If you absolutely have to have a 50% duty cycle, then you can do it in hardware by adding a toggling latch to the output and setting the 'steps per second' to be double what you require.
The output of the toggling latch has a "divide by two" action whose output goes high on the first short pulse and low on the second. This will give a 50% duty cycle, but at half the original frequency.
To make a toggling latch, take a 74LS74 and connect the /Q back to the D input. Feed the short pulses into the clock. Have a search on the web and you're bound to find something.
Sounds a bit technical, but it will be a one-chip solution since a 74LS74 has two such latches, each with a Q and /Q output.
Mike Evans
TRW Conekt
N.I. Alliance Member, UK
http://www.Conekt.net