Further improvement of explanations
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+133
-133
@@ -1024,8 +1024,8 @@
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"confidence": 8
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},
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"AD218": {
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"revision": 2,
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"explanation": "Moving the potentiometer toward X raises the reverse voltage on the varicap; higher reverse voltage lowers its capacitance, so the LC resonant frequency rises.",
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"revision": 3,
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"explanation": "Follow the DC control voltage from the potentiometer to the varicap. Moving the wiper toward X increases the diode's reverse bias; a more strongly reverse-biased junction has less capacitance. Because that varicap is part of the LC resonator, reducing $C$ raises $f_0=1/(2\\pi\\sqrt{LC})$, so the oscillator frequency increases.",
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"source": "https://50ohm.de/NEA_oszillator_vco.html#AD218",
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"confidence": 7
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},
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@@ -1080,14 +1080,14 @@
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"confidence": 8
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},
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"AD227": {
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"revision": 2,
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"explanation": "Looser coupling gives a narrower, lower transfer curve; in the shown family, curve c is less coupled than curve a.",
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"revision": 3,
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"explanation": "The two LC sections are separate resonators coupled by their magnetic fields. Weaker coupling transfers less energy and produces a lower, narrower single response peak; stronger coupling broadens the response and eventually splits it into two peaks. Reading the plotted family with that progression shows that curve c is less strongly coupled than curve a.",
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"source": "https://50ohm.de/NEA_schwingkreis_2.html#AD227",
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"confidence": 7
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},
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"AD228": {
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"revision": 2,
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"explanation": "Critical coupling gives the flattest single peak at maximum useful width, while overcritical coupling creates the double-humped response; those are curves b and a respectively.",
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"revision": 3,
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"explanation": "Increase the magnetic coupling between the two tuned circuits mentally. At critical coupling the response has reached its greatest useful width while remaining a single flat-topped peak; with still more coupling, the two resonant modes separate into a double hump. In the drawing those signatures are curve b for critical coupling and curve a for overcoupling.",
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"source": "https://50ohm.de/NEA_schwingkreis_2.html#AD228",
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"confidence": 7
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},
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@@ -1186,8 +1186,8 @@
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"confidence": 8
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},
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"AD314": {
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"revision": 2,
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"explanation": "A mains input filter uses a common-mode choke and capacitors to keep switching interference from being conducted back into the power network.",
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"revision": 3,
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"explanation": "Trace the 50 Hz mains path first: line and neutral must pass through the two coupled choke windings without being connected to protective earth, so normal load current is delivered. For high-frequency switching noise, the choke has high impedance and the capacitors provide short return paths across line/neutral or to earth. The correct drawing therefore combines that common-mode choke and safety capacitors as a low-pass mains filter, preventing RF noise from travelling back onto the supply cable.",
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"source": "https://50ohm.de/NEA_schaltnetzteil_2.html#AD314",
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"confidence": 7
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},
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@@ -1247,44 +1247,44 @@
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"confidence": 8
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},
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"AD323": {
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"revision": 2,
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"explanation": "The circuit combines a DC feed path through an inductor with an RF path through a coupling capacitor, which is the structure of a Bias-T.",
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"revision": 3,
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"explanation": "Trace DC and RF as though they were two different currents. DC reaches the combined port through the inductor but cannot pass the series capacitor; RF reaches the combined port through the capacitor but sees the inductor as a high impedance. A network that combines and separates the two on one cable is a Bias-T.",
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"source": "https://50ohm.de/NEA_fernspeiseweiche.html#AD323",
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"confidence": 7
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},
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"AD324": {
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"revision": 2,
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"explanation": "C1 is the RF coupling capacitor toward the receiver; it passes RF but blocks the DC supply from reaching the receiver input.",
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"revision": 3,
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"explanation": "$C_1$ lies in series between the RF receiver port and the combined RF/DC port. Its reactance is low at the wanted RF frequency, so the received signal passes, but steady supply voltage cannot cross it. It is therefore the RF coupling and DC-blocking capacitor that protects the receiver input.",
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"source": "https://50ohm.de/NEA_fernspeiseweiche.html#AD324",
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"confidence": 7
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},
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"AD325": {
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"revision": 2,
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"explanation": "The Bias-T inductor is in the DC feed path, so it must safely carry the supply current for the remote device.",
