Electronics Lab Philippines

MIYAMA MYK-AM1021C

MIYAMA MYK-AM1021C
« on: February 17, 2020, 07:12:19 PM »
Nakabili po kami ng radio kit sa deeco. Yung MIYAMA MYK-AM1021C. Kasama po kasi sa project namen na dapat maidentify namin yung per block ng radio. Like kung san yung RF stage, oscillator, mixer, IF amplifier, detector, and audio amplifier. Pwede po pahelp. Papalitawin po kasi dapat yung mafoform na signal sa oscilloscope per stage and hindi po namin alam san banda yung mga stage nayon

Offline backy27

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Re: MIYAMA MYK-AM1021C
« Reply #1 on: February 17, 2020, 07:29:44 PM »
Nakabili po kami ng radio kit sa deeco. Yung MIYAMA MYK-AM1021C. Kasama po kasi sa project namen na dapat maidentify namin yung per block ng radio. Like kung san yung RF stage, oscillator, mixer, IF amplifier, detector, and audio amplifier. Pwede po pahelp. Papalitawin po kasi dapat yung mafoform na signal sa oscilloscope per stage and hindi po namin alam san banda yung mga stage nayon

Hintay tayo sa mga expert po dyan sa radio ..pero madalas ko mabasa dito si sir bravokilo isa yata sa expert dyan..  ;)

Re: MIYAMA MYK-AM1021C
« Reply #2 on: February 17, 2020, 07:34:56 PM »

Re: MIYAMA MYK-AM1021C
« Reply #3 on: February 17, 2020, 07:37:49 PM »
Hintay tayo sa mga expert po dyan sa radio ..pero madalas ko mabasa dito si sir bravokilo isa yata sa expert dyan..  ;)

Thank you po, nasend ko na din po yung schematic na kasama po ng kit

Offline danny

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Re: MIYAMA MYK-AM1021C
« Reply #4 on: February 18, 2020, 08:44:59 AM »
Antayin natin si bravokio

Offline Johannah Aleksandria

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Re: MIYAMA MYK-AM1021C
« Reply #5 on: February 18, 2020, 10:15:47 PM »
May nakalagay naman yata sa schematic.
Ang alam ko pula yung oscillator.,  puti, dilaw at itim yung IF stages at bawat transistor pagkatapos ng IF transformer ay IF amplifier.
Yung detector yung nag-iisang diode (4148). Yung audio amplifier nya ay yung IC.
RF stage yung kabilang ang antenna at variable capacitor., at yung transistor ay yung mixer.
Yung feedback resistor na 4.7k ay para sa AGC.
Generations come and generations go, but the world stays just the same. What has happened before will happen again.

Re: MIYAMA MYK-AM1021C
« Reply #6 on: February 19, 2020, 08:49:10 PM »
May nakalagay naman yata sa schematic.
Ang alam ko pula yung oscillator.,  puti, dilaw at itim yung IF stages at bawat transistor pagkatapos ng IF transformer ay IF amplifier.
Yung detector yung nag-iisang diode (4148). Yung audio amplifier nya ay yung IC.
RF stage yung kabilang ang antenna at variable capacitor., at yung transistor ay yung mixer.
Yung feedback resistor na 4.7k ay para sa AGC.

Thank you po sa pagsagot, God bless po

Offline bravokilo

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Re: MIYAMA MYK-AM1021C
« Reply #7 on: February 19, 2020, 10:03:45 PM »
Hello friends. andito ako, medyo late.hehe.

Offline bravokilo

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Re: MIYAMA MYK-AM1021C
« Reply #8 on: February 19, 2020, 11:02:11 PM »
http://bkamradio.blogspot.com/

Yo might want to read my blog on AM radio but what you need is a conceptual explanation first. I have it somwhere and yu can click my name, then click the history of my posts. Pero, short of that, let me try dito na:

History of Radio Receiver

     I think it was Faraday who demonstrated radio waves. Just google. But it was Maxwell who wrote a dissertation on radio. He said we can transmit info via radio waves.

     You will read a lot about receiving waves and the first one was using a "cat whisker", a fine wire touching a galena crystal.  then they say that this was replaced by the vacuum tube diode whic ws considered a big leap for man. In ships, the cat whiskers moved with the waves. The tube diode did not. WOW! He ganged tw

    But wait a minute, if they were using whiskers to receive, who was transmitting and how? There was no device to create an oscillator yet. THEY WERE SENDING SPARKS!

     Have you ever heard a motorcycle's sparks from its  plugs in your car radio? You heard the sparks. That was what Marconi used to transmit from Europe to America. The spark gaps was high above the ground. A mechanical vibrator generated the spark. We can make on today using the car ignition coil and a mechanical vibrator.

     So, it was grrrrrrrrrrrrrrrrrrrrrrr. How did put information? They stopped the continous waves l form short and long grrrrrr.
MORSE CODE! It as CW which is still used by hams today.

     Edison started it all. He invented the light  bulb and it found is way to Fleming in UK. He experimented with it and found out that electrons flowed from the filament to a nearby wire (later called the plate) inside the tube. THE DIODE!   This invention went back to America and there, it was discovered that a wire in between the filament and the plate can control the flow with a tiny current. THE AUDION, THE FIRST TRIODE.

