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Last Update: 8th May 2019

Receiver Tuning

The receiver should be tuned to the frequency you observe. In general, you need to tune the receiver once at the beginning of your observations (If you observe different frequency setup with the same receiver on the same day, you tune the receiver at every changing the frequency setup). Since tuning methods differ one by one, this page shows how to tune each receiver. Before moving to following procedures, you should change the direction of mirrors in order to the receiver you use can receive the signal from the sky. If you will observe continuum, special set-up is needed. Please print your device tables and pass it to the assistant.

T70 receiver

T70 receiver will be tuned with a program that can be remotely accessed with the Tuning Machine (its monitor marked 7 in the figure below).

monitors

The tuning machine tunes the receiver via the machine located in the Nobeyama 45-m telescope. Usually, a remote connection is already established. If the connection is lost, push the "start" button and choose "remote desktop". Account-ID and password are memorised. If not, please ask the assistant.

T70 receiver is adjusted based on the premise that a tuning procedure is performed at EL=70 degrees. Pushing "TUNING" button at the antenna console enables the telescope set EL=70 degrees. Please do not forget to set the observation mode (push "ALL PROG" and "SLAVE" buttons on the antenna console) when you start observations.

To make the tuning programs an operation mode, you should push the "arrow" button on the top-left in the program.

Tuning GUI for T70

Since T70 receiver is a 2SB receiver, you can measure a sideband ratio (or, an image rejection ratio: IRR) when you tune the receiver. The measurements of the IRR enables you to calibrate the daily variation of the system. It allows you to convert the data into main beam temperature (TMB) on the data reduction. It would be better off obtaining the IRR in case that your target lines seem to be weak (TA*< a few K) even for the standard source.

Here, we introduce the tuning procedure for T70 receiver.

  1. Launch the Tuning Program

    The tuning program is named as T70tune**.vi. This program is usually already launched. You can launch the program by double-clicking the desktop shortcuts if it is not. In the case of stopping the program, please click "STOP" button at bottom-left in the program.

  2. Run the Tuning Program

    The tuning program will start running when the "arrow" button on top-left in the program is pushed.

  3. Tuning
  4. Measurements of the IRR
  5. Switch to the Observing mode

    Press "Tuning" at the tab bar. Then push the "Observation mode". You can now observe with T70 receiver.

Do not forget to copy the text file which contains the measured IRR. Please make sure your USB memory has no computer virus previously. Your text files are found in the directory named "T70IRRdata" at the local desktop (not at the remote desktop).

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H22, H40, Z45 receivers

It is no need to tune H22, H40, and Z45 receivers. After changing the direction of mirrors, you can start an observation by choosing the observing script at COSMOS GUI and pressing "START OBSERVATION" button.

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FOREST

Monitors for the FOREST receiver are placed behind the weather monitor and the Tuning Monitor for T70 receiver (marked 6 in the figure below).

monitors

FOREST monitor (Top) FOREST monitor (Bottom)

Left: A top side of the FOREST monitor. A remote desktop on the left is for a server connection (observers do not need to use), the right one is a web camera to monitor the FOREST.
Right: A bottom side of the FOREST monitor. On the left, it shows FOREST status monitor, while the terminal for tuning is in the right part of the monitor.

The FOREST receiver can be tuned with the terminal shown in the right part of the FOREST monitor (see the figure below). Since a tuning procedure for the FOREST is followed by the steps described below, it is convenient for you to use the command-line history (pressing the up and down keys at the terminal).

Terminal for FOREST
  1. Initialise the FOREST

    Enter the following command to initialise the FOREST receiver.
    > forest_initialize.py

  2. Receiver tuning

    You can tune the FOREST applying the best parameters which the observatory previously measured. The tuning command is as follows:

    > forest_SIS_tune.py tuning/loXXG-UL_step3_yyyymmdda.cnf

    where XX is the LO frequency, UL is a sideband which you intend to observe (Upper Sideband[USB], Lower Sideband[LSB] or USB/LSB), and yyyymmdda is the date when the observatory measured the parameters. Please select LO frequency as the frequency nearest to you specified in the device table. (The observatory send the PI a filename which suits for your observations. Please use it unless there is any problem.)

