13.99 – ADS-B in antenna

This entry is part 65 of 67 in the series 13 - Electrical / Instruments

For ADS-B in, I’m going somewhat old-school.  While I could have gone with an installed ADS-B receiver and displayed the output on the Grand Rapids EFIS, I don’t like that approach.  I like having weather on a device other than my PFD.  And displaying it on the co-pilot EFIS would have it too far away for my taste.

Currently, I use an iPad with Foreflight for charts, approach plates, weather and traffic.  A Stratus II provides ADS-B weather and traffic. And I like it that way.

But I’ve been unhappy with the reception performance of the Stratus internal antenna. They sell an external antenna, but it’s $70 and probably would only be marginally better.

I exchanged some email with Jim Weir of RST Engineering (his manual is what I’ve used when building antennas). He gave me the spec’s for building an external antenna for the Stratus II.  Basically, it’s two 3″ legs. The real shocker was the connector that is used to connect to the Stratus.  It’s an unusual, tiny-ass connector and the best price that I could find was $17! (normally, coax connectors are around $1-4)

Once it came in, I donned the magnifying headset and terminated the RG-174 cable to the unbelievably expensive Hirose connector. Then I decided to run a little test.  Before installing the foil antenna and connecting the coax to it, I separated the shield from the center conductor and used duct tape to attach it to the side of the fuselage just aft of the instrument panel.


I went up and checked the reception status and this is what I saw using the internal antenna:


Receiving from four towers and one was showing a 51% error rate.  This is actually pretty good compared to what I normally see. Then I connected my new, test antenna. Unfortunately, I didn’t get a screenshot, but it was showing 5 towers and all had 0% error rate!

So now I’m debating whether to go to the trouble of building the the foil antenna and just sticking this one behind the panel.

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