any case.

  I do not recall ever seeing a specific prohibition, though
  vaguely defined "radio receivers" are often banned on some airlines.

  Before my VERY frightening episode this summer, the only other
  times I've had any notice from the cabin attendants is maybe one nod
  to put it away when portable electronic devices are supposed to be
  off and stowed.

  I am unaware of any general prohibition on GPS use on airliners...
  I thought I followed this enough so if there were one I'd have heard of
  it, but I haven't.  Of course individual airlines have wide latitude to
  set their own rules (and decide whether to enforce them).

  I have, in fact, used the GPS on the way to and from China over
  the Pacific and it worked fine... it sometimes takes quite a while for
  that antique to lock up when in motion at 650 MPH.... and I have had
  intervals when it didn't find 3 or 4 SVs it could lock on from where
  I was holding it... usually moving it around a bit would cure this,
  especially using its signal strength screen to optimize this.

  I carry and use the thing because I have hated for years to fly
  along looking out the window and not be sure what I was seeing when an
  interesting lake or coastline or island or city goes by... having the
  zoomed out world maps to see this is nice... helps one learn geography
  and geology... and something about air traffic routing.  Most airline
  passenger displays tell you roughly where you are, but rarely show
  enough info to recognize specific landmarks and land features... and
  what that highway is...

  Perhaps the most fun with the thing was riding across France on
  the TGV bullet train and watching it hit 195 MPH on the GPS...  for an
  American that was FAST for a train...

  A final note is that I am sure (though I haven't tried) that it
  should be easy to detect the 1090 MHz Mode S ADS-B GPS position beacons
  with a simple MMIC LNA and diode detector and time stamping box (which
  exist now as a hobby item with a USB interface) and a laptop to decode
  and display the positions on a map.  I can't believe that quite a bit of
  RF from the radar/mode S ATC transponder doesn't get into the cabin and
  the digital messages aren't currently encrypted and do contain the
  plane's position and course and altitude.  Not all planes run ADS-B but
  it is the future of ATC.

--
Dave Emery N1PRE/AE, die@dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in
celebration of what could have been, but wasn't and is not to be now either."

On Thu, Oct 01, 2009 at 08:11:42PM -0600, Greg Burnett wrote:

There is a time of date message stream (TDT) defined for MPEG

transport streams and that and a slightly different version of in the
ATSC variant of MPEG used by US TV stations transmitting digital signals
(now essentially all of them except LPTVs).

Where the data in this comes from depends on the station. Mostly

it originates either in a transport stream multiplexer that feeds the
ATSC modulator or in a separate system that generates PSIP and other
information (a PC perhaps or a dedicated box)...

Both the mux and the PSIP generator likely have the usual

battery backed up clock calendar chip as their default source of time of
day but can be configured to lock this to other time sources within the
station.

Depending on how careful the station is about setting this up it

can of course get unlocked and drift or even set to the wrong time zone
offset or daylight savings versus standard time.

Stations may have their entire plant time and frequency locked

to a GPSDO or Rb or Cesium, but there is no FCC requirement for anything
remotely close to that level of accuracy so many don't.  And stations
may lock time codes and timing of  genlock black burst references to GPS
or may not... and may lock the mux time of day to those or not...

I think the likely explanation of the recent time problem with

converter boxes in the midwest is some common piece of software and/or
hardware used by a number of stations that has a plain old bug with its
timekeeping...

It is true that one network (Fox) supplies more of the over the

air ATSC transport stream than the others (the rest simply send MPEG2
video and audio signals which are decompressed by the satellite IRD and
then re-compressed for the local air by local station equipment - Fox
supplies more or less the exact compressed audio and video the station
is required to transmit on its main channel and controls the device that
makes alterations to this (like inserting a local station logo) from its
master control center.  It is remotely possible that this means that
some of the time of day info for Fox stations originates with the
network or the network controlled splicer device and the network screwed
up and caused a whole region of Fox stations to transmit the wrong time
of day.

Older analog NTSC stuff had an optional vertical blanking

interval messaging system that was used by PBS stations to transmit time
of day and program guide information and many VCRs and DVRs  and some
TVs can look for and find this signal in the vertical blanking interval
of a PBS signal and use it to set time of day.  PBS stations have a box
that generates this data stream and insert it... and depending on
funding and how careful they are it may or may not be locked carefully
to an accurate time source.

I am not sure if it is currently done, but it is possible to

configure MPEG encoders and mux gear to pass these vertical blanking
interval lines in a digital signal including HD versions and some PBS
stations (or even most all) may carry a digitized version of the same
old VBI time data, as they definitely do carry closed caption data in the
VBI for older TVs...

--
Dave Emery N1PRE/AE, die@dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in
celebration of what could have been, but wasn't and is not to be now either."

I have seen receivers needing 180 ohms to switch from internal to external
antenna. It was a slight irritation since the "industry" standard is 200
ohms DC load.

http://gpsnetworking.com/popups/7.htm

http://www.gpssource.com/upload/1x4SpecSheet006.pdf

--

Björn

Hi Bill,

I've done this a few times, with mixed success, using an AMOD AGL3080 GPS
data logger.  I managed to capture an entire flight from HKG to SFO.  That
was from a South facing window seat.  One thing to watch out for is getting
a good solid lock on the ground (e.g. in the boarding lounge) before the
aircraft starts moving.  Once in the air, these units seem to have a lot of
trouble acquiring an initial fix.  On one flight, my unit did not lock for
almost 30 minutes, even though it was switched on as I boarded the
aircraft.  Of course, with a logging unit, you don't have a display, just a
few status lights to let you know if it's working or not.  It isn't until
you're on the ground connected to a computer that you can tell how good the
log is.