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"revision": 3,
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"explanation": "The coil is the only DC path from the supply to the remote device, so its wire must carry the full operating current without overheating or saturating its core. At the same time its inductive reactance must be high enough at the lowest RF frequency to keep RF out of the supply port. Both current rating and RF impedance matter when dimensioning it.",
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"source": "https://50ohm.de/NEA_fernspeiseweiche.html#AD325",
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"confidence": 7
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},
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"AD401": {
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"revision": 2,
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"explanation": "The collector is the AC-common terminal and the output is taken from the emitter, so this is the collector configuration, also called an emitter follower.",
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"revision": 3,
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"explanation": "Trace the signal terminals before naming the stage: the input drives the base, the output is taken from the emitter, and the collector is tied to the supply, which is an AC-common point. The shared collector identifies a common-collector stage, also called an emitter follower.",
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"source": "https://50ohm.de/NEA_kollektorschaltung.html#AD401",
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"confidence": 7
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},
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"AD402": {
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"revision": 2,
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"explanation": "An emitter follower has voltage gain just below unity because the emitter follows the base voltage, and it is non-inverting, so the phase shift is 0 degrees.",
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"revision": 3,
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"explanation": "The base is the input and the emitter is the output. When the base voltage rises, the emitter rises with it while remaining about one base-emitter drop lower, so there is no inversion: $\\varphi=0^\\circ$. Emitter feedback keeps the voltage gain slightly below one, typically about 0.9 to 0.98.",
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"source": "https://50ohm.de/NEA_kollektorschaltung.html#AD402",
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"confidence": 7
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},
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"AD403": {
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"revision": 2,
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"explanation": "A collector configuration buffers a high-impedance source into a low-impedance load; its current gain is useful even though voltage gain is below one.",
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"revision": 3,
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"explanation": "At the input, the base draws only the small base current, so the source sees a high impedance. At the output, a load-current change is supplied through the transistor and corrected by emitter feedback, so the emitter behaves like a low-impedance source. The stage therefore transforms high input impedance into much lower output impedance.",
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"source": "https://50ohm.de/NEA_kollektorschaltung.html#AD403",
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"confidence": 7
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},
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"AD404": {
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"revision": 2,
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"explanation": "Because it has high input impedance and low output impedance, an emitter follower can isolate an oscillator from changing load impedance.",
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"revision": 3,
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"explanation": "An oscillator should not be pulled when its load changes. The emitter follower's base presents a high impedance to the oscillator, while its emitter supplies the load from a low impedance with nearly unity voltage gain. It therefore works as a buffer between oscillator and load.",
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"source": "https://50ohm.de/NEA_kollektorschaltung.html#AD404",
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"confidence": 7
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},
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@@ -1295,8 +1295,8 @@
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"confidence": 8
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},
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"AD406": {
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"revision": 2,
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"explanation": "Without DC bias the transistor conducts only when the base-emitter voltage exceeds about 0.6 V; the collector voltage then dips, so the output is a clipped, inverted pulse-like waveform.",
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"revision": 3,
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"explanation": "This is an unbiased common-emitter stage: the input reaches the base, the emitter is the common reference, and the output is taken at the collector. Only input portions above roughly the silicon base-emitter threshold make the transistor conduct. Collector current then increases the drop across the collector resistor, pulling the collector output downward, so the possible output is clipped and inverted.",
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"source": "https://50ohm.de/NEA_emitterschaltung.html#AD406",
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"confidence": 7
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},
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@@ -1307,52 +1307,52 @@
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"confidence": 8
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},
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"AD408": {
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"revision": 2,
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"explanation": "The emitter-stage output is taken at the collector, so the collector waveform is inverted relative to the input while the bias and coupling points keep their shown DC roles.",
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"revision": 3,
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"explanation": "First separate DC levels from signal phase. The base waveform follows the applied input, and the emitter follows the base without inversion. A rising base/emitter voltage increases collector current; the larger drop across the collector resistor makes the collector voltage fall. Thus the emitter is in phase with the input while the collector output is $180^\\circ$ out of phase.",
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"source": "https://50ohm.de/NEA_emitterschaltung.html#AD408",
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"confidence": 7
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},
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"AD409": {
