WildCat FM /technical station.
attic of station's chief /Top floor /White Room
FM stereo matrix generator /3

Can the operation of the circuit be understood though production is advanced
with Step by step with the verification of each circuit ?
The power supply of this experimental circuit uses a good quality about single power supply of 12V/100 mA in capacity.

Production of Pre-emphasis /input filter/buffer amplifier circuit
 

Well,
Last center department Balanced modulator is a very, and most important part in FM modulator of the matrix type. it doesn't advance it previously in the future because it is useless no matter what it does later if it doesn't operate correctly.

This circuit attacks the filter part of the voice input. An absolutely necessary by all means circuit doesn't include the filter circuit of this though it is a fellow for FM modulator by a so-called MPX filter.

However, in "Standard how to transmit the frequency modulation broadcasting" of Radio Law In the standard for the main channel signal 0Hz-15000Hz

it is necessary to control the upper bound of the voice frequency in some shape within 15000Hz.
 
 

it saw making it in feelings this time, and to avoid the interference with the stereo, the pilot signal, and the audio signal, the purpose of this filter is put.

There is basically a problem in another part actually though it is said as the audio signal and the pilot signal interfere if this filter doesn't exist, the stereo indicator is blinking, and the modulation level is not raised and it is likely to lead to a little problem evasion between a lot of mini FM station. The pilot signal of the modulation part of the transmitter for mini FM sets up the audio signal easily with the interference with higher-order because the signal purity is low and the problem happens. The signal generator hardly obstructs an original pilot signal directly in a usual audio signal (CD or MD etc.) as long as it doesn't use it, too.

In a standard FM modulator even if there is no filter The thing that the indicator is blinking is not in the overmodulation level of about 200% either.

Because it is a place that relates to the filter, the easy explanation of the causal relation,
"Cause 1"
the pilot signal of the toy transmitter for mini-FM, and the subcarrier signal are signals that following rectangular wave mutate almost, and this signal is interfered by an extreme distortion's hardening and a large amount of spurious diffuses even to suitable and the voice signal region.
 

pilot signal and band spurious of general "Toy transmitter" (800KHz span +/-400KHz)
Because the pilot signal has been extremely distorted The width of the electric wave has abnormally extended to the state without the signal.
  Bad example of signal
 

Subcarrier signal of general "Toy transmitter" (MPX signal)(AF_signal /1KHz) The mutual interference of the harmonic component happens because the subcarrier has been distorted, too though the subcarrier stands up by the voice input. it is correct and the audio signal is incommunicable in the vicious circle of the diffusion of the band in case of it is because the subcarrier has been distorted.of general "Toy transmitter" (MPX signal)(AF_signal /1KHz)
The mutual interference of the harmonic component happens because the subcarrier has been distorted, too though the subcarrier stands up by the voice input. it is correct and the audio signal is incommunicable in the vicious circle of the diffusion of the band in case of it is because the subcarrier has been distorted.
  Bad example of signal
 
I think that it can understand the thing that correct voice information cannot transmit from this abnormal signal if it compares it with the signal wave form of matrix generator explains on the above-mentioned signal and this page.
 

it interferes and it huge spurious to voice region diffuses each other physical the harmonic component the signal generated higher-order mutually though generated only in higher-order (The thing which the frequency is low and near also sets off a vicious cycle). In the worst case, it is likely to hear of the interference beat sound depending on spurious of the pilot signal in the state of a no sound.

it interferes violently between spurious and the voice signal diffusing of this and an original pilot signal is obstructed. The tuner received because the pilot signal that the signal purity is bad cannot originally identify the signal, and causes the blink of the stereo indicator easily.
 

The pilot signal should be a sine wave originally signal.
Because neither the harmonic component nor spurious exist as the sine wave signal without the distortion as knowing is theoretical.

Is the explanation strange ?
Neither the harmonic component nor spurious exist theoretically for a theoretical sine wave signal, and it is correct this.
spurious appears because the sine wave signal physically made has not perfection but a little distortion.
The existence of spurious is a little like a complete sine wave signal. In short, you only have to distort and not to exist.

it seems to be hardly significant even if this filter is put as long as a basic part is not improved.
Were you able to understand somewhat?¤
Basic part improvement cause other chance.!!
 
 
 

it is used the purpose of this filter to avoid the minute interference beat between the stereo, the pilot signal, and the voice signal, and is an improvement of the quality in the high region signal, and is a reduction of the distortion, etc.As an original dimension, is because it is the interference the pilot signal of the sine wave without the distortion and between the voice signals, it Yo considerably HiEND field ?

it is good for externals in this though it is "Dasai" considerably circuit.
The filter of 19KHz is turning the use of the circuit designed before, and it resonates by L and C and a target frequency is attenuated at a dash. I think that it is a circuit that is far smarter to increase the number of IC meaningless multi using the OP amplifier and repeating and filtering and to cause the tone quality deterioration. The phase characteristic is excellent up to the frequency that attenuation starts and the amount of attenuation is obtained enough.
Ideally, it drops like 15KHz precipice, the frequency thereafter is passing and only because the vicinity of the pilot signal of 19KHz is attenuated, an enough effect is achieved without.

