[time-nuts] MH370 Doppler
albertson.chris at gmail.com
Wed Aug 20 20:32:44 EDT 2014
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
At 1.6GHz one part per billion is 1.6Hz. 175Hz of shift gives
something like a 2,400 mile radius ring.
On Wed, Aug 20, 2014 at 8:47 AM, Joe Leikhim <jleikhim at leikhim.com> wrote:
> 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 hz_.
> I think we can discount the error being that large, but could still
> rationalize it being a significant portion of the reported BFO value./
> Also the ground track is unknown, they are attempting to reconstruct the
> ground track from the BFO (Burst Frequency Offset "Doppler") and from the
> BTO (timing pings) the BTO supposedly offers range information, hence the
> concentric rings corresponding to pings._
> _Chris Alb__ertson wrote:_
> "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. But maybe the effect is only about 50 feet on
> the ground.
> The OCXO error of even 1E-5 is just not very important as it does not
> move the aircrafts ground track enough to matter."
> Joe Leikhim
> Leikhim and Associates
> Communications Consultants
> Oviedo, Florida
> JLeikhim at Leikhim.com
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