following paragraphs from an Australian VLBI memo, http://www.atnf.csiro.au/vlbi/documentation/sched/node161.html
the type of Data Acquisition Rack present. This is mainly to identify the
type of formatter, which will let the program know about the capabilities
available. Valid types are: VLBA, MKIV,
VLBA4, MKIII, S2, K4, VSOP
and NONE. The main non-obvious option above is VLBA4, which is a
VLBA DAR but with a Mark IV formatter installed. This will have VLBA BBC's
and IF switching, but Mark IV formatting characteristics.
the type of tape recorder(s) present Valid options are: VLBA, MKIV, VLBA4,
MKIII, S2, K4, VSOP and NONE. The VLBA4 option is for VLBA recorders
which have been modified for 16 Mbps per track operation. They are usually
associated with MKIV or VLBA4
are several VLBI Data Acquisition (DAS's) and recorder systems currently
in use. In the Mk3 family there are the Mk3a, Mk4, VLBA geodetic VLBA (VLBAg)
and VLBA4. In the K4 family there are the K4-type1, k4-type2 and
k4-VSOP. The S2 family......
At the maximum data rate, each of the 64 data streams from the formatter transfers 16Mbps of data. With parity information added, the maximum bit rate to each head is 18Mbps. This requires that the tape speed be 18E6 bps/56.25E3 bits per inch = 320 inches/sec.
Data is written on the tape with a maximum longitudinal density of 56.25 kb/inch. The maximum number of bits stored on an 18,000ft reel of tape is therefore 448 tracks x 56.25E3 bits/track/inch x 18000 ft x 12 inches/ft = 5.44e12 bits = 5,443 Gb or 680 GBytes.
Our Mark 4 formatter has 32 analog input ports, enough for USB and LSB from 16 BBCs. The system uses 16 of these inputs for the USB and LSB signals from our 8 BBCs. When and if the additional 6 BBCs are installed, we will use another 12 inputs for a total of 28 out of 32. The formatter contains a 2-bit digitizer for each one of its 32 analog input ports. There are 64 output lines to the two head stacks.
formatter, the 64 output streams from the digitizers are not simply hardwired
to 64 heads. At low data rates, data from more than one source can be written
on a track. At high data rates, data from one source can be spread across
MEMO #230.2, "Mark IIIA/IV/VLBA Tape Formats, Recording Modes and Compatibiliity")
1. Signatron Tape Drive Documentation: one volume, a 3" thick three-ring binder with no title page or table of contents. This volume contains copies of Haystack circuit diagrams, mechanical drawings, parts lists, and timing diagrams, but no text. The first section is "Dry Air Kit"
2. Signatron Data Acquisition Rack (DAR) Documentation: a 4" thick three-ring binder, again with no title page or table of contents, or text. This volume contains copies of Haystack schematics for the formatter, decoder, BBCs, etc. At the end is a Signatron-generated wiring list for the rack.
3. Metrum Technical Manual - "Maintenance Instructions", Volume 1 of 2 and Volume 2 of 2, each in a metal back binder, 3" thick.
Tehnical Manual "Operators Instructions for Model 96(C), Black plastic
spine, 1" thick.
5. Metrum Recorder Documentation V1.2.4 CD ROM Disk compiled by Michael Wunderlich of Bonn. Contains Haystack schematics and memos, text from Interferometrics manuals, etc. Very useful.
Technical Report No. 14, Rev. B Operation of the VLBA Tape recorder at
the VLA and the VLBA Sites, C. Janes and G. Peck, Nov 1993.