    Armstrong worked on the receiver. Meanwhile, the transmitters were no longer spark gaps but electronic oscillators using the audion tube and coils to determine frequency.

     Armstrong popularized the Regenerative receivers where the received signal was fed back into the tube amp and regenerated What followed was the TRF, a series of coils and tuning capacitors. But there were too many tuning capacitors. Armstrong reduced it to just ONE !

THE SUPERHETERODYNE RADIO

     Armstrong knew that frequencies can be added and subtracted when mixed. He though that if he can have a variable oscillator in a radio which frequency can be mixed with the incoming signal, he can fix the differential frequency(the difference) to just one frequency.  His RF amplifiers can be tuned to just that one frequency. By is time, voic was alady transmitted over the air.  Voice manipulated the strength of the signal which is changing the AMPLITUDE of the signal. Thus AMPLITUDE MODULATION.

      A convention was developed that the differential frequency be 455 khz, called the intermediate frequency or IF. Probaby because the medium wave band was already chosen as the ideal band to use, from  540 KHz to 1640 Khz. Armstrong's
superhet radio had an oscillator which tunes to 455 khz below the incoming signal. Thus the IF transformers are all tuned to 455 khz.

Offline bravokilo

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Re: MIYAMA MYK-AM1021C
« Reply #9 on: February 20, 2020, 12:03:45 AM »
Now we are ready for t he Miyama radio.

Where is that local oscillator? The red can. See the second tuning cap in the tuner connected across its terminal on  the three pin side. The local oscillator needs a tranny to oscillate, thus it uses the first tranny. See the center pin of the LO coil connected to the emitter of the tranny via a small cap. Now look at the 2 pin side, the signal from the collector goes thru it and induces th signal to the CT of the 3 pin side. The coil  will oscillate and the freq. will vary when the tuner is moved.

Where is the incoming signal? It is in the antenna coil in the ferrite bar. Note the tuning cap across the antenna coil to tune it. A short secondary coil in the f. bar sends the signal to the base of the first tranny via a small cap to prevent shorting the base to ground. The incoming signal is MIXED with the local oscillator in the same tranny. In the past, a separate tranny was used for the local osc. but it was soon realized that this was not necessary.

THUS, THE FIRST TRANNY IS A MIXER-OSCILLATOR TRANNY. The differential frequency will always be 455 khz. called the Intermediate Frequency or IF.

Take note, the collector runs through the LO and the the yellow IF transformer or IFT. Since the yellow can only amplifies 455 KHZ, it rejects frequencies above and below it. The IF frequency is further amplified by the second tranny which signal is fed into the white IFT which is also fixed tuned to 455 Khz. And one more time by he 3rd tranny and the black IFT. The radio becomes very SELECTIVE AND SENSITIVE.

WE CANNOT HEAR RF!

We cannot hear the RF signals which is now strong at the black IFT. Human hearing is about 1 KHZ and 455 KHZ is way above our hearing. That RF signal is also AC!

We want to hear the changing amplitude which carries the music. We can do this by converting the AC to DC by using a diode. At DC, it is fluctuating in strength , (THE AMPLITUDE). THIS IS THE VOICE OR THE MUSIC!

So, the diode is the threshold separating the AC from the fluctuating DC. Anything after the diode is now AF.(audio frequency). The IC is an audio amplifier to drive a speaker.

Offline Ikasamoko

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Re: MIYAMA MYK-AM1021C
« Reply #10 on: February 20, 2020, 08:22:48 AM »
I hope tama pa memory ko :D


Offline bravokilo

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Re: MIYAMA MYK-AM1021C
« Reply #11 on: February 20, 2020, 10:13:43 AM »
KOREK KA DYAN!

Offline Johannah Aleksandria

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Re: MIYAMA MYK-AM1021C
« Reply #12 on: February 20, 2020, 07:11:05 PM »
Importante din yung AGC sa palagay ko.
Generations come and generations go, but the world stays just the same. What has happened before will happen again.

Offline bravokilo

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Re: MIYAMA MYK-AM1021C
« Reply #13 on: February 20, 2020, 08:16:00 PM »
Ah yes. Again, conceptual muna. RAdio stations do not only vary in trnsmitting power but also are of different distances from he radio receiver. Stronger/nearer stations will come in booming and weak one will come with the volume low. hre must be a way the radio can adjust automatically. If only the volume level can be a reversed bias to the amplifiers, the radio can do just that. Fortunately, after the diode, their is a DC current there which can be sent back to the amplifiers. Take note the trannies are NPN and the reverse bias should negative. Op0ps,oops,oops.....he diode position in the diagram is wrong! It should be reversed. After the correction, the diode output to the volume control and amp. will be more negative for strong stations.  See the 470  and 47k in series where the negative is connected back to the base of the second tranny via the secondary of the IFT.

Offline bravokilo

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Re: MIYAMA MYK-AM1021C
« Reply #14 on: February 26, 2020, 01:53:17 PM »
WHAT HAPPENED TO ISABELLA? NAGPUNTA SA ISABELA, MALAYO. NAWALA! LE'S WRITE FINIS TO THIS CASE.

Offline Ikasamoko

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Re: MIYAMA MYK-AM1021C
« Reply #15 on: March 14, 2020, 11:19:29 AM »
Baliktad nga yung diode. :D