One question. One answer. Zero noise.
For an ideal inductor, voltage reaches its peak one-quarter cycle before current does, so voltage leads current by 90 degrees.
Low-voltage ceramic capacitors are widely used in part because they are comparatively inexpensive.
A repeater normally receives on one frequency and retransmits on another. The spacing between those two frequencies is the repeater offset.
Messages intentionally encoded to obscure their meaning cannot be transmitted over an amateur radio mesh network.
The most common amateur-HF RTTY shift is 170 Hz between mark and space tones.
FT8 is designed for reliable communication at very low signal-to-noise ratios, making it effective for weak-signal contacts.
At 14 MHz, a 38-picofarad capacitor has about 299 ohms of capacitive reactance. The impedance is therefore about 400 - j299 ohms, which corresponds to Point 4 on Figure E5-1.
For a sine wave, Vpeak = Vrms × √2 and Vpp = 2 × Vpeak. With 120 volts RMS, Vpp is about 339.4 volts.
A Class A common-emitter stage is biased roughly halfway between cutoff and saturation for symmetrical signal swing.
You must transmit your assigned call sign at least every 10 minutes during a communication and again at the end.
Two 220-microfarad capacitors in parallel total 440 microfarads. Two 1-megohm resistors in parallel total 500 kilohms. Their RC time constant is 0.000440 × 500,000 = 220 seconds.
Wire-wound resistors behave partly like inductors because they are made from coiled resistance wire. At RF, that inductance can make circuit behavior unpredictable.
Resistance opposes current flow regardless of whether the current is direct, alternating, or at radio frequency.
In Figure E6-3, symbol 2 is the NAND gate.
Higher symbol rates require the system to change states more quickly, which needs wider occupied bandwidth.
The alpha cutoff frequency is where grounded-base current gain has fallen to about 0.7 of its low-frequency value.
Analog AM fast-scan television uses a video channel roughly 6 MHz wide, far broader than ordinary voice or data modes.
The absolute inverting gain is RF/R1, giving about 14.
LUF means Lowest Usable Frequency for communication between two specific points.
IRLP nodes are commonly controlled over the air with DTMF commands sent from the user's radio.
A varactor diode is operated so its junction capacitance varies with applied reverse voltage, making it a voltage-controlled capacitor.
FT8 transmissions use tightly synchronized time slots, so the computer clock must be accurate to roughly one second.
A noise figure around 0.5 dB is typical of a good low-noise UHF preamplifier.
Component 1 in figure T-1 is the standard zigzag resistor symbol.