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In a radio receiver, a bandspread control is a secondary tuning control that allows accurate tuning of closely spaced frequencies of a radio band. [1] With a main tuning control that covered a wide range of frequencies, for example 10-14 megahertz in a few turns of the tuning knob, a very small motion might change the tuning by tens of kilohertz and would make accurate tuning to any particular frequency difficult. A calibrated bandspread tuning control allows the main tuning to be set to a predefined spot on the control, and the bandspread allows tuning of a particular frequency within some restricted range of the main tuning control. One method of adding a bandspread control was to put a relatively small value variable tuning capacitor and dial directly in parallel with the main tuning variable capacitor ( or connected to a tap on the coil of the tuned circuit). The smaller capacitor would have much less effect on the resonant frequency than the main capacitor, allowing fine di

Schematic of an AGC used in the analog telephone network; the feedback from output level to gain is effected via a Vactrol resistive opto-isolator. Automatic gain control ( AGC ), also called automatic volume control ( AVC ), is a closed-loop feedback regulating circuit in an amplifier or chain of amplifiers, the purpose of which is to maintain a suitable signal amplitude at its output, despite variation of the signal amplitude at the input. The average or peak output signal level is used to dynamically adjust the gain of the amplifiers, enabling the circuit to work satisfactorily with a greater range of input signal levels. It is used in most radio receivers to equalize the average volume (loudness) of different radio stations due to differences in received signal strength, as well as variations in a single station's radio signal due to fading. Without AGC the sound emitted from an AM radio receiver would vary to an extreme extent from a weak to a strong signal; the

Not to be confused with Field strength meter, nor with S-units used in mathematics. S-Meter of a Ten-Tec Orion amateur radio transceiver. An S meter (signal strength meter) is an indicator often provided on communications receivers, such as amateur radio receivers or shortwave broadcast receivers. The scale markings are derived from a system of reporting signal strength from S1 to S9 as part of the R-S-T system. The term S unit can be used to refer to the amount of signal strength required to move an S meter indication from one marking to the next. Contents 1 Technical description 2 IARU Region 1 Technical Recommendation R.1 3 Examples 4 Accuracy 5 See also 6 References 7 Further reading 8 External links Technical description Analogue S meters are actually sensitive microammeters, with a full scale deflection of 50 to 100 μA. In AM receivers, the S meter can be connected to the main detector or use a separate detector at the

This article is about signal processing. For the album by Bill Evans and Jim Hall, see Intermodulation (album). It has been suggested that IMD3 be merged into this article. (Discuss) Proposed since January 2019. A frequency spectrum plot showing intermodulation between two injected signals at 270 and 275 MHz (the large spikes). Visible intermodulation products are seen as small spurs at 280 MHz and 265 MHz. 3rd order active intermodulation animation showing the rapid growth of 3rd order intermodulation products as the power level of 2 CW tones is successively increased at the input of an amplifier operated into its nonlinear region. Fifth, seventh, and ninth order intermodulation products, normally below the noise floor, become visible when the amplifier is overdriven. Intermodulation ( IM ) or intermodulation distortion ( IMD ) is the amplitude modulation of signals containing two or more different frequencies, caused by nonlinearities or time variance in a system

本條目 需要擴充。 ( 2010年7月2日 ) 请協助改善这篇條目，更進一步的信息可能會在討論頁或扩充请求中找到。请在擴充條目後將此模板移除。 阿姆斯特朗砲 或 阿姆斯壯大砲 ，阿姆斯特朗線膛後裝砲〔Armstrong's Rifled Breech Loader〕，是出現在19世紀中期的 後膛 （ 英语 ： Breech-loading weapon ） 火砲，該大砲特點是，從火砲後方裝彈、大砲管內有膛線、使用砲彈為圓筒狀而非圓球狀，此三項特點一直延用至今。由英國律師威廉·阿姆斯特朗（ 英语： William Armstrong ）在1854年發明了這項武器 [1] 。在1858年開始被英軍裝備，隨後在後來的第二次鴉片戰爭中，英軍利用它迅速攻下大沽砲台。 英國皇家海軍戰艦勇士號（HMS Warrior）所裝備的7吋（178 mm）阿姆斯特朗砲 億載金城設置的阿姆斯特朗大砲（仿製品） Fibreglass replica of 7-inch 110lb Armstrong gun on HMS Warrior 目录 1 實際運用 2 參考文獻 3 參見 4 外部連結 實際運用 1874年牡丹社事件爆發後，清朝欽差大臣沈葆楨在今日台南市安平區建立億載金城，並設置了三門英國製阿姆斯特朗砲，口徑為十英吋（254mm）；而現存於億載金城的火砲都是複製品。 Aufbau eines Armstrong-Rohres, 12 pdr 8 cwt Screw breech system of 7-inch Armstrong gun Powder cartridge with lubricator Granate für Vorderlader Armstrong Kanone Malta (Seitenansicht) – alte Lackierung Rückansicht Malta