From: <Chris.Phillips_at_email.protected>
Date: Mon, 1 May 2006 10:17:29 +1000 (EST)

Hi Guys,

We are now offering 256 Mbps, 512 Mbps (in two modes) and soon 1 Gbps as
standard recording modes with the LBADR systems.

Some of these modes require the use of a second DAS, so we need to update
the standard modes for each frequency to cover the range needed for the
second DAS.

The three new modes are:

  256 Mbp: 4x16 MHz. Standard "VSOP" mode but both polarisations
                recorded

  512 Mbps: A: 2x64 MHz recorded (one 64 MHz per IFP on the DAS)
                B: 8x16 MHz (Huygens mode). Basically VSOP mode but
                   using 2 DAS in parallel (usually recording onto a
                   single PC but not required or relevant here).

 1024 Mbps: 4x64 MHz. Basically the same 2x64 MHz mode above but
                   using 2 DAS in parallel (onto two recording PCs).

My suggestion is that for single DAS modes (ie 256 Mbps & 512 Mbps [A])
the centre DAS frequency should stay as it is.

For Dual DAS modes, DAS1 should be set to the same frequency as if it was
a single DAS mode. The second DAS should be centred so that the *recorded*
channels are contiguous in frequency. This means the centre frequency for
the second DAS will be different between 512 Mbps [B] and 1 Gbps mode.
Keeping the first DAS frequency fixed is really important as some
observatories only have a single DAS!

For example (I am not going to do this for every frequency...) for C band
the standard frequency ranges are
                          Range Centre
 Single pol ("vsop") 4808-4824 4816
 Dual Pol ("at16s") 4800-4832 4816

So the suggested new modes would be

 256 Mbps 4800-4832 4816
 512 Mbps [A] 4800-4848 4816 4848
 512 Mbps [B] 4784-4848 4816
 1 Gbps 4784-4912 4816 4880

The outstanding questions left are:

 - How to handle Tid, especially narrow 2 GHz frontend
 - Another RFI etc issues around current standard frequencies

Cheers
Chris
Received on 2006-05-01 10:17:51