Carrier Aggregation (CA) is a technique used in 5G and previous cellular generations to temporarily increase the data rate of a specific user during peak demand periods or to reduce carrier congestion. CA is achieved by combining two or more carriers and providing a virtual, wider overall bandwidth to high-demand users of the system. CA was introduced in the 4G/LTE wireless era and has been proven effective in 5G as well, where it is said to play a significant role in efficient network capacity management. Given this success, the satellite communication (SatCom) community has put its attention into CA and the potential benefits it can bring in terms of better spectrum utilization and better meeting the user traffic demand. While the theoretical evaluation of CA for SatCom has already been presented in several works, this article presents the design and results obtained with an experimentation testbed based on Software Defined Radio (SDR) and a satellite channel emulator. We first present the detailed implementation design, which includes a Gateway (GW) module responsible for PDU-scheduling across the aggregated carriers, and a User Terminal (UT) module responsible for aggregating the multiple received streams. The second part of the article presents the experimental evaluation, including CA over a single Geostationary (GEO) satellite, CA over a single Medium Earth Orbit (MEO) satellite, and CA combining carriers sent over GEO and MEO satellites. A key contribution of this work is the explicit consideration of multi-orbit scenarios in the testbed design and validation. The testing results show promising benefits of CA over SatCom systems, motivating potential upcoming testing on over-the-air systems.