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"revision": 2,
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"explanation": "The emitter is the common reference for input and output, with the output taken at the collector through a coupling capacitor, which identifies an emitter configuration.",
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"revision": 3,
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"explanation": "Locate the three signal references: the input is applied between base and emitter, the output is taken between collector and emitter, and the emitter is shared by both. That shared terminal gives the topology its name: a common-emitter amplifier.",
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"source": "https://50ohm.de/NEA_emitterschaltung.html#AD409",
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"confidence": 7
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},
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"AD410": {
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"revision": 2,
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"explanation": "A bypassed emitter stage can provide large voltage gain, and the collector output is inverted relative to the base input, so the phase shift is 180 degrees.",
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"revision": 3,
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"explanation": "The bypass capacitor makes the emitter approximately AC-ground, so emitter feedback is small and the collector resistor can produce a large voltage swing—typically a gain magnitude of 100 to 300. More base voltage means more collector current and therefore less collector voltage, so the output is inverted and $\\varphi=180^\\circ$.",
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"source": "https://50ohm.de/NEA_emitterschaltung.html#AD410",
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"confidence": 7
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},
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"AD411": {
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"revision": 2,
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"explanation": "R1 and R2 form a voltage divider feeding the base, setting the transistor's DC bias point before the AC signal is applied.",
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"revision": 3,
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"explanation": "$R_1$ connects the base node toward the positive supply and $R_2$ connects it toward the return rail. Together they form a voltage divider that fixes the base's DC voltage before any AC input arrives. That base voltage, minus the base-emitter drop, establishes the emitter current and hence the transistor's quiescent operating point.",
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"source": "https://50ohm.de/NEA_emitterschaltung.html#AD411",
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"confidence": 7
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},
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"AD412": {
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"revision": 2,
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"explanation": "The coupling capacitors pass the AC signal into and out of the stage while blocking the DC bias voltages from adjacent circuits.",
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"revision": 3,
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"explanation": "The transistor stage needs its own DC base and collector voltages, but the source and following stage must not disturb them. The input capacitor passes the changing signal into the base while blocking DC; the output capacitor does the same from the collector to the load. They therefore provide AC coupling together with DC isolation.",
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"source": "https://50ohm.de/NEA_emitterschaltung.html#AD412",
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"confidence": 7
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},
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"AD413": {
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"revision": 2,
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"explanation": "The emitter bypass capacitor shorts the emitter resistor for AC, reducing emitter degeneration and therefore maximizing AC voltage gain.",
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"revision": 3,
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"explanation": "The emitter resistor stabilises the DC operating point, but for AC it would also create negative feedback: more emitter current raises emitter voltage and reduces the base-emitter change. $C_1$ provides a low-reactance path around that resistor for the signal while leaving the DC path unchanged. Removing the AC feedback maximises voltage gain.",
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"source": "https://50ohm.de/NEA_emitterschaltung.html#AD413",
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"confidence": 7
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},
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"AD414": {
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"revision": 2,
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"explanation": "Removing the emitter bypass capacitor leaves the emitter resistor active for AC feedback, so emitter degeneration lowers the voltage gain.",
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"revision": 3,
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"explanation": "With $C_1$ present, AC emitter current bypasses the emitter resistor and the emitter stays near AC-ground. Removing $C_1$ forces the signal current through the resistor: the resulting emitter-voltage change opposes the base-emitter input change. This emitter degeneration is negative feedback, so the voltage gain decreases rather than falling to zero.",
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"source": "https://50ohm.de/NEA_emitterschaltung.html#AD414",
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"confidence": 7
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},
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"AD415": {
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"revision": 2,
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"explanation": "With no emitter bypass capacitor, the emitter resistor provides negative feedback and the stage gain drops from a large value to roughly the resistor-ratio value, about 10 here.",
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"revision": 3,
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"explanation": "Read the schematic in two layers. For DC, the $220\\,\\text{k}\\Omega$ and $22\\,\\text{k}\\Omega$ resistors bias the base, the $2.2\\,\\text{k}\\Omega$ emitter resistor stabilises the operating point, and the input/output capacitors keep those DC voltages inside the stage. For AC, the emitter capacitor is absent, so the emitter resistor is no longer bypassed: a rising emitter current raises the emitter voltage and opposes the original base-emitter change (negative feedback). The approximate common-emitter voltage-gain magnitude is therefore set by the resistor ratio, $|v_U| \\approx R_C/R_E = 22\\,\\text{k}\\Omega / 2.2\\,\\text{k}\\Omega = 10$. The collector signal is still inverted, but the question asks only for the gain magnitude.",
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"source": "https://50ohm.de/NEA_emitterschaltung.html#AD415",
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"confidence": 7
