Joe Leikhim jleikhim@... writes:
I raised this on the Duncan Steel website and was pretty much blown
off.
Oh there is a nice stable OCXO aboard etc.
Well DUHH yes there is an OCXO aboard and if it is good to -20 to
+75C,
or just -20 to +60C and there is a huge fire raging around it
In message 53f8060b.7020...@leikhim.com, Joe Leikhim writes:
I applaud those applying their rather extensive math skills at
this problem, but from the outside, it appears to me that the problem
is so very complex (error prone) and so many assumptions are being
applied, that folks time
Joe,
I did find it here:
http://www.dca.gov.my/mainpage/MH370%20Data%20Communication%20Logs.pdf
There is also some Inmarsat presentation giving a little more detail.
At the same time, the data gathered is from a system not designed for
navigation and positioning purposes. It gives a rough
Time-error would be rings for sure.
Doppler errors could also behave with these rings, but there is a much
more complex scenario of ground speed and angle of observation. As the
transponder passes under the satellite-earth line there is no
observeable doppler, just like a train passing by has
You can probably find links to all of the data from the Duncan Steel Blog.
You might start by looking at the questions the group has posed in an open
letter to the ATSB and Inmarsat. Frankly, the data Inmarsat released appear to
be rather scant and some believe to be doctored not RAW.
I
The L Band uplink was reported to be transmitting at around 1.6435/ghz.
/
Assuming, we actually knew what the tolerance of the OCXO (If it is an
OCXO) was under the environment of the mishap, and assuming it /was/
10ppm for example. The error would be (1,650 X1,000,000) * 10ppm or
_16,500
Yes, that is what they are doing. A given Doppler shift corresponds
to a certain ring on the Earth's surface. Each Hertz of Soppler
shift corresponds to a certain number of miles on the radius of the
ring.
At 1.6GHz one part per billion is 1.6Hz.175Hz of shift gives
something like a 2,400
My understanding is that the BFO and BTO values are self reported from the SDU
(Terminal in the aircraft) and they represent adjustments made by the SDU. If
so the BFO value would be the AFC adjustment relative to the OCXO onboard. My
contention is that if the investigators are assuming the
As I understand it, Doppler will give you the magnitude of the velocity
vector for an aircraft with respect to the satellite, but it won't give
you the actual direction of the aircraft.
Why does the stability of the oscillators matter if you can't determine
the direction? Is there another
You CAN determine the ground track if you assume the altitude above
sea level is constant and the aircraft's speed is also constant. But
you are correct that Doppler alone would not be enough.
The question I have to people here is: How does error in the dopler
translate to error in the ground
On Tue, Aug 19, 2014 at 12:08:24PM -0400, Joe Leikhim wrote:
My understanding is that the BFO and BTO values are self reported from the
SDU (Terminal in the aircraft) and they represent adjustments made by the
SDU. If so the BFO value would be the AFC adjustment relative to the OCXO
I raised this on the Duncan Steel website and was pretty much blown off.
Oh there is a nice stable OCXO aboard etc.
Well DUHH yes there is an OCXO aboard and if it is good to -20 to +75C,
or just -20 to +60C and there is a huge fire raging around it for an
hour, and then perhaps later the
The total Doppler in this case is on the order of 100 Hz. The tiny
frequency shifts of an out of spec OCXO is just to small to measure.
The data says at UTC 18:30 the shift was in the mid range and was
about 175Hz. Assume the OCXO drifts 10 parts per million. That
is a lot for an OCXO.
Is anyone paying attention to all the chatter about the lost aircraft
MH370, Inmarsat's supposed flight tracks based on 6 or 7 pings (1 per
hour), the Doppler shift (BFO) and transaction timing (BTO) etc??
Basically from my perspective they are putting too much stock into the
Doppler which
I thought that Inmarsat terminals had AFC to the sat's down-link. Not to the
degree of true phase-lock like DSN has but enough so that the sat's abillity to
do doppler correction on the uplink is valid to help with BER, etc... Otherwise
the doppler correction would be of no help and not be
On Mon, Aug 18, 2014 at 04:18:30PM -0400, Brian, WA1ZMS wrote:
I thought that Inmarsat terminals had AFC to the sat's down-link. Not
to the degree of true phase-lock like DSN has but enough so that the
sat's abillity to do doppler correction on the uplink is valid to help
with BER, etc...
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