A jacket with shoulder pockets, such as a flight jacket, works nicely for
positioning the unit with a view of the sky, if you have a window seat.  An
iPod exercise arm band would be another way to go, but might not be as
inconspicuous.

Good luck!

• Chad.

On Thu, Oct 1, 2009 at 6:21 AM, Bill Hawkins bill@iaxs.net wrote:

Nonsense...unless their own rules prohibit such use, in which case
you are legally obliged to comply.  There is no blanket (ie:
government) rule against them.

It is up to the airline; in the past year I've flown a number of
different airlines.  Some said in their in-flight magazine that GPS
use was allowed, others said it wasn't, and some didn't say anything
at all.

For example, Southwest airlines specifically allows the use of GPS
units:

http://www.spiritmag.com/flightservices/flight-services.pdf

US Airways implies they're OK, but is not explicit:

http://www.usairwaysmag.com/inflight_information/passenger_information/

Either Jetblue or United prohibit GPS', but I cannot find anything on
their websites (they are the other two airlines I've recently flown,
so it's one of them where I saw the prohibition).

No rhyme or reason to it at all.

Tom Frank, KA2CDK
(frequent flyer...and gadget user)

It's so nice that they allow pacemakers "all the time"! I'd hate to think people would have to turn them off for flights...

Why the ban on AM/FM receivers?

-Dave
----- Original Message -----
From: "Thomas A. Frank" ka2cdk@cox.net
To: "Discussion of precise time and frequency measurement" time-nuts@febo.com
Sent: Saturday, October 3, 2009 1:31:08 AM GMT -07:00 US/Canada Mountain
Subject: Re: [time-nuts] GPS from a window seat

Nonsense...unless their own rules prohibit such use, in which case
you are legally obliged to comply. There is no blanket (ie:
government) rule against them.

It is up to the airline; in the past year I've flown a number of
different airlines. Some said in their in-flight magazine that GPS
use was allowed, others said it wasn't, and some didn't say anything
at all.

For example, Southwest airlines specifically allows the use of GPS
units:

http://www.spiritmag.com/flightservices/flight-services.pdf

US Airways implies they're OK, but is not explicit:

http://www.usairwaysmag.com/inflight_information/passenger_information/

Either Jetblue or United prohibit GPS', but I cannot find anything on
their websites (they are the other two airlines I've recently flown,
so it's one of them where I saw the prohibition).

No rhyme or reason to it at all.

Tom Frank, KA2CDK
(frequent flyer...and gadget user)

time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.

I assume it's EMI from the local oscillator.

Is anybody shipping an AM/FM radio that isn't superhet?

--
These are my opinions, not necessarily my employer's.  I hate spam.

On Sun, Oct 04, 2009 at 12:20:26AM -0700, Hal Murray wrote:

FWIW, I have read and been told that there was an era when some

cheap AM/FM radios put out a lot of signal from the LO 10.7 MHz away
from FM stations and that at least a few of them used high side LOs
which would put that LO signal potentially right in the middle of the
band used by VOR navigation beacons and ILS localizers... just above the
FM band from 108-118 MHz.  This would obviously not be good if the
signal power was great enough to interfere with navigation receivers.

The broad rule was put in place because there was no effective

way of determining if any particular radio a passenger might have
radiated or if it even had FM tuning capability.  It was safer just to
ban everything because of those few radios that were way outside of
spec.

--
Dave Emery N1PRE/AE, die@dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in
celebration of what could have been, but wasn't and is not to be now either."

Hi,
This is correct. There was also an issue with harmonics from the local oscillator in the aircraft's own VHF nav/comm receivers blocking the GPS. The answer is a 1575MHz notch filter, e.g. http://www.edmo.com/index.php?module=products&func=display&prod_id=18006
Another problem was bias oscillators in tape players, these could interfere with Omega/VLF receivers. Not a problem now of course. While on the subject of Omega/VLF If you come across a Global GNS-500A OEU box, it has a Efratom FRK Rb in it. There is one on ebay at the moment, item 150257671674, but the price is way to high.
It's very had to predict interference on aircraft. While the probability is low the consequences during take-off and landing are severe. Hence the total ban on electronics during these flight phases. The "illegality" is endangering an aircraft, however you do it. Avionics design is my day job.
 
Robert G8RPI MRAeS

--- On Sun, 4/10/09, David I. Emery die@dieconsulting.com wrote:

From: David I. Emery die@dieconsulting.com
Subject: Re: [time-nuts] GPS from a window seat
To: "Discussion of precise time and frequency measurement" time-nuts@febo.com
Date: Sunday, 4 October, 2009, 8:36 AM

On Sun, Oct 04, 2009 at 12:20:26AM -0700, Hal Murray wrote:

    FWIW, I have read and been told that there was an era when some
cheap AM/FM radios put out a lot of signal from the LO 10.7 MHz away
from FM stations and that at least a few of them used high side LOs
which would put that LO signal potentially right in the middle of the
band used by VOR navigation beacons and ILS localizers... just above the
FM band from 108-118 MHz.   This would obviously not be good if the
signal power was great enough to interfere with navigation receivers.

    The broad rule was put in place because there was no effective
way of determining if any particular radio a passenger might have
radiated or if it even had FM tuning capability.  It was safer just to
ban everything because of those few radios that were way outside of
spec.
   

  Dave Emery N1PRE/AE, die@dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in
celebration of what could have been, but wasn't and is not to be now either."

time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.