@fatherdoctor you may need a filter.
Look at the stats for BellCountyTX flightaware.com/adsb/stats/user/BellCountyTX
He has the same antenna with a filter on a 40ft tower in a what I believe is a rural area in Texas (85% of his reports are greater then 60 miles away).
Pics are in this port ads-b-flight-tracking-f21/pre-amps-vs-low-loss-t36637.html
He had to add a filter due to nearby pagers (and maybe cell towers)
Note that he has a old Raspberry Pi 1B. The model with 2USB ports and 256MB ram. He said it runs at 100% CPU as soon as he puts it up on his tower.
I suspect he would be more hits with an RPI2 (4 times more memory and 2+ times better CPU).
Your coax should only add about 1-1.5db loss (around 10db per 100ft for lmr240)