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"confidence": 8
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},
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"AD416": {
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"revision": 2,
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@@ -1463,14 +1463,14 @@
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"confidence": 7
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},
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"AD501": {
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"revision": 2,
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"explanation": "A diode followed by an RC load recovers the envelope of an AM signal, so the circuit is an envelope demodulator for AM.",
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"revision": 3,
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"explanation": "The AM IF signal first reaches the diode, which conducts on one RF polarity and turns the symmetrical carrier into pulses whose peaks follow the modulation envelope. The following resistor-capacitor network removes the RF cycles while retaining the slower audio variation. A diode followed by that RC load is an AM envelope detector.",
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"source": "https://50ohm.de/NEA_demodulator.html#AD501",
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"confidence": 7
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},
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"AD502": {
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"revision": 2,
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"explanation": "At point X the diode has rectified the AM IF waveform but the RC network has not yet fully smoothed it, so the signal follows the positive envelope with RF ripple remaining.",
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"revision": 3,
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"explanation": "At X the diode has already removed one polarity of the AM IF, but the following smoothing has not yet eliminated the carrier-frequency variation. The voltage therefore consists of positive RF peaks whose outline follows the audio envelope. Choose the waveform showing a rectified envelope with RF ripple, not clean audio or the original symmetrical carrier.",
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"source": "https://50ohm.de/NEA_demodulator.html#AD502",
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"confidence": 7
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},
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@@ -1482,32 +1482,32 @@
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"provenance": "50ohm-loesungsweg"
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},
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"AD504": {
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"revision": 3,
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"explanation": "A tuned circuit offset from the IF converts FM frequency deviation, German Hub/Frequenzhub, into amplitude changes. A diode detector can then recover those amplitude changes as audio; that method is a slope discriminator.",
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"revision": 4,
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"explanation": "The tuned circuit is deliberately set on a slope rather than at the centre of resonance. As the FM input moves up and down in frequency, that slope converts frequency deviation into corresponding amplitude changes. The diode then rectifies those amplitude changes and the RC network recovers the audio, which identifies a slope discriminator.",
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"source": "https://50ohm.de/NEA_demodulator.html#AD504",
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"confidence": 7
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},
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"AD505": {
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"revision": 2,
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"explanation": "A PLL can follow the frequency of an FM signal; the VCO control voltage is then proportional to the original modulation, so the block is a PLL FM demodulator.",
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"revision": 3,
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"explanation": "The phase detector compares the incoming FM signal with the VCO output, and the loop filter drives the VCO until the loop tracks the input frequency. Whenever the input frequency deviates, the required VCO control voltage moves with it. That control voltage reproduces the modulation, so the loop is a PLL FM demodulator.",
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"source": "https://50ohm.de/NEA_demodulator.html#AD505",
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"confidence": 7
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},
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"AD506": {
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"revision": 2,
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"explanation": "A product detector mixes the SSB signal with a locally regenerated carrier/BFO so the sideband is converted back to audio.",
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"revision": 3,
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"explanation": "An SSB signal has no carrier available for an ordinary envelope detector. The circuit therefore feeds the SSB IF and a locally regenerated BFO carrier into the nonlinear detector; their difference products fall in the audio range and the low-pass output retains them. Multiplying those two inputs makes the stage a product detector.",
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"source": "https://50ohm.de/NEA_demodulator.html#AD506",
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"confidence": 7
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},
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"AD507": {
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"revision": 2,
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"explanation": "The circuit varies the RF carrier amplitude in step with the audio signal, which is the defining operation of an AM modulator.",
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"revision": 3,
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"explanation": "Follow the two inputs to the nonlinear element: one is the RF carrier and the other is the audio signal. The audio changes the carrier path's gain, so the RF amplitude rises and falls with the instantaneous audio voltage while the carrier frequency stays fixed. That operation is amplitude modulation.",
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"source": "https://50ohm.de/NEA_modulatoren.html#AD507",
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"confidence": 7
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},
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"AD508": {
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"revision": 2,
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"explanation": "The audio voltage drives a varicap in the oscillator tank circuit; changing capacitance changes oscillator frequency, so the generated signal is FM.",
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"revision": 3,
