[time-nuts] Boeing 787 GPS reception trouble

[nuts]

On Mon, 2 Jun 2014 20:18:00 +0100
"Bill Woodcock" <woody at pch.net> wrote:

> 
> I'm posting this from inside an Ethiopian 787, on the ground, with
> the doors closed.  I just completed a fifteen-minute voice call
> initiated from inside the plane, with reasonable reception and no
> drops, while the doors were open.  And I was able to get a new GPS
> location in less than two seconds (though that wasn't from cold boot,
> so I don't know whether it was able to accelerate the process using
> cached data previously received). The phone (an iPhone 5S) is showing
> three bars inside the plane, and was varying between three and four
> bars outside. Note that the non-linear mapping of signal strength to
> "bars" is a matter of intense negotiation between carriers and
> vendors, and shouldn't be taken as a literal indicator of anything at
> all.  Likewise, Ethiopian may have ordered planes with significantly
> different options than ANA (no center overhead storage in business,
> for example) and used different paint formulation. 
> 
> Nevertheless, in this specific case, I'm not seeing anything that
> seems out-of-the-ordinary relative to other aircraft. 
>                 -Bill

You probably know this, but just in case, cell phone GPS is assisted,
i.e. AGPS. It uses tower information to assist in lock. [Also data, as
many a roamer has found out when billed. On an iphone, the saving
grace is it has real problems with APN settings, so often it won't use
the assist when roaming.] 

I recall my GSM phone making some RF burps once when I was using it
in the desert where there was no cellular service. But the poster that
said the phone would listen before transmitting has a good point, so I
need to repeat this experiment sometime. I was using a spectrum
analyzer and picked up my phones chirping. 

Regarding radiation, I've used my Geiger counter at mile high altitudes
in Nevada and never got a count per second, even with the gamma shield
not used. You can look at the DOE CEMP stations:
http://www.cemp.dri.edu/
Some of the radiation monitors are not working, but this one is and it
has typical readings of 15uR/hr.
> http://www.cemp.dri.edu/cgi-bin/cemp_stations.pl?stn=rach

As a crude estimate, 1000CPM = 1mR/hr, or 1CPM = 1uR/hr. So I suspect
the 60CPM received in Colorado is use to local radiation rather than
cosmic rays. 

My Ludlum isn't calibrated, but I've compared it to one from the DOE
using their source and it matched close enough for government work.