Operation confirmation of Receiver-1

Adjustment of the receiving frequency

I used Dip meter, High frequency detector and Circuit tester for the adjustment of the receiver.
In case of the high frequency circuit, the resonant frequency is not as the calculation. The wiring becomes the part of the coi and the capacitance changes in the interval of the wiring and influences the value of the capacitor. So, an adjustment is always needed.

Adjustment of the high frequency transformer

There is a notch at the top of the core of the high frequency transformer and the position of the core can be adjusted with the screwdriver and so on. When turning a core to the right, a core is inserted in the coil of the transformer. With this, the inductance of the coil becomes big and the resonant frequency becomes low. When turning a core to the left, the core gets away from the coil. With this, the inductance of the coil becomes small and the tuning frequency becomes high. As for the position at the head of the core, the position of the surface of the transformer is desirable. It changes the value of the capacitor to be putting in the coil in parallel to become like this as possible.

Adjustment of L1

It connects a high frequency detector with

. It checks the resonant frequency of L1 while changing the frequency of the dip meter. When different from the planned frequency (about 83 MHz) extremely, it changes the value of C1. Because there is not an amplifier in the part of

, the voltage is small. So, the circuit tester which is connected with the high frequency detector should be set in the voltage range as small as possible. But, it is necessary to pay attention in the surplus of the voltage to prevent circuit tester's breaking. Because the voltage of

is small, it doesn't have to adjust, being detailed.

Adjustment of L2

Next, it connects a high frequency detector with

and it adjusts L2. When changing the value of C1 in adjustment of L1, it makes C2 the same value too. Because there is a high-frequency amplifier before

, the output voltage becomes higher little than

Adjustment of L3

Next, it connects a circuit tester with

and it adjusts L3 as previous. Because the voltage of

is changed into the direct current by the diode, it can not connect a high frequency detector.

I made the value of C3 1pF less than C2. The core fitted the top of the transformer at this value.

Last adjustment of the resonant frequency

It stops the oscillation of the dip meter and it brings the coil of the dip meter close to the coil of the transmitter. While turning the dial of the dip meter, it checks the point where the needle of the meter moves. The frequency is the oscillation frequency of the transmitter.

Making do the operation of the oscillator of the dip meter without changing the position of the dial. It brings an antenna with receiver close to the coil of the dip meter. It connects a circuit tester with the position of

, it adjusts L1, L2 and L3 in the order and the voltage of

maximizes. The electric wave of the transmitter can be used without using a dip meter, too. Because the transmission frequency changed when the transmitter made do long operation, I used a dip meter.

It confirms that it receives the electric wave of the transmitter after the adjustment by the dip meter ends and that voltage is gotten at

Confirmation of the comparator output

It connects a circuit tester with the 7th pin of IC1. It confirms that it becomes 0V when not receiving an electric wave and it becomes +5V when receiving an electric wave.

Above, all adjustments of the receiver are ending. After this, it loads PIC and it confirms the operation of the relay and the lighting-up of the LED which corresponds with the transmission code.
I mounted PIC and confirmed normally operation.

Sensitivity with receiver

The sensitivity with the receiver which was made this time isn't good. I can not measure sensitivity because I don't have a measurement receptacle. Approximately hereinafter.

It puts a 1-m antenna to the receiver and it puts a 20-cm antenna to the transmitter. As for the distance between the receiver antenna and the transmitter, about 1m is a limit.

It seems not to be practical. However, I think that it can be used for the control of the door or the control of the security lock and so on. In this case, there is not high receiver sensitivity, being needed. (Excusing)

At first, I thought that it was possible to control from the place to have left by about 5m. It was impossible.

Because the receiving sensitivity which was hoped for wasn't gotten, I think that I will make the receiver which used IC for the FM receiver.