Keith,

 

The GPS signal is very weak, and easily blocked/jammed. To avoid such issues, I mounted my GPS antennae (2) on the top of the fuselage, behind the door (IV-P, but the concept is the same on any aircraft). It needs to “see” a large part of the sky at all times, and the area it needs is dependent on the sight line to several satellites, all in different positions at any time. Consider relocating your antenna as a good fix for the sight line issue.

 

Two other considerations: Use RG400 or better cable to connect the antenna to the unit…or the originally supplied cable if you have it. RG58 is not good enough, nor will “TV hookup cable” do the job. Also, CAREFULLY check the antenna gain against the requirements of your unit, and that you are using the correct (active or passive) antenna for your GPS. All of these are potential “gottchas,” but when you finally get it working reliably, it’s a thing of beauty!

 

Good luck,

Bob

 

 

 

The signal reception on my Garmin 420 is really dodgy.  We've tested the unit on a bench and it worked great.  We've swapped the antenna, no change. We swapped the antenna cable, it actually got quite a bit worse (the old one had intermittent issues, the new one is dodgy, nearly full time.)

If I route the cable 'just so', I can make it work fairly well on the ground with the canopy open, but it tends to go to hell when I close the canopy. 

If I unscrew and lift the glare shield about 1/2" - 1", the reception is great.  The GPS antenna is attached to the top of the glare shield on the co-pilot side.

I'm going to get some help from a shop in debugging this...but it seems to me that part of the canopy is either causing interference within the antenna cable, or the antenna itself.

Has anyone experienced anything like this before? This is in a 360.

Keith