Trees and SDR gain values

FlightAware ADS-B Flight Tracking
1

Random comment.

My SDR reports these values as supported:
"Supported gain values (29): 0.0 0.9 1.4 2.7 3.7 7.7 8.7 12.5 14.4 15.7 16.6 19.7 20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 40.2 42.1 43.4 43.9 44.5 48.0 49.6 "

For a few months, I’ve been running around 44.5 to keep the 3db ratio around 2 to 3.

Lately, I had to drop it down to 32.8 to get it below 3.

My FA antennae is on my roof but I have very tall trees around my house. Starting to wonder if a 50ft pole would be worth it when the leaves come back.

2

Leaves love microwave and absorb them almost entirely.

Incresing the height of your antenna will increase your maximum range till the antenna reaches a hight slightly above the height of obstructions (neighbor’s houses, tall buildings, tall trees). This height is is optimal as further increase is a huge investment of money, effort, and time, without propotionate benefit in terms of maximum range or number of plane.

Conclusion: don’t use too high a pole. Use only a pole which is just slightly higher than the tallest trees.

3

… don’t know whether you have an amplifier between antenna and usb-dongle. but if not - and using a passive antenna - i’d suggest first another test for better results. at least at my site i got much more data when going above -3db with gain value ‘-10’ a.k.a. ‘agc’

tom