GSSI SIR 30, Manual

Page: 84 / 150

Geophysical Survey Systems, Inc. SIR® 30
Manual
MN 93-101 Rev E 78
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GPS:
Select CUSTOM if a GPS system is to be used during the survey. The User must enter the
location of the GPS receiver x and y offsets with respect to the antenna connected to Channel 1. If the
GPS antenna is mounted to the GPR antenna, both the X and Y values will be zero (0).
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Antenna Entries Antenna 1 - 2:
The User should enter the details of the antennas connected to the
Channel 1 and Channel 2 inputs on the SIR 30. The User should select the default setup values for
both of the antennas
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TX- RC Mode:
The User should then set the antenna transmit and receive mode of both Channel 1 and
Channel 2 to bistatic. The User will note that in this setup, (see Figure 113 above) we have connected a
Model 50400 and a Model 50400S antenna. While both of these antennas have a 400 MHz center
frequency, one antenna is capable of operating at a higher transmit rate, the 504000S.
As indicated the Note in Chapter 2 (above pp 10), in cases where the maximum transmit rate of the
antennas connected to the SIR 30 is different, the SIR 30 will use the highest common transmit rate
across all channels i.e. the transmit rate for ALL channels will be equal to the transmit rate of the
slowest channel. The Systems Settings menu will display both antenna transmit rates. The transmit rate
used during data collection will be written into the File Info and stored in the file header.
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As there is no direct coupling signal between the two (2) antennas, the User must place the antennas
side by side in order to determine the position of the direct signal (the ‘air wave’) transmitted from
Channel 1 to the receiver (Channel 2). The User should place the transmitting antenna (Channel 1)
next to the receiving antenna (Channel 2) as illustrated
Error! Reference source not found. below.
Figure 116: Bi-Static antenna setup. Channel 1 (Transmitter) on right, Channel 2 (Receiver) on left.
Control cables omitted for clarity.
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In order to minimize the travel time of the direct wave from the transmitter to the receiver, the
antenna(s) should be positioned such that the transmitter dipole (TX) of the Channel 1 antenna is
closest to the dipole of the receiver (RX) of Channel 2. The dipole polarity axis of all current GSSI
shielded antenna models; 62000, 52600, 5100B, 5101, 3101A, 5103, 50400S, 5104A, 5106A is the
same. The Transmitter dipole (TX) is located under the handle brackets of the antenna. The User
should position the antennas next to each other in the manner show in Figure 114 (above) so that the
transmitter of Channel 1 (on the right in Figure 114) is closest to the receiver on Channel 2(on the left
in Figure 114 above). Once the User has positioned the antennas, ACCEPT the System Settings.
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The User must then set the Run Mode to TIME for the initial position adjustments. Bistatic data may
be collected in the Distance mode for variable fixed offset profiles or in the Point mode if the User is
wishes to collect Common Mid Point (CMP), Wide Angle Refraction Reflection (WARR) or
transillumination data.