[time-nuts] GPS from a window seat

[Mark Spencer]

I'd also think twice before using a shortwave receiver on a comercial air craft (:  I'd be worried about the emissions from the various local oscilators interferring with the HF and VHF radios on board the air craft. 

Many years ago I used to use a portable sony shortwave receiver as a simple signal generator for making go / no go checks on UHF receivers.   It's local oscilators put out easily detecable harmonics thru 470 Mhz.

Regards
Mark VE7AFZ


 


----- Original Message ----
From: "Lux, Jim (337C)" <james.p.lux at jpl.nasa.gov>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Sun, October 4, 2009 2:21:22 PM
Subject: Re: [time-nuts] GPS from a window seat



> 
> But that doesn't change the fact that if a drunk businessman or a
> bored 6 year old with a new toy can stealthily endanger all the
> passengers on a plane, the responsibility - and liability - should be
> with the aircraft designer.
> 
> Bringing it back to the normal topic at hand, I wonder - if you had a
> radio receiver tuned to WWV, and a GPS with a 1pps, if you could see
> the relativistic effect of flying at 500 knots at 30K feet and log it
> on your computer?

500 kts = about 250 m/s.
C^2 = 9E16 m^2/s^2
V^2/C^2 = 6.2E4/9E16 = .6E-12

A pretty small thing to look for


Uncertainty in frequency from WWV due to ionospheric issues is on the order
of 0.1 to 1 Hz. Call it about 0.1 ppm for the 10 MHz signal.

Doppler effect on frequency from WWV is 2.5E2/3E8 = 1E-5 (10 ppm), which is
orders of magnitude larger than anything else you're going to see.


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