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At a minimum, a 100 W HF radio and good 50ohm dummy load can be used to calibrate the HF sensor and display unit. Even if you know how much power your radio emits, consider using an additional wattmeter of known accuracy to assist you during the calibration process.
Start by setting R1 through R8 to their center positions. Connect the HF sensor to INPUT 1 on the main board. Attach a voltmeter between ground and the reverse test point of the HF sensor. Apply 100 W through the HF sensor to a dummy load or resonant antenna; adjust C1 in the HF sensor for minimum voltage. The minimum reading should be just about 0 Volts. A reading of 0.1 Volt or less is fine. Be sure the pot for the reverse channel is centered for this adjustment. It is possible to get a 0 Volt reading if the pot is not set correctly.
Again apply 100 W and adjust R1 on the main board so that the forward display reads 100 W. Set the LCD to display numbers instead of the bargraph. Swap the input and output leads of the HF sensor and again apply 100 W. Adjust R2 to read 100 W on the reverse display. An error message (REV>FWD) will appear, but the display is still visible between
For VHF and UHF, connect a VHF/UHF sensor to one of the other channels. Apply RF power and adjust the corresponding variable resistor to obtain a correct forward power display. Swap the input and output leads and repeat for the procedure for reverse power. Repeat the foregoing process for the other channels by connecting the appropriate sensor to each input and adjusting the corresponding variable resistors.
Remote Operation: The display head is designed to mount at the station transmitter. The display unit can be used as table top or under shelf by using the mounting bracket. The mounting bracket can also be used in a mobile installation.
The remote sensor is supplied with a
For remote sensing at long distances, a three wire shielded cable must be used. The wire must be #20 or larger to prevent voltage loss with distances over 100 feet.
The resolution of the
Even though the overall accuracy as compared to a Bird wattmeter is better than 0.1%, the actual accuracy still depends on the calibration.
Trouble Shooting: If there are any problems, first check all components for proper value, placement and polarity. Next look at the solder connections. Check for cold solder joints and solder bridges first, since they are the number one cause of problems with the kits.
Does nothing: Check for 12 volts getting to PC board (be sure the switch is on). Check for 5.0 volts out of 7805 (the left pin). Make sure the