Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Absolute calibration of a wideband antenna and spectrometer for sky
  noise spectral index measurements   A new method of absolute calibration of sky noise temperature using a
three-position switched spectrometer, measurements of antenna and low noise
amplifier impedance with a vector network analyzer, and ancillary measurements
of the amplifier noise waves is described. The details of the method and its
application to accurate wideband measurements of the spectral index of the sky
noise are described and compared with other methods.

17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
12
The categories of this paper are: nucl-th
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
4
The categories of this paper are: cond-mat