@tsunami My setup is max 50m radius and 433MHz standard power RFM69s so a small 1/4 wave whip works reliably even from a below ground pump chamber 10m away. Your 915MHz at 200m SHOULD work on 1/4 wave if obstacle free line of sight, but you could try a 2.4GHz Wifi router at one location and use a mobile at the other to test if you can see the router. I can see at least 3 neighbouring routers identified on my mobile from over 40m away through masonry, 10 on the laptop, so it's a simple enough test. If you can see the router on either, 915MHz should be rock solid with a simple whip and no need of directional antenna.