The previous owner of my glider installed a TT21. Last July in rural Vermont, a Cessna overflew me on my 6. He was about 100 feet above me.

So I've been thinking that there is a very remote chance that installing ADS-B out might one day be a very big one time pay off for me. I expect that as we get closer to 2020, more and more ADS-B equipped power pilots will rely more and more on their screens and audible alerts for VFR traffic avoidance. I'll probably install ADS-B out eventually, and the cost of the TN72 with the recommended antenna seems reasonable. So the question remains, do I want to spend $300 less and buy a no-name antenna on Amazon?


On Monday, April 3, 2017 at 10:27:03 AM UTC-4, Andrew Ainslie wrote:
a phenomenally expensive $300 plus antenna with it....

I see why it's $300 - after all, it contains an amplifier and yet can handles being exposed to god knows what placed on the outside of an aircraft. But we will no doubt be placing ours somewhere inside where they never get wet. So is there any reason why one can't use this one?

This is missing the point. The TSO'd antenna is tested to comply with the specification. I'd be paying $300 for a quality assurance process and some peace of mind. The price is set by what the buyers will pay, it has little to do with the cost of production. The $300 would seem insignificant if I were paying $6000 to install ADS-B in my aircraft.

The seller of the bargain antenna copied the much sought-after-specification onto the Amazon catalog. He knows a guy, that knows a guy, who makes cheap antennas. Maybe the antenna unit that I buy off Amazon will work as advertised, and maybe it will still be working when I need it. Maybe it will develop a short and brick my TN72. Maybe I will notice and install a new TN72 and an expensive antenna before I really need it. It's all a matter of probabilities. If I'm feeling lucky, then why bother installing ADS-B at all?