AO-40 was heavily promoted in QST and downlinks were 10 dB stronger than AO-13 so activity went up.
Yep, sometimes I heard 4 or 5 stations in addition to the Colorado continuous SSTV downlink! And LEILA stepping on everything it could find (except the SSTV downlink :-(
I don't know how long it would have lasted. One interesting fact was that the AO-13 70 cm downlink worked much better in Los Angeles than the 2 meter downlink. Ambient noise was about 15 dB lower.
AO-40 had downlinks strong enough to actually use. AO-13 was definitely for weak-signal operation and needed serious antennas. Karl's analog HELAPS was realy pushing the envelope to get near 100 kHz bandwidth. An SDX could do it easier - but we really need to prove the SDX can tolerate the radiation and recover from a hit. A reliable narrowband transponder is to be preferred over an unreliable wideband transponder :-) The original Eagle proposal, if memory serves me correctly 9it often does not) was to have a linear transponder and the SDX was goign to be an experiment on the 2 meter downlink, 50kHz wide or so, with a bypass at the IF so if it became unreliable we could still get engineering beacon data on that downlink. A coded S-band downlink is probably even better, though, based on AO-40 experience.
73,
Lyle KK7P