[time-nuts] WAAS.....

[Brian Lloyd]

On 1/9/14 7:53 PM, J. L. Trantham wrote:
> 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.
Before a panel-mount GPS in an airplane may be used for IFR (instrument) flight
it must be tested with the comm radios set to a number of harmonically-related
frequencies to ensure there is no interference with the GPS signal and then
signed off.

So, yes, it is very likely a harmonic of one of your comm radios was jamming the
GPS.

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