Sexy Developer

수신단이 IF 트랜스포머에 의한 주파수 낮춤을 하지 않고 송신단이 체배기등을 사용하지 않는지는 실물을 뜯어 보지 못했고, 웹사이트에서도 회로도를 제공하지 않아서 알수는 없지만 어쨌던 PC 용 소프트웨어와 DSP (디지탈 신호 처리 칩) 로 구성되어 실제 운용이 가능한 SDR (Software Difined Radio) 무전기이다. 위에 말...

새로 영입한 녀석인데, AVR 의 ATmega8515 와 인텔 8051 호환의 AT89S52 를 보드 한개에서 시험해 볼수 있는 마시테크 ( http://www.masitech.co.kr ) 사의 제품.   왜나라 야에스의 단파 라디오를 적외선 리모콘으로 조정하기 위한 어플리케이션을 만들기 위해 이것 저것 테스트를 해보려고 구입했다. 어쨌던 새로운 친구의 등장으로 우...

어제는 저번주에 신청한 미해군 전자 기술 독학 교습서 (?) 쯤으로 해석되는 CD-ROM 으로 된 E-Book 이 도착했다. 특급항공우편은 언제나 딱 1주일이면 오는군.   내용은 아래와 같다. 어떤가, 재미날거 같지 않은가? --; 모든 내용은 웹사이트에서 볼 수 있다... 근데 왜 샀냐고? 뭐 여러가지 이유가... ^^;   Naval Electrical Engineering Training Series CD ROM $19.95 (항공...

현충일 밤, 나의 Primary Radio 인 FT-857D 가 개조를 위해 배를 갈랐다. 배를 가른 후 작업전 모습이다. 근데 공구가 고장나서 아직 수술이 안 끝났다. 불쌍한넘. --;

SINGLE-SIDEBAND   You know from studying the single-sideband transmitter material in this chapter you may transmit only one sideband of an AM signal and retain the information transmitted. Now you will see how a single-sideband signal is received.   Advantages   Figure 2-11 illustrates the transmitted signal for both AM and ssb. Ssb communications has several advantages. When you eliminate the carrier and one sideband, all of the transmitted power is concentrated in the other sideband. Also, an ssb signal occupies a smaller portion of the frequency spectrum in comparison to the AM signal. This gives us two advantages, narrower receiver bandpass and the ability to place more signals in a small portion of the frequency spectrum.   Figure 2-11.—Comparison of AM and SSB transmitted signals.   SSB communications systems have some drawbacks. The process of producing an ssb signal is somewhat more complicated than simple amplitude modulation, and frequency stabil...

  Synchronous demodulation / detection ! Today's radio receivers offer very high levels of performance and boast many facilities. Many radio receivers incorporate memories, phase locked loops, direct digital synthesis, digital signal processing and much more. One facility that can be very useful on the short wave bands is synchronous detection or synchronous demodulation as this can give much improved performance for receiving amplitude modulation (AM) transmissions. Unfortunately little is written about this form of modulation, and often it is a matter of accepting that it must be better than any normal options because it is included as a feature in the receiver specification. ! Synchronous detection is used for the detection or demodulation of amplitude modulation (AM). This form of modulation is still widely used for broadcasting on the long, medium and short wave bands despite the fact that there are more efficient forms of modulation that can be used today. The main reason for...

  Synchronous Vs Envelope Detection Updated 10/05/01 Some demodulators provide a choice between envelope and synchronous detection modes. When running the FCC Proof of Performance tests, its important to use the proper detection mode. Especially when measuring differential phase. Let's take a look at the two modes and see what they have to offer. Envelope Detectors Envelope detectors are usually considered to be the simplest form of detector. In fact, they can be quite complicated or they can be as simple as a diode and a low-pass filter. The performance of an envelope detector, when used to demodulate a television signal, is limited by the relative amplitudes of the signal being demodulated (bigger is better), and an effect called quadrature distortion. Quadrature distortion is a result of the asymmetry of our television signal. It's vestigial sideband coming from the modulator or transmitter and nearly single sideband within the television's IF circuit. One nice thing abo...

