[time-nuts] MH370 Doppler

Chris Albertson 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
ring.

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
>
> 407-982-0446
>
> WWW.LEIKHIM.COM
>
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-- 

Chris Albertson
Redondo Beach, California



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