WildCat FM /technical station.
attic of station's chief /Top floor /White Room
FM stereo matrix generator /4

Production is advanced with Step by step with the verification of each circuit.
Let's be not in a hurry and understand the operation of the circuit.

The following measuring instruments are necessary to verify FM modulator explained on this page experimenting.
VTVM FG (high impedance voltmeter/ACorDC)
Function generator
oscilloscope (in real time store)
Linear detector (FM LINEAR DETECTOR).
The power supply of this experimental circuit uses a good quality about single power supply of 12V/100 mA in capacity.

Connection to VCO/exciters and phase of pilot signal
 

The sound is emitted though it depends on the modulation sensitivity of VCO if the last circuit operates well if it connects it with exciters.

Let's put the buffer with the OP amplifier temporarily as follows and connect it with VCO.

Sensitivity is different because of VCO and adjust for an appropriate modulation level to go out, please. When the modulation level doesn't go up, you may change return resistance RA of the OP amplifier to a suitable value, adjust for an appropriate modulation level to go out, and put VR etc.

Well, because the modulation level changes depending on the frequency when there is Pre-emphasis up to the end of a general test and the measurement, the capacitor of the emphasis is removed from the circuit though experiment of this time matrix generator is finally connected with VCO and it tests as shown in the figure below.

FM Linear detector s used to connect with VCO and to measure the signal to get on the air. The RF signal from VCO(FM exciters) is connected, and suitable ATT is put, the signal level is matched, and the signal from FM straight line detector is connected with the oscilloscope. The trigger is used properly according to the condition though it is thought that it understands because it does by the last measurement.
 

it modulates correctly in the synthesized MPX signal in the place where the measurement environment was changed or it measures it. Audio signal (AF_signal) of about 1KHz is put in experiment Herr/matrix generator, and it sets it to about 50% while seeing the modulation level with a straight line detector.
A similar MPX signal to "CHECK-2" done in the paragraph of "Balanced modulator " should be able to be observed if there is no problem in VCO(FM exciters).

1KHz AF_signal /L ch signal of promotion image
    
Because the modulation circuit of the matrix type has synthesized the of Pure signal differing from the modulation circuit of the "SW" method first, an extremely clean signal is promoted without the filtering processing.

When the shape of waves has mutated slightly by VCO(FM exciters), it readjusts according to last time. When the signal cannot be correctly reproduced even if it adjusts it though an accurate to some degree signal had come out in the last state, it is necessary to correct VCO so that a correct modulation may hang or to change it into VCO by which a straight modulation is multiplied because there is a problem in VCO.

it verifies it in each frequency when it can be adjusted that a correct MPX signal comes out by the audio signal of 1KHz.

Especially, please put, test the audio signal of each frequency, and whether neither the low region signal of 50Hz or less nor the high region signal of 10KHz or more have mutated look. 10Hz
it is necessary to install the change of a wavy level of the modulation level and the oscilloscope with a straight line detector between up to 15000Hz within about 0.5dB.
 
 
 
injection of pilot signal and phase suiting with subcarrier.!
 

If there is no problem in each frequency like the above-mentioned The circuit that does the pilot signal of 19KHz in MIX is added and the pilot signal is injected.
 

When the circuit can be added, the cooking stove of a straight line detector is set and the level of the changing pilot signal is set to 8-10%) and several Frequency Deviation (6-7.5KHz) temporarily.

Whether the shape of waves of the pilot signal is distorted by the oscilloscope is confirmed.

When the pilot signal can be injected, it is necessary to phase it to the subcarrier of 38KHz.
The phase of the pilot signal with the subcarrier is extremely important.
The line doesn't obtain a straight stereo Separation characteristic in each frequency if the pilot signal is not suitable for the phase of the subcarrier even though an excellent signal characteristic is obtained by the straight line.
Moreover, it is restricted to "Quality of the electric wave in the frequency modulation broadcasting" of Radio Law, saying that "Within +/- 5 degrees of pilot signal phase allowance deflection

Well, there is variously how to confirm the phase of the subcarrier and the pilot signal.
Various ways are in the technical book to the content recorded in the inspection metrology of the transmission equipment of the one that the translation by a great scholar teacher is not understood theoretically explained

Both are only the extremely ways.

it explains by this way this time because the method of recording in the manual of orban optimod 8100 is easy comparing it. (Refer to 8100A1 Manual_Section_4/4 page. )

1KHz AF_signal/(SUB)/opposite phase signal is put in L and R channel of the voice input like the following measurement environment, it observes with the oscilloscope, the coil of 19KHz/19T is matched, and the center of the crossing point of the turning signal is matched.

The audio signal is confirmed, and when the coil is turned, the peak value corrects the stop pilot signal level, and puts audio signal (SUB) again and confirms the phase because the gap signal level changes slightly.
The pilot signal level is 8-10%, and Uts 6-7.5KHz in regulations of Radio Law cycles several bias The modulation level of the pilot signal is confirmed with Deviation of a straight line detector.
 
 

The settings were matched, reproduced, and seen as much as the image recorded in the manual of orban.
The measurement uses the storage mode together.

it is a right measurement image to have expanded the crossing point of a left measurement image.
    
The signal wave form can be reproduced in this experiment modulator almost similarly though there is will being not to trail one's coattails to the modulator of orban optimod 8100.
 
 
 
 

Because the phase is not suitable when it is the following, it is necessary to readjust.

Separation is deteriorated to the signal excellent in 5-10dB because of the gap of such a phase.
 
 

The phase of the pilot signal with the subcarrier is extremely important as recorded in the preceding chapter.
PLL is used in the NEC-FBN9000 series etc. in the modulation part and the domestic production of famous orban optimod 8100 to always keep Separation to be steady. If the phase of the pilot signal with the subcarrier is locked with PLL, supplying a sound steady under all the environments becomes possible. PLL is installed in the modulation part of the transmitter that WildCat FM uses for about eight years. WildCat FM becomes the modulator experimentally explained here and installing PLL becomes one of the conditions it will be possible to do the practice use.

At this point if the phase of the pilot signal with the subcarrier is suitable. When it is a straight FM tuner, Separation of 50-55dB or more is sure to be obtained enough.

 
 
 

Please return based on the connection of the capacitor of Pre-emphasis input the voice from the mixer, and enjoy even music.

The next experiment verifies the signal modulated by this modulator from the side of the electric wave and examines the circuit.
 
 
 

Next Page /it advances to the following experiment
FM stereo matrix generator /5  FM stereo modulation signal Spectrum seen from side of electric wave
 
 
 

FM stereo matrix generator  introduction
FM stereo matrix generator /1  Production of pilot signal and subcarrier generation circuit
FM stereo matrix generator /2  Production of L-R, L+R circuit, and Balanced modulator circuit
FM stereo matrix generator /3  Production of Pre-emphasis /input filter/buffer amplifier circuit
FM stereo matrix generator /4  Connection to VCO/exciters and phase of pilot signal
FM stereo matrix generator /5  FM stereo modulation signal Spectrum seen from side of electric wave
 
 

document of yamamoto by WildCat FM