This project will explain the function of a simple RF field meter. The unit will be in great help to tune transmitters for best performances.
This unit will not show you the exact power like a power meter, but it will show you the relative power transmitted out from your transmitter and antenna. The panel meter is connected to the PCB with 5 meter long wire. In this way you can put the field-meter 5m away from where you are and still be able to watch the panel meter.
The author will tell you how he uses the filed meter. Place the RF field meter 5 meter away from your transmitter. Then put all variable capacitor to middle. Switch on the transmitter and go to your RF filed meter. Then set the gain (with potentiometer) so that you will get half of max reading on the panel meter. Then switch off the transmitter and set the offset (with other potentiometer) so I get zero reading on the panel meter. Repeat this tuning process until looks good.
Now you can start tuning the transmitter and watch the panel meter. All you need to do is to tune for max reading on the panel meter. Then you know the RF field is at max strength. He also advices you to receive the signal you are transmitting to check that it sounds good. Also check the current to the transmitter so it don’t get to high.
Usually the current go down when good tuning has been done and you got max power.
Another good thing to monitor is the temperature of the transistors.
Don’t let them go to hot.
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