TPSPEEDH is an obsolete parameter because tape is no longer used.
TPSPEEDH tells SCHED the recording speed of the tape in inches per second when recording at high density. The low density record speed is specified with TPSPEEDL. SCHED uses this information to calculate where on the tape each scan is located, when to reverse direction, switch head assignments etc. The density at which the recording should be made is set by the DENSITY parameter in the tape initialization inputs.
TPSPEEDH and TPSPEEDL will default to the correct values for tapes written on VLBA, Mark III, Mark IV, VLBA4 and S2 systems. It should not be necessary to specify them and it is probably safer not to do so.
The speeds currently in use are:
The VLBA and VLA started using high density on all thin tapes on about 1 May 1996.
Note that the recording speed determines the speed up factor on playback. All playback on the VLBA correlator is done at the higher speed (160, 266.66 or 270 ips). Projects recorded at less than the highest speed will play back in less than real time. It is important that a reasonable fraction of projects have a speed up factor of more than unity or the correlator will not be able to keep up with observing.
The VLBA control file only specifies STOP, +RUN, -RUN, +REWIND, or -REWIND, and the on-line system deduces the speed to use from the format and samplerate. If SCHED has the values different from what the on-line system chooses to use, the direction and head position commands, along with tape changes, will be wrong and the project will be messed up.