There is no requirement to inform ATC about your takeoff alternate. You have to determine for yourself if you need one or not according to the wx minimum you need to fly an OEI approach. In our company if we need one the takeoff alternate is stated on our operatioal flight plan. You have to be able to reach it within 1 hour OEI cruising speed and the wx there has to be within your limits for ETA +/- 1 hour.
Some airplanes are able to perform an OEI CAT IIIa approach like the SAAB 2000 using the head up display. So in this case you do not even need a takeoff alternate!
The procedures in case of com failure are clearly stated in the emergency section of Jeppesen (communications). So in case 7600 appears on the screen of the controller he knows exactly what you are going to do (if you read the appropriate section....).