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"explanation": "The diode is reverse biased and sits inside the oscillator's LC frequency-determining network, so it acts as a varicap rather than a rectifier. Audio voltage changes its junction capacitance, which moves the resonant frequency above and below the centre frequency. The generated carrier is therefore frequency modulated.",
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"source": "https://50ohm.de/NEA_modulatoren.html#AD508",
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"confidence": 7
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},
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@@ -1602,44 +1602,44 @@
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"confidence": 8
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},
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"AD614": {
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"revision": 2,
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"explanation": "The LC resonator and capacitive divider form a Colpitts-style three-point oscillator, with the capacitive divider providing the feedback path.",
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"revision": 3,
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"explanation": "The transistor supplies gain, while the LC resonator selects the oscillation frequency. Two capacitors form a divider that returns a controlled fraction of the output with the phase needed for positive feedback. That three-point capacitive feedback network identifies a Colpitts-type oscillator.",
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"source": "https://50ohm.de/NEA_oszillator_schaltungen.html#AD614",
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"confidence": 7
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},
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"AD615": {
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"revision": 2,
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"explanation": "The output should be taken at the low-impedance buffered point so the load disturbs the resonant circuit as little as possible; in the drawing that is point D.",
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"revision": 3,
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"explanation": "Do not take power directly from the resonator: an external load there would add resistance and capacitance, changing frequency and possibly stopping oscillation. Point D is the low-impedance buffered node after the active device, so it can drive a following stage while disturbing the resonant loop least. The RF output should be coupled from D.",
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"source": "https://50ohm.de/NEA_oszillator_schaltungen.html#AD615",
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"confidence": 7
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},
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"AD616": {
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"revision": 2,
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"explanation": "C1 and C2 form the capacitive voltage divider of the Colpitts oscillator; a fraction of the output is fed back to sustain oscillation.",
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"revision": 3,
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"explanation": "$C_1$ and $C_2$ are connected as a capacitive divider across the resonant network. Their junction returns only a fraction of the output to the transistor input; the divider polarity supplies the required feedback phase and its ratio sets the feedback amount. They sustain oscillation rather than merely smoothing the supply.",
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"source": "https://50ohm.de/NEA_oszillator_schaltungen.html#AD616",
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"confidence": 7
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},
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"AD617": {
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"revision": 2,
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"explanation": "The transistor is used in collector configuration and the crystal sets the oscillation frequency; this circuit is a capacitively fed crystal oscillator on the crystal's fundamental frequency.",
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"revision": 3,
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"explanation": "The crystal is the sharply selective frequency-determining element, while $C_1$ and $C_2$ provide the capacitive feedback path. The collector is the AC-common terminal and the feedback/output action occurs through the emitter, so the transistor operates in common-collector configuration. With the crystal used at its marked resonance, this is a capacitively fed fundamental crystal oscillator.",
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"source": "https://50ohm.de/NEA_oszillator_schaltungen.html#AD617",
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"confidence": 7
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},
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"AD618": {
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"revision": 2,
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"explanation": "Point 3 is part of the frequency-determining resonant network; probe capacitance loads that point and therefore shifts the oscillator frequency.",
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"revision": 3,
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"explanation": "Point 3 belongs to the crystal/capacitor resonant loop rather than to an isolated output. An oscilloscope or counter probe contributes its own input capacitance in parallel at that node, changing the effective resonant capacitance. The oscillator is therefore pulled and the measured frequency shifts from its undisturbed value.",
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"source": "https://50ohm.de/NEA_oszillator_schaltungen.html#AD618",
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"confidence": 7
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},
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"AD619": {
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"revision": 2,
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"explanation": "The oscillator should be measured at the buffered output point, because probing the resonant circuit directly would add capacitance and detune it; in the drawing that is point 4.",
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"revision": 3,
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"explanation": "Points inside the resonant loop are sensitive to a probe's capacitance and resistance. Point 4 is the buffered, lower-impedance output, so attaching a frequency counter there changes the resonator much less. The oscillator frequency should therefore be measured at point 4.",
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"source": "https://50ohm.de/NEA_oszillator_schaltungen.html#AD619",
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"confidence": 7
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},
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"AD620": {
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"revision": 2,
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"explanation": "The block diagram uses a clock, digital address/phase generation, a sine lookup table, and a D/A converter to synthesize the output, which is direct digital synthesis.",
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"revision": 3,
|
||||