제 4 장 단측대역 통신   HONGIK UNIVERSITY Telematique Lab. 4-1 단측대역 특성 전력 분배(Power Distribution) 피크 포락선 전력(Peak Envelope Power) : 단측파대 송신기의 출력 전력을 재는 데 사용된 수단. 측대역 전송의 형태(Types of Sideband Transmission) 지시 반송파(Pilot Carrier) : SSB에서 억압 반송파, 반송파는 낮은 레벨로 감소되나 완전히 제거되지는 않는다. 쌍측대역 억제 반송파(Twin-Sideband Suppressed C...

반송파 및 한쪽의 측파대를 제거하고 단일측파대만 사용하여 신호파를 전송하는 방식.   단측파대전송은 SSB(single side band)전송방식이라고도 한다. 진폭변조(振幅變調)된 신호파를 반송파(搬送波)로 변조시키면 피변조파(被變調波)의 스펙트럼은 반송주파수를 대칭축으로 2개의 상 ·하측파대(上下側波帶)가 된...

Beat-Frequency Oscillator   The beat-frequency oscillator (bfo) is necessary when you want to receive cw signals. Cw signals are not modulated with an audio component, you remember, so we must provide one. The action of the rf amplifier, mixer, local oscillator, and IF amplifier is the same for both cw and AM; but the cw signal reaches the detector as a single frequency signal with no sideband components. To produce an af output, you must heterodyne (beat) any cw signal with an rf signal of the proper frequency. This separate signal is obtained from an oscillator known as a beat-frequency oscillator.   Figure 2-20 is a block diagram of a superheterodyne receiver capable of receiving and demodulating a cw signal. The bfo heterodynes at the detector and produces an af output. The detector (second detector) is used primarily because the mixer (first detector) is normally used as the source of agc. Figure 2-20.—Placement of the beat frequency oscillator. If the intermediate ...

주파수의 차가 근소한 2개의 파동이 간섭을 일으켜, 두 주파수의 차에 따라서 진폭이 주기적으로 변하는 합성파(合成波)가 이루는 현상.   이를테면 동시에 전해 오는 두 음이 규칙적으로 강해졌다 약해졌다 하는 현상을 말한다. 두 파동체뿐만 아니라 한 파동체에서도 진동수가 부분적으로 다를 때에는 ...

헤테로다인 [ heterodyne ] - 네이버 용어사전 매스컴용어   다른 힘 또는 두 가지 힘의 조합이라는 뜻. 두 개의 또 다른 주파수를 만들어 내기 위해 두 개의 다른 주파수를 결합시킴. 라디오 수신에 중요한 개선이 있게 만든 기술로 페센덴(Reginald Fessenden)에 의해 발견되었다. 비트(beat)라고도 불린다. 무선공학에서는 두 진동 전류...

Ham Radio BFO Ham Radio (amateur radio) is a popular hobby amongst electronics enthusiasts all over the world. Basically the hobby involves a person in making his own gear consisting of a receiver and transmitter or a transceiver (a receiver and a transmitter in one unit) after procuring a licence from the Ministry of Communications. Home brewing or self construction, an integral part of the hobby, has been sadly neglected in our country, despite the fact that various institutions with governmental help have come into being recently.   Hams aboard can buy the latest transceiver off the shelf at a reasonable price and go on the air immediately. But in India, with a sixty per cent duty involved (now changed?), a commercial transceiver would cost a whopping Rs: 50,000. Hence, it is beyond the reach of an average Indian Ham.   The Indian ham is often handicapped for want of ham gear. To overcome this shortcoming a small receiver and a transmitter can be home brewed with indigenous...

출처: http://www.tpub.com/content/neets/14184/css/14184_157.htm   REGENERATIVE DETECTOR   A simple, one-transistor REGENERATIVE DETECTOR circuit that uses the heterodyning principle for cw operation is shown in figure 3-4. The circuit can be made to oscillate by increasing the amount of energy fed back to the tank circuit from the collector-output circuit (by physically moving tickler coil L2 closer to L1 using the regeneration control). This feedback overcomes losses in the base-input circuit and causes self-oscillations which are controlled by tuning capacitor C1. The received signal from the antenna and the oscillating frequency are both present at the base of transistor Q1. These two frequencies are heterodyned by the nonlinearity of the transistor. The resulting beat frequencies are then rectified by the emitter-base junction and produce a beat note which is amplified in the collector-output circuit. The af currents in the collector circuit actuate the phones....

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