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Operation confirmation of Transmitter

Operation confirmation of the transmitter It turns on the power of the transmitter without mounting PIC. Because the base of the oscillation transistor isn't controlled by PIC when not mounting PIC, it oscillates continuously. It connects a frequency counter with the collector of output transistor (TR2) and it adjusts an oscillation frequency. A frequency is adjusted by the pitch of the oscillation coil. I adjusted to the frequency (about 83 MHz) which doesn't overlap with the FM broadcasting. There is no problem at the other frequency. Measurement of the frequency change The frequency stability of the oscillator which was used this time isn't good. I measured a frequency change from turning on the power. The measurement of the frequency was done for 7 minutes and the frequency changed from 82.985 MHz to 83.180 MHz. The band is 195 kHz. This measuring time was too long. Actually, the frequency change immediately after the turning on is important. The receiver should be controlled by the transmitter. The operation of the transmitter may be short time. Generally, the receiver can be controlled below 10 seconds. The frequency change in 10 seconds was to 4 kHz be. This frequency change seems to be cause for the change of the capacitance of the transistor by the heat which is caused by the electric current of the transistor. This frequency change is related with the receiving sensitivity with receiver. In case of being the receiver which can not do receiving in the 4-kHz frequency change, it is a problem. Generally, even if it shifts by 4 kHz, there is no problem. However, when the electric wave is weak, the influence sometimes comes out. Measurement of the frequency change by the power supply voltage The power of the transmitter is a dry battery. So, the dry battery consumes when using long and the power supply voltage falls. I changed a power supply voltage and measured a frequency change. The oscillation frequency changes when making do the operation of the transmitter. Therefore, I measured a frequency after stopping a transmitter after setting voltage and keeping time for a while. The frequency change when changing power supply voltage from 7V to 11V was to 16kHz be. This is not a big change. It seems that it does the operation even if the dry battery weakens. Confirmation of the oscillation frequency by the dip meter I recognize the oscillation frequency of the transmitter by the frequency counter. Moreover, I checked a frequency with dip meter. I will use a dip meter for the frequency adjustment for the receiver. So, this measurement is the operation confirmation of the dip meter.