The IRA Starter window is used to set parameters for the Gnu Radio receiver subsystem, then start the main IRA application.
This control is used to set the desired observing bandwidth (and thus, the underlying sampling rate) for the receiver subsystem.
The choices are:
250KHz
500KHz
1MHz
2MHz
3.2Mhz
4MHz
6.4MHz
8MHz
16MHz
You should pick a bandwidth that is compatible both with your observing regime, and the compute power available to you. For example, a dual-CPU Pentium D 925 system running at 3.2GHz can observe a single channel at 8MHz bandwidth, with only occasional buffer overruns from Gnu Radio.
A more modern, 4-core system running at 3.5GHz can easily handle a 16MHz input stream.
This control determines what mode the receiver subsystem is running in. The choices are:
single Single channel. The channel is determined using the Side control
dual Dual channel. Used for dual-polarization input
Note you MUST have two identical daughter-cards installed for this mode
interferometer A special dual-channel mode that is used to perform two-input interferometry
Note that you MUST have two identical daughter-cards installed for this mode. This mode also creates a “Show Interferogram” control on the main IRA window.
split A special dual-channel mode that is used to conduct dual-beam, single-polarization studies. This mode allows sky mapping at a higher rate, and also allows for so-called validated transient detection—any transient that is only detected in the primary beam is declared a transient while transients that appear in both beams are suppressed.
This control determines, for single-channel mode, which side of the USRP to use for input. The choices are:
A Side 'A'
B Side 'B'
This control determines the sample rate used for pulsar observing. Note that the total detected power is also determined from the pulsar input, as well as the transient detector. The choices are:
2KHz
4KHz
8Khz
10Khz
20Khz
25Khz
You should pick a sample rate that is as high as your CPU will handle, and it should also be an even divisor of the input bandwidth. The higher the pulsar sample rate, the lower the residual pulsar frequency/phase error in the pulsar display window.
This input area allows you to enter your local longitude, which is required in calculating your local mean sidereal time (LMST). Use decimal format, with negative values used to indicate longitudes that are WEST of the prime meridian. For example, -63.500 is 63 degrees, 30 minutes WEST longitude, while 63.50 is 63 degrees, 30 minutes EAST longitude. Remember to press ENTER to have the entered longitude take effect.
RxA Gain Correction/RxB Gain Correction
These controls can be used to adjust for gain imbalances when using dual mode, interferometer mode, or split mode. By default they are both set to 1.0.
RA MODE
This choice control sets the mode used to determine RA (Right Ascension) during an observation run with IRA. The choices are:
manual
RA is input manually in the RA input area of the IRA control panel
transit
The RA is set dynamically to the current LMST—which is useful for instruments set up in meridian transit mode, in which the azimuth axis is fixed on a line that runs exactly NORTH-SOUTH through the axis of the dish, and only the declination (elevation) axis is movable.
external
This mode allows IRA to get RA (Right Ascension) information from an external file. When this choice is selected, a file browser will pop-up, to allow you to select a file from which RA information is determined dynamically. While operating in this mode, IRA will inspect the selected file once per second to determine current RA information. This allows external tracking and telescope control software to control the antenna, while informing the receiver where the antenna is pointed.
DEC MODE
This choice control sets the mode used to determine DEC (Declination) during and observation run with IRA. The choices are:
manual
DEC is input manually in the DEC input area of the IRA control panel
external
This mode allows IRA to get DEC (Declination) information from an external file. When this choice is selected, a file browser will pop-up, to allow you to select a file from which DEC information is determined dynamically. While operating in this mode, IRA will inspect the selected file once per second to determine current DEC information. This allows external tracking and telescope control software to control the antenna, while informing the receiver where the antenna is pointed.
This input area is used to enter your license key. If you don't have a license key, the software will automatically expire approximately 30 days after you receive it. If you don't have a license key, enter the word “none” in this area. Remember to press ENTER to have the entered license key data take effect.
START RA RECEIVER
This button control causes the IRA main control panel to start, and this starter panel to be closed. The IRA control panel will use the parameters provided in the startup panel.
EXIT
This button control allows you to exit the IRA starter, without causing the IRA main control panel to start. This is useful for changing stored settings, without starting the IRA main control panel.
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