Hello Mr. Barton
     
I have spoken with several people at FAA and at ICAO about your 
request and here is what I have learned.

ICAO will not accept a request to assign a downlink number unless it 
comes from the government (FAA in this case) involved.  FAA will not 
send ICAO such a request unless the system is certified by the FAA.  

So the step that that must now be completed is for your system to 
receive FAA certification.  It is recommended by the FAA data link 
(AND-500) office that you contact Mr. Rich Jennings of AIR-130 here at 
FAA HQ to request certification of the system.  Actual certification 
will be done at the regional level, but Mr. Jennings can help you 
begin that process. His telephone number is:  202-267-9897.

Once certification is completed, the FAA will reconsider your request, 
and if it is to be supported, the FAA would present it to the ICAO 
Secondary Surveillance Radar Improvements and Collision Avoidance 
Systems Panel (SICAS Panel) for further consideration.  Both FAA and 
ICAO have assured me that this is the correct process, and in fact the 
only process by which this action can be completed.

Please contact me if you wish to discuss this process further. My 
telephone # is 202-267-7159.  I want to be helpful, so please do not 
hesitate to call.

Duncan Monaco