The IVa's, continuing to be built by Hughes Space, were an upgrade on the IV's, with different electronics and antenna arrays. presumably because of improvements in the electronics. The new platform remained the same size body, being just under 8ft (2.3m) diameter, but with the new extended antenna system now had a height overall ~23ft (7m).
Transponder count on this version had increased to 20, with 4 providing wide beam coverage for land mass areas.The remaining 16 transponders worked as small spot beams which could be directed to specific areas. The total capacity of this new version was 10,000 circuits.
This design incorporated beam separation by having more directional antennas which could point to east and west land masses. This meant that frequencies could be re-used for each route.
Six of this generation were launched, but 30 seconds into Flight 5, a fire started in the engine compartment which necessitated destroying the out of control rocket. The remaining five satellites performed well and exceeded their planned operational life.