Last Update: 22th November 2017

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Current SAM45 Status (as of 20th November 2017)

The arrays painted in red are currently not available. Green indicates available arrays.

Due to the mechanical reason, when one array of A(2n-1), A(2n), A(2n+15), and A(2n+17) (n: 1~8) is out of order, rest 3 arrays cannot be used either. Spectral Window (SpW) mode is only available for FOREST receiver. If SpW mode is on, users can use SpW2 (array 17~32).

SpW1 SpW2
A1 A17
A2 A18
A3 A19
A4 A20
A5 A21
A6 A22
A7 A23
A8 A24
A9 A25
A10 A26
A11 A27
A12 A28
A13 A29
A14 A30
A15 A31
A16 A32
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Device Tab



The device tab is desined to make the device table, in which frequency setup is written.
NOTE: We provide sample device files. Please select one of sample files from "Samples" button first. Then, modify "Track freq.(GHz)", "IF freq.(GHz)", "Att." in Frontend Tab, "Rest Freq. (GHz)" and "Resolution (kHz)" in Backend Tab according to your observing configurations.

Device Table [mandatory field]

Enter a name of the device table. A configuration file will be saved under your working directory with the name of

	<the name of the Device Table you defined>.ndevice

The limitations of a filename of the device table are as folllows:

NOTE: You can save the input parameters anytime you want (the nobs allows you to save the scan table even if some mandatory fields still blank). The nobs does not check whether these input parameters follow the rules at that time.

Click the Check button for a basic check of the parameters. The nobs calculates and compares the relations of the Track Freq., IF freq., Rest Freq.. If an input value violates the setup rules, the nobs notifies the error in the information box at the bottom-right corner. The detailed frequency set-up is shown in the summary tab.


Name Explanation
Array Array ID (A01~A32)
FE Frontend: the receiver and the polarization
IF selected IF
Start Freq. (GHz) Rest Freq. - Bandwidth/2
End Freq. (GHz) Rest Freq. + Bandwidth/2
Resolution (kHz) Frequency resolution selected in each sub-array
Bandwidth (MHz) Corresponding Bandwidth (relationship between the frequency resolution
and the bandwidth is summarised in Resolution section)
LO(DC) Freq. (GHz) Down-converted local oscillator frequency.
Although in most cases there is no need to take care of LO(DC) frequency, user may consider LO(DC) frequency.
In such case, a derivation of LO(DC) frequency may helps to make the device table.
A calculation method is described in Appendix

Naming Rules of Sample Files

The observatory provides large numbers of sample files according to the following naming rules:

Screenshots of each sample file and their concrete meanings are shown on the following page.
List of Sample Files of Device Table

Device Table for Pointing Observation

When you make an observation script for pointing observations, the observatory recommends using the sample device file named 'h4_u_4.ndevice'. This sample table uses H40 receiver and 4 arrays of SAM45, which is designed to observe SiO(1-0) maser. (If you do not have a specific reason, it is enough to use just 4 arrays of SAM45 for achieving the purpose of checking and correcting the pointing accuracy of the antenna.)

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Note (optional)

You can use this space to leave any memo for the device table. A character limit is 100, and a line break is prohibited.

Frontend Tab

In the frontend tab, users choose a receiver and set its target frequency range.

Frontend

IF-Backend

The role of the "Att"enuator:

A value specified at the attenuator (Att) is added to the initial value of the attenuator in the IF system, only when the receiver sees a hot-load during the absolute intensity calibration. This additional attenuation reduces the power of a signal to stay in the good linearity range of the system. An inappropriate value specified at the attenuator may cause incorrect values of Tsys and intensities of spectral lines.

Parameter Config File [Not in Use]

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Backend Tab


With the backend tab, users can arrange the frequency setup for a spectrometer. There is only one spectrometer, SAM45, is mounted on the Nobeyama 45-m telescope. The SAM45 spectrometer is a highly flexible FX-type correlator (spectrometer) that allows a maximum of 32 GHz of bandwidth (2GHz, ~1.6GHz effective, x 16 arrays) in 4096 spectral channels. The arrays are donated A1, A2, ..., A32 in the device table. SAM45 consists of 32 arrays, where the resolution of the arrays can be set at 3.81, 7.63, 15.26, 30.52, 61.04, 122.07, 244.14, 488.28 kHz. The prior 16 arrays are called Sub-array 1, while the posterior 16 arrays are Sub-array 2. The sub-array 2 cannot be used unless the Spectral Window (SpW) mode is selected. If users set the 'sub-array' mode on, two independent frequency-resolution setting can be applied for the sub-array 1 and the sub-array 2.

The bandwidth for each resolution setting can be calculated by multiplying the number of channels (4096) for each array (see table). All reciever (FOREST, T70, Z45, H40, and H22) can be connected to SAM45.

sub-Array1, sub-Array2 [fixed field]

This field allows users to know the connection of the signal from the receiver to an array in SAM45. IF(n) is connected to SAM45 array A(n) and A(n+16) (n:1~16). For example, if FE of 'IF01' is filled with 'FE01', you are connecting the receiver you chose for FE01 at Frontend Tab and the signal will be sent to SAM45 A01 and A17.

sub array mode

Sub-array mode allows you to set a maximum of two independent frequency-resolution (bandwidth) modes. Simply enable/disable the sub-array by clicking on the radio button. When enabled, you can choose the second set of the frequency resolution. The sub-array mode is available with FOREST, T70, H40, and H22 receivers using at least 16 arrays.

SpW mode

The spectral window (SpW) mode is only available for FOREST receiver and users should use dedicated sample files (a filename with fs_~_s.ndevice). When SpW mode is enebled, users can set two different spectral-resolutions with the same IF and sideband (i.e., USB-H, USB-L, LSB-H, and LSB-L). Note that the specified IF range and the LO frequency cannot be changed. Also see the status report about Spectral Window mode.

Sub-Array1 Spectral Window1, Sub-Array2 Spectral Window1, Sub-Array1 Spectral Window2, and Sub-Array2 Spectral Window2

Examples

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Appendix: Derivation of LO(DC) Freqency

The LO(DC) is used to down-convert again the user-specified IF frequency into a lower frequency. In most cases, users do not need to take care of the LO(DC) frequency because it is automatically checked whether it is within a valid range. However, sometimes it may need to adjust the LO(DC) frequency by users.
LO(DC) frequency can be derived as follows:

Step 1: Calculate the following value, which is useful for the derivation of the LO(DC) frequency, FLO(DC).

FdiffIF = Frest - Ftrack +/- FIF,

where Frest, Ftrack, and FIF are the rest frequency, the tracking frequency, and the IF frequency, respectively. +/- signs correspond the sideband (+ for USB and - for LSB).

Step 2: Derive the LO(DC) frequency. Choose an appropriate equation based on the receiver and the sideband which the user intend to use.

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