Search the Community

Back in 2014 @JohnB started an excellent post regarding interference issues caused by a failing (external) GPS antenna on his Stratus ADS-B receiver. Specifically a failing external (active) GPS antenna can suddenly cause your CERTIFIED GPS devices to lose satellite reception. The problem can be intermittent or last for considerable periods of time. Experiencing such a failure while on a direct-to route in IMC can be a real nuisance requiring notification to ATC and conversion to alternate methods of navigation. This issue has since been explored more fully (on MS, BT, and elsewhere) and the quick fix while enroute is to simply unplug the external antenna which should restore your panel GPS' functionality. This may or may not be a simple thing to do if your unit isn't readily available in the cockpit (under a seat or on a hat-rack). The folks at Appareo (the maker of Stratus units) have now admitted the existence of the issue and it is noted in their User Manual which states... "WARNING: Avoid pinching or bending the external GPS cable, especially near the antenna. This could damage the cable and cause interference between the antenna and other on-board GPS receivers. The cable’s minimum bend radius is 1 inch." As an avid user of the Stratus units I prefer to place it beneath the pilot seat (out of the sun and out of the way) and I employ both external ADS-B and GPS antennas which provide outstanding reception/coverage. Then I too experienced unexplained simultaneous GPS outages in my certified Garmin navigation equipment (as well as every other GPS receiver in the plane including the iPad and iPhone). At the time I was unaware of the issue described. Thanks to Mr. B and others I was able to discover the issue with some online sleuthing prior to spending large sums of money at the A&P/Avionics shops. So, when I decided to replace my existing (failing) antenna I wanted to look for an alternate, perhaps more robust antenna and began looking at options. As it turns out there are several antenna manufacturers out there with comparable products. The connector is a standard MCX version and I'd always been unhappy with the routing of the stock Stratus (actually AntennaFactor/LinxTechnologies) antenna which employed a straight-out cable. So after some studying and perusing I came to believe that the Garmin GA-25MCX antenna would be a suitable replacement (at half the cost for you CB'ers), and to make matters even better the connector employs a 90 degree fitting which permits much better cable routing in my case. So I bought one to try and am making this post to confirm that it works just fine so far. I've yet to complete in-flight testing with it but in ground testing I found it to pick up a full compliment of satellites without issue (see photo). Let me end by stating that I will monitor it for interference issues and if any arise I will report them here, but it is my understanding that the issue only occurs when the antenna is experiencing a failure of some sort, which mine was. I hope this helps somebody, as Mr. B's post helped me.