 Sebelum beberapa bulan lalu, saya mempunyai sebuah bahagian yang berlaku. Ia disebut DME dari klub penyelamat saya. Di luar kelihatan, saya mempunyai dan melihat apa yang berlaku di dalam dan bagaimana ia berlaku. Sebenarnya ini adalah sebuah bahagian yang terlalu kompleks yang mempunyai. Saya sebenarnya perlu melewati sebuah teori sebelum anda faham kenapa ia disebut. Jadi, DME berlaku untuk membuat peralatan yang berlaku. Jadi, sebagian yang dikenali adalah membuat peralatan yang berlaku. Jadi, bagaimana ia berlaku? DME ini adalah menghidupi di sebuah bahagian. Jadi, anda mahu menemukan peralatan ke sebuah bahagian. Jadi, ia berlaku. Bahagian pertama, ia menghidupi sebuah bahagian ke sebuah bahagian. Kemudian bahagian akan berlaku. Jadi, berdasarkan peralatan ke sebuah bahagian yang berlaku, dan sebuah bahagian yang dikenali, bagaimanapun, DME ini dapat menjadikan bagaimana jauhnya peralatan ke sebuah bahagian ini. Jadi, tentu saja, ada beberapa peralatan ke peralatan ke sebuah bahagian ini. Jadi, tak boleh ada keputusan antara peralatan ke sebuah bahagian dan ke peralatan ke sebuah bahagian. Yang lain adalah, ini sebenarnya sebuah bahagian. Kerana anda sebenarnya memegang peralatan dari peralatan ke sebuah bahagian ini. Jadi, dan bahagian yang rambut mengalami keputusan ini sebenarnya, ia bukan peralatan ke sebuah bahagian. Contohnya, berharga di praktik, bahagian tinggi di sebuah bahagian ini adalah lebih kecuali ke peralatan ke sebuah bahagian. Jadi, sebenarnya, ia hanya tidak berbeza dalam peralatan tersebut dan peralatan ke sebuah bahagian. Jadi, peralatan ke peralatan, Mereka sebenarnya banyak orang, di sekitar dunia. Untuk DMA, mereka biasanya dihidupi dengan sebuah tempat yang lain. Jadi, ada dua pilihan pilihan pilihan pilihan pilihan. Seorang adalah POR. Ia adalah radio yang sangat tinggi dan kemudian daripada TAKAN. Jadi, TAKAN adalah menggunakan pilihan penerbangan. Jadi, DMA adalah sebuah tempat yang biasanya dihidupi dengan sebuah tempat ini. VOR dan TAKAN, mereka memberi informasi yang diberikan untuk pilihan penerbangan. Tapi, jika kita tahu pilihan penerbangan untuk sesuatu, tetapi kita masih tidak tahu seberapa segera. Jadi, itu di mana DMA datang. Jadi, apabila anda mempunyai pilihan penerbangan, anda tahu seberapa segera dari pilihan penerbangan, anda tahu di mana pilihan penerbangan. Jadi, untuk DMA, mereka menggunakan pilihan pilihan ini. Jadi, mereka menggunakan dua pilihan separa untuk menjawab untuk menggantikan pilihan penerbangan sehingga menggantikan pilihan penerbangan. Jadi, mereka menggunakan pilihan ini. Tapi, untuk DMA, mereka menggunakan pilihan sedikit kecil, lebih berkumpul dengan pilihan yang dihidupi oleh DMA. Dan pilihan penerbangan tersebut juga sedap sempurna, anda tahu. Jadi, apa itu? Kerana pilihan penerbangan dan pilihan penerbangan, mereka berada di pilihan pilihan pilihan pilihan pilihan pilihan pilihan. Jadi, mari kita kata, jika pilihan penerbangan tersebut menggantikan pilihan penerbangan 1.025mHz, jika anda menggunakan pilihan penerbangan X, anda akan menggantikan pilihan Pilihan Black at 9.62mHz. Dan sehingga, anda dapat melihat. Jadi, DMA menggunakan dua pilihan penerbangan. Jadi, saya akan berkumpul dengan itu. Kenapa mereka menggunakan dua pilihan separa? Jadi, sekurang-kurang 1,000mHz. Pilihan penerbangan ini sangat besar, tapi maksudnya, ia bermakna ada pilihan penerbangan dari VOR ke DMA. Jadi, ingatlah yang saya katakan, ini sebenarnya adalah pilihan penerbangan. Jadi, untuk VOR, VOR sebenarnya menggunakan beberapa pilihan penerbangan untuk menggantikan pilihan pilihan Pilihan Pilihan Pilihan. Jadi, sejak mereka selalu menggunakan pilihan penerbangan, mari kita kata, anda dapat melihat pilihan ini. Jadi, ini adalah pilihan penerbangan VOR. Jadi, ini adalah pilihan pilihan penerbangan. Apabila ada pilihan penerbangan VOR, bagi contoh 1,08mHz, ini adalah 1,08mHz di sini, pilihan Pilihan Pilihan Pilihan Pilihan DMA ini adalah 1,041mHz. Dan pilihan penerbangan Pilihan Pilihan Pilihan Pilihan Pilihan ini adalah 9,78mHz. Jadi, dua pilihan ini adalah sekurang-kurang 63mHz. Jadi, sehingga Y ada X dan Y, sebabnya X bermaksud pilihan penerbangan VOR dengan 0.00. Dan Y bermaksud pilihan penerbangan VOR dengan 0.05. Jadi, ada pilihan penerbangan FIX. Jadi, apa tentang Singapura? Jadi, Singapura, kita sebenarnya ada beberapa pilihan seperti itu. Jadi, saya akan berjumpa dengan apa yang ini 5. Jadi, untuk pilihan pertama, pilihan Pilihan Pilihan Pilihan Pilihan DMA ini adalah