"explanation": "Follow the digital signal path from left to right: the reference clock advances a phase accumulator, its digital phase addresses a sine lookup table, and the D/A converter turns those samples into an analogue waveform. The low-pass filter then removes the sampling images. Because the frequency is created numerically without a feedback loop or VCO, the arrangement is direct digital synthesis (DDS).",
|
||||
"source": "https://50ohm.de/NEA_oszillator_dds.html#AD620",
|
||||
"confidence": 7
|
||||
},
|
||||
@@ -2359,20 +2359,20 @@
|
||||
"confidence": 7
|
||||
},
|
||||
"AF308": {
|
||||
"revision": 2,
|
||||
"explanation": "The balanced diode modulator cancels the carrier and leaves the modulation sidebands, so it generates AM with suppressed carrier.",
|
||||
"revision": 3,
|
||||
"explanation": "On alternate carrier half-cycles, opposite diode pairs conduct and reverse the polarity with which the audio is applied to the RF path. The transformer symmetry makes the unmodulated carrier contributions cancel at the output, while the audio-dependent products remain. The result is double-sideband AM with suppressed carrier.",
|
||||
"source": "https://50ohm.de/NEA_modulatoren.html#AF308",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF309": {
|
||||
"revision": 2,
|
||||
"explanation": "The balancing network trims amplitude and phase so the carrier components cancel as well as possible in the balanced modulator.",
|
||||
"revision": 3,
|
||||
"explanation": "Perfect carrier cancellation requires the two paths through the balanced modulator to have equal amplitude and opposite phase. Component tolerances leave a small residual carrier; $R_1$ trims the balance and $C_1$ corrects the frequency-dependent phase/amplitude error. Together they minimise carrier leakage at the output.",
|
||||
"source": "https://50ohm.de/NEA_modulatoren.html#AF309",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF310": {
|
||||
"revision": 2,
|
||||
"explanation": "The diode is a varicap in the oscillator tank; the audio voltage changes its capacitance, shifting the resonant frequency and producing FM.",
|
||||
"revision": 3,
|
||||
"explanation": "The diode is reverse biased inside the oscillator tank, so it behaves as a voltage-dependent capacitance. Audio applied to it changes the tank's total capacitance and hence its resonant frequency in step with the audio waveform. Its function is therefore to generate FM, not to rectify the signal.",
|
||||
"source": "https://50ohm.de/NEA_modulatoren.html#AF310",
|
||||
"confidence": 7
|
||||
},
|
||||
@@ -2383,8 +2383,8 @@
|
||||
"confidence": 8
|
||||
},
|
||||
"AF312": {
|
||||
"revision": 2,
|
||||
"explanation": "The stage is biased and tuned to use distortion harmonics rather than linear amplification, which identifies it as a frequency multiplier.",
|
||||
"revision": 3,
|
||||
"explanation": "The transistor is driven into a nonlinear region so its collector waveform contains harmonics of the input. The output LC circuit is tuned to one chosen harmonic and rejects the fundamental and the other products. Selecting a multiple of the input frequency makes the stage a frequency multiplier.",
|
||||
"source": "https://50ohm.de/NEA_frequenzvervielfacher_2.html#AF312",
|
||||
"confidence": 7
|
||||
},
|
||||
@@ -2431,116 +2431,116 @@
|
||||
"confidence": 8
|
||||
},
|
||||
"AF406": {
|
||||
"revision": 2,
|
||||
"explanation": "The marked output network is the matching section; it transforms the external load impedance to the impedance the transistor stage needs.",
|
||||
"revision": 3,
|
||||
"explanation": "Start at the transistor output and follow the marked reactive network toward the external load. Its series and shunt reactances change the voltage/current ratio seen by the transistor, so the external load appears as the lower optimum load required by the power device. The marked parts are therefore the output impedance-matching network.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF406",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF407": {
|
||||
"revision": 2,
|
||||
"explanation": "The marked input matching parts transform the previous stage's output impedance to the transistor's required input impedance for proper drive.",
|
||||
"revision": 3,
|
||||
"explanation": "Here the marked components lie before the transistor rather than after it. They transform the driving stage's output impedance to the power transistor's input impedance, allowing RF drive power to reach the device instead of being reflected. They are the input matching network.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF407",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF408": {
|
||||
"revision": 2,
|
||||
"explanation": "The tuned resonant circuits in the RF signal path make the stage frequency-selective, so it is a selective RF amplifier rather than a broadband or audio amplifier.",
|
||||
"revision": 3,
|
||||
"explanation": "The input and output both contain LC resonant circuits. Each presents the desired impedance only around its tuned frequency and rejects signals away from resonance. Those frequency-selective networks identify a tuned, selective RF amplifier rather than a broadband or audio stage.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF408",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF409": {
|
||||
"revision": 2,
|
||||
"explanation": "A tapped resonant circuit can provide impedance transformation, letting the preceding stage drive the tuned amplifier input at a suitable impedance point.",
|
||||
"revision": 3,
|
||||
"explanation": "The entire resonant winding can have a high impedance at resonance, while a tap uses only part of the winding and therefore presents a lower impedance. Connecting the drive at X couples energy into the tuned circuit at a suitable impedance without heavily damping it; the tap provides impedance matching.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF409",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF410": {
|
||||
"revision": 2,
|
||||
"explanation": "C1 and C2 are part of the matching network, setting the impedance transformation between the transistor stage and the connected circuit.",
|
||||
"revision": 3,
|
||||
"explanation": "$C_1$ and $C_2$ are not merely bypass capacitors: they sit in the RF path as a capacitive divider. Their ratio determines how strongly the transistor is coupled to the external circuit and therefore the impedance transformation. Together they form part of the matching network.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF410",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF411": {
|
||||
"revision": 2,
|
||||
"explanation": "The marked supply decoupling path gives RF a low-impedance route to ground, preventing RF from entering the DC supply line.",
|
||||
"revision": 3,
|
||||
"explanation": "The marked branch connects the DC supply rail to RF ground through a bypass capacitor while the series feed element impedes RF. DC can still reach the active device, but RF current is diverted locally instead of travelling along the supply wiring. X is therefore supply decoupling.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF411",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF412": {
|
||||
"revision": 2,
|
||||
"explanation": "The push-pull transformer-coupled layout is intended for broadband RF amplification rather than a narrow tuned stage, so it is a broadband push-pull amplifier.",
|
||||
"revision": 3,
|
||||
"explanation": "The input transformer drives the two transistors in opposite phase, and the output transformer recombines their currents. Transformers rather than narrow LC resonators provide the impedance transformations, so the stage covers a broad frequency range. The topology is a broadband push-pull amplifier.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF412",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF413": {