    For example, in the 2017-2018 observing season, the observatory prepares following tuning parameter sets (The names of parameter file may be changed during the observing season).

    LO Frequency [GHz] Sideband Name of a Parameter File
    86-88 USB/LSB lo86G_UL_step3_20161130i.cnf
    89-93 USB/LSB lo92G_UL_step3_20161104a.cnf
    93-96 USB/LSB lo94G_UL_step3_20171121d.cnf
    97-100 USB/LSB lo95G_UL_step3_20170329e.cnf
    100-102 USB/LSB lo101G_UL_step3_20161122w.cnf
    102-104.5 USB/LSB lo104G_UL_step3_20161122e.cnf
    105 USB-H/USB-L lo105G_U_step3_20170224a.cnf
    107-110 USB-L lo109G_UL_step3_20161129k.cnf
  3. Measurements of the system noise temperature and the sideband separation ratio

    To check the performance of the FOREST, you should measure the system noise temperature (Tsys) and the sideband separation ratio (or Image Rejection Ratio: IRR) along different IF frequency. First of all, push the "Tuning" button on the antenna console to set EL = 70 deg. Measurements will be performed with following commands:

    > exp_irr_with_IF_freq_sweep.py --lo_freq 105 --start 4 --stop 12 --step 1

    where "lo_freq" is the 1st LO frequency [GHz], which you specified in the frequency seeting file (DeviceSetting_***_xlsx) that you submitted with your proposal, "start" and "stop" are the IF frequency [GHz] where the measurements start and end, respectively. Regarding the "lo_freq", the first decimal place may be enough because of the flatness of receiver performance. "step" is the frequency interval [GHz] of Tsys and IRR measurements between "start" and "stop". In the example above, the measurements are under the setup of the LO frequency of 105 GHz, IF range of 4-12 GHz with a step of 1 GHz. These values should vary the observing frequency and numbers of target lines. The required time differs the data number to measure: typically saying it takes a minute to obtain the data for the setup of IF = 4-12 GHz with 1 GHz step.

    When the measurements end, the results will be shown on the terminal with values and the FOREST status monitor (bottom right area) with plots. If you click the plots on the FOREST status monitor, you can see the zoomed-up one (see the figure below). You can obtain the data by clicking a string under the plot (~.zip).

    an example of IRR measurement

    An example of Tsys and IRR measurements. Tsys in blue (the left axis) and IRR in black (the right axis). The relations between the beams, the polarisations, and the sidebands in the figure are as follows:

    FOREST Beam, Polarisation Relationship on IRR Measurement Figure
  4. Start observations

    The FOREST is now ready for observations. For a safety observation, we recommend you to run the following command to fix the tuning parameters unless you explicitly unlock.
    > forest_start_observation.py

  5. End observations

    When your observation ends, please run the following command to make the FOREST tuning machine a standby state.
    > forest_end_observation.py

    In the end, set the FOREST itself a standby state.
    > forest_finalize.py

How to address the trouble that the terminal does not respond ordinary during tuning of FOREST receiver

Due to troubles (including misoperations), the terminal may not respond, or the tuning process may suddenly stop. In principle, we hope that you report the situation to the assistant and ask for help. But you may resolve a problem with the following process (please report the situation even if you could solve the problem by yourself).

  1. (In case that the terminal does not respond and the Tuning Machine seems not to execute a command)
    Press Cntl key and C key at the same time to force-quit the command.
  2. Enter the following command to set flags as a normal end:
    > rforest_end_operation.py
  3. If you faced the problem before starting observations, the observatory recommends to tune the FOREST receiver again (i.e., start from the initialisation).
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