[time-nuts] WAAS.....

J. L. Trantham jltran at att.net
Thu Jan 9 20:53:43 EST 2014


I have had loss of GPS position on a 'hand-held' unit (Garmin GPSMAP 396)
when flying into PNS.  When I switch to tower frequency (119.9 MHz) the unit
loses its position.  I think it is related to some 'spur' related to the #1
Nav/Com (King KY197) being tuned to that frequency.  If I replace the unit's
GPS antenna with the 'remote' antenna, secured to the windshield, all the
problems go away.

I think it is a 'spur' of the appropriate magnitude when the 'portable'
antenna is still installed.

Joe

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Brian Lloyd
Sent: Thursday, January 09, 2014 8:47 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] WAAS.....

On 1/9/14 12:20 AM, Joe Leikhim wrote:
>
> GPS jamming, intentional or not is pretty serious, and the FCC takes 
> this seriously, but unless you have some pretty hard evidence they may 
> not find it.
In my case my most interesting outage was when I lost all GPS while over the
Atlantic ocean between Haiti and the island of Great Inagua in the Bahamas.
It is a bit difficult to stop and look around while flying at 8,500'. I took
it for a general GPS outage but now I suspect jamming.

When I was living on my boat in the Virgin Islands (I built a WiFi-based
WISP for marinas and anchorages in the USVI) the US Customs interdiction
boat was only about 4 slips away from me. I often talked with the agents
either going out or coming back from "a run". (You do NOT want to screw with
these guys! They are armed to the teeth!) I now realize that they would jam
GPS so that the druggies couldn't get their drops right. (They also admitted
that, most of the time, they couldn't find the drug runners' boats anyway
and figured they got less than 5% of what they were after. So much for the
"War on Drugs.")

The US Coast Guard had (has?) a base on Great Inagua. They run a fleet of
helicopters out of there for ______________ (redacted - read between the
lines). I got a kick how, when they were coming and going, they would
announce their movements to other aircraft using a civil ID rather than
their military flight ID. At this point I suspect I may have been shadowed
and my GPS jammed. Thank god my airplane still had an LF/MF automatic
direction finder (ADF) aboard. I was able to fall back to navigating using
the non-directional LF beacon on Great Inagua. After refueling at Great
Inagua I continued on sans GPS for nearly 100mi when
>POOF< GPS suddenly came back on.

I wonder what the FCC does if it discovers it is another governmental agency
that is doing the jamming? ;-)

I must admit, I like the idea of multi-system sensors that will track GPS,
GLONASS, and (hopefully) Galileo and the Chinese satellite-based navigation
system that is going up. For that matter, is anyone running one of the new
multi-system receivers? I notice that Garmin is selling them as a matter of
course now. The prevalence of jamming might be the reason why.

-- 

Brian Lloyd, WB6RQN/J79BPL
706 Flightline Drive
Spring Branch, TX 78070 USA
brian at lloyd.com
+1.916.877.5067


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