|
||||
"revision": 2,
|
||||
"explanation": "The two cascaded broadband transformer-coupled stages identify the circuit as a two-stage broadband RF amplifier.",
|
||||
"revision": 3,
|
||||
"explanation": "Read from left to right: one transformer-coupled transistor pair supplies gain, then a second similar stage adds more gain before the output transformer. Because both stages use broadband transformers instead of individually tuned circuits, the drawing is a two-stage broadband RF amplifier.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF413",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF414": {
|
||||
"revision": 2,
|
||||
"explanation": "The transformer couples stages while transforming the output impedance of one emitter stage to the input impedance of the following emitter stage.",
|
||||
"revision": 3,
|
||||
"explanation": "$T_1$ lies between two common-emitter stages. It carries the first stage's RF collector signal to the next base circuit while its turns ratio converts the first stage's output impedance to the following stage's input impedance. It therefore provides both coupling and interstage impedance matching.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF414",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF415": {
|
||||
"revision": 2,
|
||||
"explanation": "Large capacitors are effective at low frequencies but poorer at very high RF; small capacitors keep low impedance at high frequencies, so the parallel pair decouples over a wider range.",
|
||||
"revision": 3,
|
||||
"explanation": "Each capacitor pair bridges the same two nodes, but the values differ because real capacitors cease to be ideal at high frequency. The larger capacitor provides low reactance lower in the RF range; the smaller one has lower stray inductance and remains effective higher up. In parallel they decouple a much wider frequency range.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF415",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF416": {
|
||||
"revision": 2,
|
||||
"explanation": "The resistor damps the transformer winding, reducing excessive Q and helping prevent parasitic oscillations.",
|
||||
"revision": 3,
|
||||
"explanation": "The secondary of $T_2$ and its stray capacitances can form an unwanted high-Q resonator. Placing $R$ across that winding absorbs resonant energy and lowers the Q, flattening the response. This damping helps prevent parasitic oscillation without being the main load-matching element.",
|
||||
"source": "https://50ohm.de/NEA_parasitaere_schwingungen.html#AF416",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF417": {
|
||||
"revision": 2,
|
||||
"explanation": "The transformers provide broadband impedance transformation between the 50 ohm system and the low transistor input and output impedances.",
|
||||
"revision": 3,
|
||||
"explanation": "Power-transistor input and output impedances are much lower than the surrounding 50-ohm system. $T_1$ transforms 50 ohms down for the transistor inputs and $T_2$ transforms the combined low output impedance back up to 50 ohms. Their transformer coupling makes that matching broadband.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF417",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF418": {
|
||||
"revision": 2,
|
||||
"explanation": "An inductor in series with shunt capacitors forms an LC low-pass section: it passes DC/low-frequency supply current but diverts RF to ground.",
|
||||
"revision": 3,
|
||||
"explanation": "Follow DC and RF separately through the supply branch. The series coil passes DC but has increasing RF reactance; $C_2$ and $C_3$ provide low-impedance RF paths to ground over different frequency ranges. Together they form a supply low-pass that prevents RF from entering the DC line.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF418",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF419": {
|
||||
"revision": 2,
|
||||
"explanation": "The choke and bypass capacitors form supply-line filtering, reducing RF components on the DC supply line rather than filtering the transmitted RF path itself.",
|
||||
"revision": 3,
|
||||
"explanation": "The coil is in series with the drain-supply lead, while $C_2$ and $C_3$ shunt that lead to RF ground. DC reaches the amplifier through the coil, but RF is blocked by the coil and bypassed by the capacitors. This cleans the supply lead; it is not the harmonic filter in the transmitted-signal path.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF419",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF420": {
|
||||
"revision": 2,
|
||||
"explanation": "Moving R3 toward position 3 lowers the gate bias for both LDMOS devices in the DC equivalent circuit, so both drain currents decrease.",
|
||||
"revision": 3,
|
||||
"explanation": "For DC, the coupling capacitors are open and the LDMOS gates draw essentially no current, leaving $R_3$ as the shared gate-bias adjustment. Moving its wiper toward position 3 lowers both gate-source voltages. Lower gate bias produces less quiescent drain current in both transistors.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF420",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF421": {
|
||||
"revision": 3,
|
||||
"explanation": "For DC bias, the gates draw negligible current and the resistor network acts as a voltage divider; at stop 1 the divider sets the gate-source voltage to 3.5 V. <u>Hilfsmittel:</u> the FET gate draws negligible current (device knowledge), so the resistor chain is an unloaded voltage divider $U_G = U_B\\cdot R/(\\sum R)$ (Spannungsteiler, S. 12).",
|
||||
"revision": 4,
|
||||
"explanation": "Analyse only the DC network: the RF coupling capacitors are open and the FET gate draws negligible current, so the resistors form an unloaded divider. At stop 1, the divider places the gate $3.5\\,\\text{V}$ above the source. Thus $U_\\mathrm{GS}=3.5\\,\\text{V}$. <u>Hilfsmittel:</u> use the formula sheet's unloaded-divider relation $U_2/U_G = R_2/(R_1+R_2)$ (Spannungsteiler, S.12), with $U_2$ corresponding to $U_\\mathrm{GS}$ here; negligible FET gate current is device knowledge.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF421",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF422": {
|
||||
"revision": 2,
|
||||
"explanation": "The coils are RF chokes in the supply feeds; they pass DC but present high impedance to RF, keeping RF out of the supply line.",
|
||||
"revision": 3,
|
||||
"explanation": "Each X-marked coil is in series between the supply and an LDMOS drain. It must carry the DC drain current, but at RF its inductive reactance is high, so the RF output current is kept in the transformer/load path rather than escaping into the supply. The coils are RF chokes.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF422",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF423": {
|
||||
"revision": 2,
|
||||
"explanation": "Increasing LDMOS quiescent current means raising both gate-bias voltages, so both bias controls are moved toward UBIAS.",
|
||||
"revision": 3,
|
||||
"explanation": "Quiescent current is set by each LDMOS gate's DC bias, not by the RF matching components. Raising a gate toward $U_\\mathrm{BIAS}$ increases its gate-source voltage and drain current. Because both devices' quiescent currents must rise, both bias adjustments are moved toward $U_\\mathrm{BIAS}$.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF423",
|
||||
"confidence": 7
|
||||
},
|
||||
"AF424": {
|
||||
"revision": 2,
|
||||
