Yes, we are "on the same channel"..

The company that lease you the 5khz BW have already receivers for that portion of the L band. They are used for the different purposes and service but the hardware is there. The problem is that this receivers (in some case transcievers) are not cheap.

This arejust my thoughts and I may be well wrong but you may get maybe some idea from this:

Complete receiver based on the present RTL8232 architecture and R820T tuner with extra LNA+filter and antenna can be build for 20$. You will need a descent RF engineer to pack everything together and a mass production in China. Only then you can meet the 20$ price.

If I will have to design this system, I will go with the complete unit on the antenna, so the receiver, LNA and filter should be on the back side of the antenna reflector made from double sided laminate. The other (ground side of the laminate will be the ground for the electronics and at the same time the reflector of the patch antenna. To get the maximum gain with the patch antenna I will use the air as dieletric, hense the biggest aperture and the max possible gain with the round patch rather than the square patch. If the circular polarisation is required, then the patch should be`circulary polarised. Using this approach the 9.5dBi can be accomplished. If the size is not so important, two of the paches can be stacked (double size antenna) where you will get some 2.5dB in real world on top of the 9.5dBi resulting 12dBi antenna. All that can be packed in the low profile plastic radome (something like WiFi panel antenna) and just a USB plug on the complete unit. Of course, the connector for the aux antenna is wellcome. This can be simple and cheap F connector.

You may get connected with the guys producing the latest dongle clones that we have in the market, they can do this job....