Calibration DDF unit will be necessary at the first time or any time you use your DDF2020 on a different vehicle.
It is necessary to recalibrate, if you remove and replace the antennas on your vehicle, and they are not placed back in precisely the same locations and geometry making.
Installing the antenna unit on the roof of your vehicle
- Place N on the frontward of car (0 degree)
- Place S to on the backward of car (180 degree)
- Place E to on the passenger side of car (90 degree)
- Place W to on the driver side of car (270 degree)
- Connect the RF output from the Antenna Control unit to the VHF FM receiver’s antenna connector
- Connect the Antenna Control cable between the Antenna Control unit and DDF2020’s Main unit.
- Connect the FM receiver's external speaker audio to the audio input jack on DDF2020 main unit.
- Turn on the power to your DDF unit.
- Turn on the receiver and open the squelch on your receiver, then tune it to the frequency desired.
- You should hear a 430 Hz tone imposed on any audio present depending on the Antenna Speed selection at startup.
The easiest way to calibrate is to drive your vehiecle to an open area and have a friend position himself/herself at least 100 ~150 feet (30 ~40 m) away with low power and directly ahead of the vehicle while transmitting an unmodulated carrier.
If your friend is using an HT, ask him/her hold it vertical at approximately the height of the vehicle antennas. If the DDF already turned on, check which direction the direction LED shows and adjust the potential meter through Calibration Hole with a small screw driver. The 0 degree LED should indicate that the signal is directly ahead of the vehicle (N on antenna control unit).
As a double check, your friend can transmit while circling the vehicle at approximately the same distance and the display should follow him/her. The DDF will retain this calibration even after power is turned off.
An alternate method of calibrating the unit is to drive directly towards a known transmitter site, across an open area. This will give you the best calibration but may be difficult or impossible in urban areas. The simpler method should be quite adequate.
You may develop other methodologies that work better in your situation and by all means use them