"explanation": "R4 affects only the bias path for transistor 1 in the shown circuit; moving its wiper toward UBIAS raises that gate bias and drain current, while transistor 2 is unchanged.",
|
||||
"revision": 3,
|
||||
"explanation": "Trace the two DC gate-bias branches independently. $R_4$ is connected only to transistor 1's gate branch, so moving its wiper toward $U_\\mathrm{BIAS}$ raises that gate-source voltage and its drain current. Transistor 2 uses the other bias branch, so its drain current is unchanged.",
|
||||
"source": "https://50ohm.de/NEA_leistungsvertaerker.html#AF424",
|
||||
"confidence": 7
|
||||
},
|
||||
@@ -3444,26 +3444,26 @@
|
||||
"confidence": 8
|
||||
},
|
||||
"AG421": {
|
||||
"revision": 2,
|
||||
"explanation": "A 2:1 turns ratio gives a 4:1 impedance ratio; transforming 50 ohms by 4 gives 200 ohms.",
|
||||
"revision": 3,
|
||||
"explanation": "Count turns from the coax connection to the balanced antenna connection: the two eight-turn sections give a 2:1 turns ratio. Impedance changes by the square of that ratio, so the transformation is $2^2=4$. A $50\\,\\Omega$ coax input therefore corresponds to a $200\\,\\Omega$ balanced antenna.",
|
||||
"source": "https://50ohm.de/NEA_mantelwellen_2.html#AG421",
|
||||
"confidence": 8
|
||||
},
|
||||
"AG422": {
|
||||
"revision": 2,
|
||||
"explanation": "The balun uses the winding ratio to transform the 200 ohm balanced load down by 4:1, so the coax-side impedance is 50 ohms.",
|
||||
"revision": 3,
|
||||
"explanation": "The folded dipole is connected across the full balanced winding, while the coax uses the lower-turn side. The 2:1 turns ratio gives a 4:1 impedance ratio, so the dipole's $200\\,\\Omega$ is seen from the coax side as $200\\,\\Omega/4=50\\,\\Omega$. The centre arrangement also performs the balanced-to-unbalanced conversion.",
|
||||
"source": "https://50ohm.de/NEA_mantelwellen_2.html#AG422",
|
||||
"confidence": 8
|
||||
},
|
||||
"AG423": {
|
||||
"revision": 2,
|
||||
"explanation": "The half-wave bypass line provides both impedance transformation and phase reversal, matching the folded dipole's high balanced impedance to lower unbalanced coax.",
|
||||
"revision": 3,
|
||||
"explanation": "Identify the three parts separately: the folded dipole is a balanced $240\\,\\Omega$ load, the coax is an unbalanced $60\\,\\Omega$ line, and the extra coax path is one half-wavelength long. That detour adds $180^\\circ$, so the two dipole terminals receive equal, opposite-phase voltages while the shield remains at the centre. Each dipole terminal is about $120\\,\\Omega$ to that centre; the two paths appear in parallel at the coax input, giving $60\\,\\Omega$. The overall connection therefore provides the shown 4:1 match, although the half-wave line itself preserves rather than transforms its terminating impedance.",
|
||||
"source": "https://50ohm.de/NEA_umwegleitung.html#AG423",
|
||||
"confidence": 8
|
||||
},
|
||||
"AG424": {
|
||||
"revision": 2,
|
||||
"explanation": "Each folded-dipole terminal is about 120 ohms to ground; the half-wave detour preserves magnitude but reverses phase, so the two 120 ohm paths combine to 60 ohms.",
|
||||
"revision": 3,
|
||||
"explanation": "The folded dipole has about $240\\,\\Omega$ between its terminals, or roughly $120\\,\\Omega$ from either terminal to the electrical centre. One terminal is reached directly and the other through a half-wave line, which preserves impedance magnitude but adds $180^\\circ$. The two $120\\,\\Omega$ paths then appear in parallel at the coax input, giving about $60\\,\\Omega$.",
|
||||
"source": "https://50ohm.de/NEA_umwegleitung.html#AG424",
|
||||
"confidence": 8
|
||||
},
|
||||
@@ -3891,8 +3891,8 @@
|
||||
"confidence": 8
|
||||
},
|
||||
"AI402": {
|
||||
"revision": 2,
|
||||
"explanation": "The two directional detector branches for forward and reverse power identify the circuit as an SWR meter.",
|
||||
"revision": 3,
|
||||
"explanation": "The directional coupler creates separate small RF samples proportional to forward and reflected waves. Each diode-capacitor branch rectifies one sample to DC, and the meter circuit compares the resulting levels. Two directional detectors labelled for forward and reverse power identify an SWR meter.",
|
||||
"source": "https://50ohm.de/NEA_swr_meter_2.html#AI402",
|
||||
"confidence": 8
|
||||
},
|
||||
@@ -4016,14 +4016,14 @@
|
||||
"confidence": 8
|
||||
},
|
||||
"AI608": {
|
||||
"revision": 2,
|
||||
"explanation": "The circuit terminates the RF path and rectifies a known sample voltage, so it is a measuring head for RF power.",
|
||||
"revision": 3,
|
||||
"explanation": "The input is terminated by the resistor network so the transmitter sees a known RF load. A small voltage from that load is then rectified by the diode and smoothed by the capacitor for a DC voltmeter. Because a known resistance and detected RF voltage allow power to be inferred, the circuit is an RF power-measuring head.",
|
||||
"source": "https://50ohm.de/NEA_sender_messungen.html#AI608",
|
||||
"confidence": 8
|
||||
},
|
||||
"AI609": {
|
||||
"revision": 3,
|
||||
"explanation": "The measuring head is not rated for the full expected 15 W directly; a 20 dB, 20 W attenuator reduces both level and risk.",
|
||||
"revision": 4,
|
||||
"explanation": "The detector head can accept only a small RF power, whereas the transmitter is expected to produce about $15\\,\\text{W}$. A $20\\,\\text{dB}$ attenuator reduces power by a factor of 100, bringing the detector input to about $0.15\\,\\text{W}$, and its $20\\,\\text{W}$ rating safely absorbs the incident power. It therefore belongs ahead of the measuring head.",
|
||||
"source": "https://50ohm.de/NEA_sender_messungen.html#AI609",
|
||||
"confidence": 8
|
||||
},
|
||||
@@ -4040,8 +4040,8 @@
|
||||
"confidence": 8
|
||||
},
|
||||
"AI612": {
|
||||
"revision": 2,
|
||||
"explanation": "Detector diodes, resistors and layout introduce systematic errors, so accurate RF power readings require calibration correction values.",
|
||||
"revision": 3,
|
||||
"explanation": "The calculation assumes exact load resistance, diode drop and peak detection, but real diode characteristics vary with level and frequency and the physical layout adds stray reactance. Those errors belong to the complete measuring head, not to one ideal component value. Accurate RF power measurement therefore requires calibration correction values for the assembled circuit.",
|
||||
"source": "https://50ohm.de/NEA_sender_messungen.html#AI612",
|
||||
"confidence": 8
|
||||
},
|
||||
@@ -6879,8 +6879,8 @@
|
||||
"confidence": 8
|
||||
},
|
||||
"EF101": {
|
||||
"revision": 3,
|
||||
"explanation": "This is a detector receiver (crystal set style). The LC tuned circuit selects one AM station, and the diode rectifies the RF envelope so headphones can reproduce the audio; there is no local oscillator, mixer, IF stage, or active RF/audio amplification.",
|
||||
"revision": 4,
|
||||
"explanation": "Follow the received signal component by component. The antenna excites the parallel coil and variable capacitor; at their resonance one station is selected. The diode then passes one RF polarity, turning the AM waveform into current pulses whose amplitude follows the audio envelope. The high-impedance headphones cannot follow the individual RF cycles and respond to that slowly changing envelope as sound. With no battery, oscillator, mixer, IF strip, or active amplifier, this is the classic detector receiver.",
|
||||
"source": "https://50ohm.de/NEA_detektorempfänger.html#EF101",
|
||||
"confidence": 8
|
||||
},
|
||||
|
||||
Reference in New Issue
Block a user