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Shack technology
Terms you hear while setting up and while hunting faults.
- SWR
- standing wave ratio, measure of the match between feed line and antenna
- Rückflussdämpfung
- how much weaker the reflected wave is, in dB (return loss); 9.5 dB corresponds to SWR 2, 14 dB to SWR 1.5
- Smith-Diagramm
- circle chart where every impedance has its place: centre = matched, edge = everything reflected, top inductive, bottom capacitive; try it out at /smith
- Güte
- ratio of reactance to loss resistance of a component or circuit (Q); a coil with 700 Ω and Q 50 has 14 Ω loss, the higher Q, the narrower a tuned circuit
- Bode-Diagramm
- curve of attenuation (and phase) against frequency, with frequency on a log scale; shows where a filter passes and how steeply it rolls off
- Tiefpassfilter
- passes everything below the cut-off frequency and attenuates above it; between power amplifier and antenna it keeps the harmonics back, try it out at /filter
- Butterworth
- filter response with no ripple in the passband, 3 dB down at the cut-off frequency, then 6 dB per octave steeper for each order
- Tschebyscheff
- filter response with a small, intended ripple in the passband (about 0.1 dB), in return much steeper than Butterworth for the same order
- Welligkeit
- in a filter, the ups and downs of the passband curve within the band, in dB; 0.1 dB corresponds to an SWR of up to about 1.36
- Einfügedämpfung
- how much power a filter or component costs in the passband, in dB (insertion loss): losses in coils and capacitors plus mismatch
- L-Glied
- matching network of two components, one in series and one in parallel; with the coil in series and the capacitor in parallel it is a low-pass filter at the same time
- Träger
- unmodulated oscillation on one frequency; in the waterfall a thin, even line
- Schaltnetzteil
- the most common source of interference in the shack: a comb of evenly spaced lines or a broad carpet that disappears when you switch off the power supply
- OTH-Radar
- over-the-horizon radar on HF, 10 to 40 kHz wide, often with a hard rhythm; also gets into the amateur bands and is reported by the IARU monitoring system
- Antennentuner
- matches the impedance, but does not turn a poor antenna into a good one
- Balun
- transition between a balanced antenna and an unbalanced feed line
- Unun
- transformer between two unbalanced systems, often used with end-fed antennas
- Mantelwellensperre
- stops current on the outside of the coax shield and with it RF in the house
- PEP
- peak envelope power, the way the limits are specified
- ERP und EIRP
- radiated power, relative to a dipole or to an isotropic radiator
- dBd und dBi
- antenna gain relative to a dipole or an isotropic radiator, difference 2.15 dB
- Verkürzungsfaktor
- factor between free-space wavelength and physical length; RG58 has 0.66, one metre of it takes 5.05 ns, try it out at /leitung
- Wellenwiderstand
- ratio of voltage to current of a wave on the line (Z0), depends only on the construction, not on the length; coax is usually 50 or 75 Ω
- Reflexionsfaktor
- share of the wave that is reflected at a discontinuity: Γ = (Z − Z0) / (Z + Z0); 75 Ω on 50 Ω gives 0.2, open 1, short −1
- TDR
- time domain reflectometer: sends a steep step into the cable and shows when and how strongly echoes come back, so where the cable ends or is damaged
- Stehende Welle
- superposition of forward and reflected waves on a mismatched line: peaks and nulls λ/4 apart stand still, their ratio is the SWR
- Rauschzahl
- how many dB a stage degrades the signal-to-noise ratio with 290 K at the input; a cable with 3 dB loss has a 3 dB noise figure, try it out at /empfangskette
- Rauschtemperatur
- noise of a stage expressed as the temperature of a resistor at the input: Te = 290 K · (F − 1); a 0.5 dB noise figure is 35 K, 1 dB 75 K, 3 dB 289 K
- Friis-Formel
- noise of stages in cascade: Te = Te1 + Te2 / G1 + Te3 / (G1 · G2) + …; each stage only counts divided by the gain before it, which is why the preamp belongs at the antenna
- Antennentemperatur
- noise the antenna brings along, as a temperature: cold sky at 10 GHz a few K, a dish seeing the ground in its side lobes 30 to 60 K, on HF up to millions of K because of band noise
- G/T
- figure of merit of a receiving system: antenna gain in dBi minus 10 log of the system temperature, in dB/K; more gain and less noise help equally
- LNB
- low noise block converter at the focus of a dish: amplifies and converts 10 GHz down to an intermediate frequency the cable can handle; for QO-100 usually with a 9750 MHz oscillator
- Belegte Bandbreite
- range containing 99 % of the transmitted power, half a percent stays outside on each side; for the adjacent channel the width at −40 or −60 dB says more, try it out at /modulation
- Tastklick
- clicks next to a CW signal because the carrier is switched on and off too hard; with a 5 ms soft edge instead of hard keying the width at −60 dB shrinks from several kilohertz to a few hundred hertz
- Splatter
- spill-over of an overdriven SSB or AM signal: the power amplifier limits, and mixing products appear next to the channel
- Carson-Regel
- rule of thumb for FM bandwidth: 2 · (deviation + highest audio frequency); 2.5 kHz deviation and 3 kHz audio give 11 kHz
- Modulationsindex
- in FM the ratio of deviation to audio frequency (β); at β = 2.405 the carrier vanishes, in AM the modulation depth goes by this name
- Intermodulation
- mixing products of two strong signals in a stage that is not quite linear; the 3rd order at 2·f1 − f2 and 2·f2 − f1 lands right in the band
- IP3
- 3rd-order intercept point: where the lines of the wanted signal (slope 1) and the 3rd-order products (slope 3) would cross; IM3 = 3 · P − 2 · IIP3, the higher, the better
- Dynamikbereich
- range between the noise of a receiver and the level at which intermodulation rises out of the noise: 2/3 · (IIP3 − noise)
- Superhet
- superheterodyne receiver: mixes the signal with an oscillator to a fixed intermediate frequency, where the sharp filters sit
- Zwischenfrequenz
- fixed frequency after the mixer of a superhet (IF), for example 455 kHz, 9 MHz or 45 MHz
- Spiegelfrequenz
- second frequency that gives the same IF in a superhet: two IFs away from the wanted signal, on the other side of the oscillator
- Vorselektion
- filter ahead of the mixer of a superhet that attenuates the image frequency and other spurious responses; after the mixer nothing helps any more
- Endfed
- wire antenna fed at one end, usually with a transformer
- Groundplane
- vertical radiator with radials as counterpoise
- Yagi
- directional antenna with directors and reflector
- Magnetic Loop
- small, narrowband loop antenna, often for cramped locations
- QRP
- operating with 5 W at most, often as a challenge in itself
- Shack
- the radio room
- CAT
- Computer Aided Transceiver: commands a computer uses to control the radio over USB or the serial port; Yaesu and Kenwood send text such as FA014074000;
- CI-V
- Icom's CAT: short data frames of bytes with the radio's address (IC-7300: 94h), over USB or a two-wire bus that several radios can share
- Speicherkanal
- stored frequency with mode, offset, tone and name, called up on the radio with a turn of the knob; you can program it in Rigstudio
- Bandstapelregister
- Icom remembers the last three settings per band (frequency, mode, filter); the band button jumps to the one used last
Related
Calculators Measure an antenna Simulators Transmission line in the time domain Receive chain Modulation and superhet
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