An enough characteristic is obtained by one step by uniting two steps this time. I also go from making also by and see ?

it is necessary to resonate and because the attenuation characteristic is obtained, to adjust it. The signal of 19KHz is put from the signal generator in the voice input, the core is adjusted alternately several times for the turning attenuation point, and it matches it to the maximum attenuation point.

frequency response with of a filter single goods and it saw.

There is not wonderful undulation and either the tune point of 19KHz has dropped by about -50dB.
 
 

In a filter single goods, limited characteristic it is not a good thing as the audio circuit that the OP amplifier is easily multi used and increases the number of extra, active elements that can be called having a considerably troublesome part in the problem of the circuit impedance when Pre-emphasis twines though canceled when the buffer with the OP amplifier is put to evade this.

The influence comes out in the frequency response in a selfish place where the agreement is put whereabouts, and the change in tone quality takes place. The characteristic became in Pre-emphasis and the filter's crowding became bitter feeling because it thought about the thing used by separating Pre-emphasis this time though an integrated characteristic excellent when "match technique" that went out was used was obtained.
As for a detailed thing, the next homework is made a thing.
 
 

Following frequency response finally.
 

Attenuation characteristic of filter and Pre-emphasis error margin in high region

Because FM straight line detector (ando/RDA-203) had the De-emphasis ideal characteristic of 50ƒÊs and 75ƒÊs, the following characteristics were taken.
it is putting the difference of 1dB as seen easily.

Pre-emphasis /OFF to De-emphasis /OFF (RDA-203)
Pre-emphasis(50us)/ON to De-emphasis(50us)/ON (RDA-203)
Pre-emphasis(50us)/ON to De-emphasis(50us)/ (SONY A5-ES)

Mutually, the error margin in the state characteristic and Pre-emphasis in the through state of it as for the emphasis/to pass De-emphasis has been installed on 0.5dB or less.

SONY SA5-ES used as a reference tuner of FM also has little difference between SA5-ES and (ando/RDA-203) for the characteristic of De-emphasis though took the characteristic. This time, thing I see with the De-emphasis characteristic of the ideal as a reference tuner though the difference of about 10dB is seen with 21KHz because SA5-ES has the high region filter of 19KHz or more though first (SONY SA5-ES) and (ando/RDA-203) were compared.

Homework in the thing though it is anxious that the corner of attenuation is sweet whether the characteristic of the extent that can be used is made of securing though the story wandered a little it is Ne though is anxious and is not possible to know because it sees in the graph of a linear characteristic. it becomes feeling in the figure below if it sees in the log graph where a usual audio characteristic is displayed.

It puts it from the overall viewpoint in (10Hz-15000Hz +/- 0.5dB) or less I want to put it in (+/- 0.1dB or +/- 0.2dB) or less if it sees audio and severely though it is settled. Experiment is done this time.
 

To catch the frequency response of the emphasis and the filter If there are a low frequency transmitter and VTVM, the characteristic can be confirmed though time hangs. it only has to correct the voltage by the spot frequency according to the table of the measurement emphasis and to write the plotting characteristic curve on Hira logarithm graph paper.

it was necessary to have done by this method in all old times when the frequency response was caught.
 

The circuit is completed only by passing the amplifier of the minimum requirement from Pre-emphasis and the filter circuit to double balanced mixer IC SN76514.

The number of amplification amplifiers is not excessively increased and there is a necessity for raising the gain. it is thought conversion from a standard output of the mixer and enough in about +2 or +3dB. Professional input volume raise use provide maximum value squeeze use basic idea.

it only has to be able to secure the gain of the extent that can be absorbed when the balance collapses.

A final filter and the buffer amplifier circuit become such feeling.
L in the filter part connects and uses MPX coil/MPX19T of Toko, Inc. like the example as shown in the figure below.

The MPX coil series of Toko, Inc. is a convenient coil that can be used for the color usage when the connection method etc. are devised.
 
 
 

Well, please connect the experiment modulator of this matrix type with VCO next time, it pursues the subject while seeing a final characteristic etc. , and prepare VCO to which experiment performance can be output and do the following preparation.
 

Do you break out ?
This page is already room and that top floor is white because it adheres to these times and there is a person who was able to come in the head white.
 
 
 

Next Page /the experiment and see !?
FM stereo matrix generator /4  Connection to VCO/exciters and phase of pilot signal
 
 
 

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