To enable the 5 Hz, use OSP MID 136.  The field “Position Calc Mode” can be interpreted this way:

Bit Mapped.  When set to 1, a bit enables the function.

Bit         Function

—-         ———–

0                     Almanac Based Positioning

1                     Reverse EE

2                     5 Hz Navigation

3                     SBAS Ranging

4                     Fast time Sync

So set bit 2 to a 1 to enable 5 Hz navigation.

reference OSP document

Posted in: GPS, Sirf IV