Yes, 'have noticed that. But I’m not sure, if the N-BNC-adapter or the BNC-plug of the antenna cable are really good sealed from water ingress or snow & ice in winter …
For a nice DIY-‘radome’ look also here ==> http://discussions.flightaware.com/ads-b-flight-tracking-f21/shorting-a-spider-antenna-t35565.html …
… anyway, the 5/8 antenna looks some more ‘professional’ 8)