Pilihan Pilihan Pilihan Pilihan. Itu sebenarnya pilihan penerbangan VOR. Jadi, mereka ada pilihan penerbangan VOR dengan 1,051mHz. Kita dapat lihat ini adalah pilihan penerbangan, kita dapat lihat 1,051mHz di sini. Jadi, pilihan Pilihan Pilihan DMA bukan mengubah ke pilot, tapi sebab ada pilihan penerbangan FIX, ia adalah diberi. Pilihan Pilihan Pilihan Pilihan Pilihan Pilihan Pilihan Pilihan Pilihan Pilihan Pilihan Pilihan Pilihan Pilihan Pilihan Pilihan. Kemudian kita ada dua lagi. Satu lagi di Tegong dan satu lagi di Sinjong, di Sinjong, bermaksud di Jons Island. Jadi, kita dapat lihat ini adalah pilihan ini di sini. Seperti yang lain, ini dua adalah lebih spesial. Mereka sebenarnya adalah berbicara. Jadi, ini adalah pilihan penerbangan yang membutuhkan. Satu lagi di Tegong dan satu lagi di Sinjong. 1,3.9x1,16.3x1.6. Jadi, dengan sebuah sewaja 5 bikin DMA, jika kita Watch the Pilot di Singapura, kita boleh gunakan untuk mengenai bagaimana rata dari perut, dan dari ibu bantuan. Jadi, bagaimana ia melihat itu? Jadi, ini adalah berita tersejarah di perjalanan. Jadi, sekarang, ia masih ke 116.3x1.6x1.6.3x1.6.3x1.6x1.6x1.6x1.6x1.6x1.6x1.6x1.6x1.6x1.6x1.6x1.6. It's actually the VOR frequency of Philebi Abyss, but the equipment doesn't use 116.3. 116.3 is just a shorthand. Internally, it knows what is the mapping to the associated DME frequency. So now you look above the DME, this is actually a GPS you need. So you can see that this aircraft current position is here. So this is currently above the waypoint SETI. So SETI is here. So if let's sit down the current act, the currently the aircraft is here, it's about 5.1 nautical miles away from Philebi Abyss. Here, it's about 5.1 nautical miles away. So you can think of it as times 1.82. You can get a how many kilometers. So this is how the interrogation process looks like. So when the aircraft wants to talk to a DME station, it will send a pair of pulses. So each pulse has a wave of 3.5 microseconds at a fixed spacing of 12 microseconds. So the DME station is perpetually listening. So whenever it sees that or that 2 pulse pairs are directed at it, it will wait 50 microseconds delay and then it will reply back to the aircraft at the associated reply frequency. So the aircraft will then know base of this delay how far away it is. So this is how the equipment looks like from the back. To the technician, they will usually consult a maintenance manual like this. So you can see these are the pins, the output pins of the DME. So to power it, they will consult on this particular table here. You can see it requires 14 to 28 volts of voltage, power input, and then it can end the ground as well. So it can accept 14 to 28 volts to power this. So with that, I decided curious what's inside. So I opened up and this is the first thing that I see. So you can see that on the left is just one big circuit board and then here we have an RS section. It's a completely shielded. It's in the metal cage. So before I went deeper into the teardown, I looked into the maintenance manual to see what's the system architecture. So you can see this is extremely centralising. There's one microprocessor here. It actually should become microcontroller and everything else, the RS section, everything will connect to it in the display as well. Okay, so let's first start with the microcontroller. So I googled what is this part-time over there and then I found out that it's actually made by this company Mostach. Mostach is already ported over by ST. So that's why you can see that ST logo here. Okay, so we can see that it's relatively preparative compared to whatever we have today. Quite old, 1977. Okay, so okay, then the next thing is the first impression 55. So let's see. So this is the device power on in the plane. You can see that the display is not constant. There is some kind of interliving in the display. So of course that got me curious in, okay, this is because of the camera fabric. In actually, when you use a naked eye and see, you wouldn't be able to perceive this flickering. So when we open up, I can see this is see that each of these have their own segments. Okay, so based on what the maintenance manual says, right, this interliving of the display is actually deliberate. They do not show it in a straight sequence 1, 2, 3, 0, 1, 2, 3, and so on. They actually do it in autonomous, 0, 3, 6, 1, 4, 7, 2, 5. 