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M3 Tap Attenuator Kit Tips
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Setting The Frequency Compensation
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After constructing your Tap Attenuator Kit, you will have to adjust the frequency compensation for higher frequencies. The adjustment of the Tap Attenuator is quite simple and only requires a non-metallic tuning tool to adjust the two trimmer capacitors, a signal source with between +5dBm and -20dBm output, and your power meter.
- To begin the compensation adjustment, first program the highest frequency that you will be using, (i.e. 450 MHz) in to a frequency memory slot of the FPM-1. This is performed in the Frequency Counter mode, CH1.
- Once the frequency has been programmed into memory, switch from CH1 to POWER on your FPM-1. Connect your signal source (signal generator, antenna analyzer) to the Power Meter input of the FPM-1. Set your signal source to the frequency you have programmed in to memory. The ouput level of your signal source should be between +5dBm and -20dBm. The power meter will display the output level from your signal source.
- Press the ZERO key on the FPM-1 and 0.0dBm should be displayed on your FPM-1. You are now in Relative Mode and all measurements will be displayed with the signal level of your source as the 0.0dBm reference.
- Disconnect the signal source from the FPM-1 and connect the BNC connector marked 'TO POWER METER' on the Tap Attenuator to the FPM-1 Power Meter using the male-to-male BNC connector provided in your kit.
- Connect the provided BNC T-connector to the BNC connector on the Tap Attenuator marked 'INPUT'.
- Connect your signal source to one side of the BNC T-connector and connect the other side of the T-connector to a 50-ohm dummy load.
- Adjust the trimmer capacitor that is farthest away from the BNC connector for a maximum reading on the FPM-1 display but do not exceed -40dBm. Adjust the trimmer capacitor closest to the BNC connector for -40dBm.
- There will be some interaction between the lid of the enclosure and the compensation adjustments. Set the lid of the enclosure in place and note the attenuation value displayed on the FPM-1. Remove the lid and readjust the trimmer closest to the BNC connector to offset the change in attenuation level. Repeat this step until the power meter displays -40dBm with the lid in place.
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For further instructions on using the Tap Attenuator with the FPM-1, refer to the User's Manual provided with the kit.
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