What's your the type and length of the cable you have in use?
A second issue might be a to "small" power supply which can drive the preamp into a state of "not functioning as aspected".
Its the Antenna kit from AirNav, so
- RADAR-EXTENDER Antenna
- 1m low loss cable: westflex-103 with N connectors
- Mast pre-amplifier AS-1090
- 10m low loss cable: westflex-103 with N connectors
- AS-1090BT Bias-T for DC-Feed
- 1m cable with BNC/SMA
I've also tried 2 different power supplies, both 12v DC 1.2amp, -ve earth.
The Aerial itself with no PSU is actually working pretty well with no PSU, I'm wondering if the Radarbox itself is supplying some power, or whether if I sort out the pre-amp issue I might get even better results!