0, 3, 6, 1, 4, 7, 2, 5. Right, so that the human eye will be unlikely to perceive this flickering. Very interesting. Okay, so for this particular display, it's actually something called gas discharge. It is not an LED display. So in that time, LED display, I don't think it was common. I'm not sure whether LEDs were invented at that time, 1970s. But in order to have a very bright display that can be seen by the pilot under all lighting conditions, they had to use a gas discharge to ensure it's bright enough. So the footage that they typically operate at is minus 100 to 100. Very high voltage DC. So at least car or higher level voltages, it's not possible for the microcontroller to drive them directly. So that's why they have actually a few drivers. So okay, the first thing is that we want to select which digits you want to control any one time. Because remember, there are several digits here. And if you have so many control lines to it, the microcontroller will not have enough lines. So they actually had to select select it and drive them one by one. So and they are actually eight digits inside. They actually use a combinational logic multiplexer. So they just use three lines and they control eight lines to determine which of the eight digits they want to control at a particular time. Then after that, there is actually common anode U315. So U315 is here. So this one is basically means now I'm driving that one. So that multiplexer controls this anode. And after that, they have an individual cathode. So the individual cathode is to control the segments. Because they are each a digit you can see they are about one, two, three, four, five, six, seven. Seven segments here. So they have an use they use another IC to generate the minus 100 volt. Okay. So for the RS sections like this to me is is quite complicated. Okay. So I'm not an RF engineer but I'll try my best to explain what I can understand so far based on what the Mediton's manual says. So for the top right, this is the receiver portion. Then the bottom one, this is the transmitter and multiplexer section. So a multiplexer means that this allows the transmitter and receiver to both use the antenna at the same time while ensuring that their frequencies are isolated for each other. Of course, this can only work if the frequencies are significantly different for each other. But this is guaranteed because the system says that the transmit and receive frequency are exactly 63 mhz. Okay. So this is what the what the professional block diagram I got from the from the Mediton's manual. So let's first start with the off on the left. So the C is the frequency selected from the the micro from the from the pilot right so that input goes to the microcontroller and the microcontroller controls an RF synthesizer. So this is you can take of it as a C it sets the frequency half half the transmitter frequency 520.5 to 575 over here. Okay. Then after that it goes through a series of amplifiers. So there's a continuous wave amplifier and a final pause amplifier. So continuous wave is always on final pause and prior means that is it always on at certain intervals. You can take something as like PWM it only on at certain time. And then you send it over the transmitter section. Then since that they only city size half the frequency there's actually a frequency double low to bring this up to the actual interrogation frequency. Then they amplify and they send it out to the time mixer. We should then send it to the antenna. Okay. So with that I actually cross reference the bomb this schematic and to find out why where are these components are. So this is the buffer the continuous wave amplifiers the pause amplifiers the frequency double low final amplifier and then the time mixer. So that's for the transmit section. Okay. So what about the receive section so the receive section is a bit more complicated. So you can they actually divided into two main parts. First is a signal conditioning stage. And then the second part is what I will call the post signal conditioning stage. Okay. So the first part the signal comes from the antenna to the time mixer and then goes to the band pass filter. Okay. So the band pass filter is basically to filter out whatever that is not desired. Then there's a first stage as amplifier right to bring up the frequency to something that can be can be processed. And then they have something called a mixer here. So the thing about this mixer right is actually try to get the objecting of this mixer is to try to get a 63 mh signal out of that because so that is easier for the