RECEIVER SETUP
Section 6, Page 17 May 2002
SYNCHRONIZING THE TRANSMITTER AND RECEIVER
The GDP-32
II
receiver and XMT-32 Transmitter Controller have identical crystal oscillators and
circuitry for dividing the crystal frequency into a set of precise, selectable, operational
frequencies. For synchronous operation, the two oscillators must be equal in frequency to
provide an absolute phase reference.
NOTE: For surveys such as complex resistivity (CR), roll-along IP, and NanoTEM where the
receiver is linked to the transmitter directly, synchronization is not required. The receiver clock
controls both the transmitter and the receiver.
At least one hour prior to adjusting the frequency:
1. Press the Power On/Off Button on left side panel of the GDP-32
II
to apply power to the
crystal oscillator. Make sure that the red LED marked CRYSTAL ON is illuminated.
2. Turn the XMT-32 Power Switch to ON.
NOTE: During continuous field operations, power to either the GDP-32
II
or the XMT-32
crystals should rarely be turned off. Crystals can remain on during charging. This practice
eliminates the wait for the crystal ovens to warm.
NOTE: Before using the “Synchronize to XMT” routine or the manual synchronization routine,
make sure you have a good calibration for the RPIP exists (FDCALS in the CALIBRATION
cache) as that program is used in the synchronization routine.
After the crystal ovens have heated for at least 60 minutes:
1. Disconnect the Battery Charger.
2. Connect the synchronization cable between the I/O port on the XMT-32 Transmitter
Controller and the TRANSMITTER I/O port on the Control I/O panel of the GDP-32
II
receiver (Figure 6.3.)
3. Switch the PHASE/BATT switch to the BATT position to check the transmitter
controller battery voltage. The voltage should read at least 12.5 volts. If lower, there is
either a poorly charged battery or a problem with the power system (see Section 15 -
Maintenance.)
4. Switch the PHASE/BATT switch to the PHASE position. Observe the needle on the
PHASE/BATT analog meter. Any needle movement indicates that some frequency
difference exists between the GDP-32
II
and the XMT-32 oscillators.
The faster the needle is swinging, the greater the frequency difference. If there is
absolutely no swinging over a period of a minute, the oscillators are either adjusted to the
exact same frequency (skip to step 10), or the oscillators are very different in frequency
and the resultant beat frequency is beyond the response of the meter (see Section 6 to
manually trim the XMT-32).
Frequency adjustment and synchronization are accomplished with the GDP-32
II
by
executing the “Synchronize to XMT” function (Utilities Menu - Option 4.)
5. Follow the directions given on the screen:
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