lbw  check the rf filterbank

22apr13: check lbw filterbank.
11mar06: check filterbank

22apr13: check lbw filter bank.

    a2749 (Barbara)  reported instabilities in polB of lbw during apr13 runs. They were using the 1230-1470 filter with the 1370 hipass filter.
    On 10apr13 we did a cable test on the 1370 hipass cable going into,out of the filter bank. We saw no jumps in the signal. A loose feed through connector was found at the output of the filter bank (it was tightened). A2749 problems continued after this.
    On 22apr13 a test was done to see if the rf switches in the filter bank were making lousy contact.
The test consisted of:

The data processing was:
The plots show the calDeflections from the test (.ps) (.pdf):


processing: x101/130422/,

11mar06: check lbw filterbank

        A diagnostic was written to test the lband filterbank.

The data taking consists of:

processing the data:

    Use the following definitions:     For each filter we have N sets of  10 measurements of calon,caloff (with 2 seconds between each measurement. We compute:       The calDeflection will  show changes caused by Gif or Gfilt. It will not be sensitive to changes in Ttm (at least those that change slower than 2 seconds).

    The calRatio will show variations in Tsys caused by Ttm. Ttm can change if the filter relays do not close properly and increase Tsys. It will also change when sources drift through the beam increasing Tsys. When sources drift through, it should occur in both PolA and polB (since most sources are not highly polarized). The calratio will not be sensitive to changes in the gains.

The data