subsequent circuitry the process. So how does it work right is that they use a principle called the hetroditing. So they actually have hetroditing basically means to mix two signals and then you'll get another two more signals out of that. So they mix the first one is the receive frequency goes in. Another one is the transmit frequency. So hetroditing you will get actually two one of them is a sum and one of them is a difference. So the objective is we want to get a difference. And since the transmit a frequency and the receive frequencies are guaranteed to 63 mh but we can use that property. So once up once it comes out of the mixer we'll have two signals right. So then here is where we have an inductor use a ESL low impedance of 63 mh. So it basically means filters everything asset for 63 mh. Okay so what about others? So let me briefly go through what are the components where are the components first? So they have much of amplifiers that there's something called a video detector another amplifier and there's a logic driver. Okay and there's something called the automatic gain control. So with that I will go through what are those about. So for the video detector section here so the the purpose of this is to detect the 3.5 per microsecond pulse pair. Right so the 3.5 microsecond pulse pair was is actually this they're trying to detect this particular one. Okay Okay that after that they need to amplify the signal then they need to come to convert it to logic level because this data decoder here right this is actually a normal IC so they need to make sure that is amplified to the correct level that this decoder can actually use. Then they also have means to actually influence the amplification here because sometimes the amplitude can vary greatly and so they need a way to influence it the decoder has a way to influence it and then this sector has also a way to influence it. So they actually affect this amplifier to adjust so they automatically adjust how much amplification they will do to ensure that the signal here comes up at an appropriate level. Okay so that that's quite a lot so this is I have three three major thoughts for my conclusion lah like so they they apparently has a lot talk where to be so DME infrastructure is actually pretty old is actually I will remember right it's about 50 years more than 50 years old already so they actually put a lot top into the frequency selection so that the device on the device side right is easier for the it to process then RF engineering is a very complex thing I think I just barely scratch the surface of what this device can do and it's about and then the last thing is that I'm I'm actually impressed lah basically that engineers at that time in the 1970s they can do something so complex as this yeah so yeah yeah that's that's the end of for him presentation right thank you King Ming I don't know for plus okay anybody have questions for him not a question just a comment it's actually on this slide the the reason it's called video okay yeah is tied up with the bandwidth for quiet so the if you've got a a detector or an amplifier that's only happened to deal with a voice channel that's three kilohertz or maybe 15 kilohertz wide then you can use much simple circuitry but because you're having to perform fairly precise phase measurements on the transmitted and received pulses you can't afford to have a narrow bandwidth component making the edges of the pulse soggy and so you need a high bandwidth detector or amplifier to correctly process the pulse as received before you can perform the the comparison or what you sent and so that that's the reason for needing a wideband amplifier or what is to this day is still called the video amplifier it just just means an amplifier detector with much more bandwidth typically two megahertz than you'd normally use for narrowband audio okay yeah and to the end please wait any well if there's no questions let's thank Kang Meng for putting this presentation in less than a week actually so thank you Kang Meng so i think that brings us to the end of heckware if there's presentations if there's anyone who wants to bring out anything you may do so now but otherwise please feel free to stay and at work and yalah chat with each other i think will keep this this zoom chat open zoom meeting open and if you guys wish to present in next heckware i believe we're gonna have it next month do PMS thank you very much for your for attending and i hope everybody stay safe