Vacuum Tube (Valve) Radio and Audio Repair Guide: Common abbreviations

Notes: this list is not exhaustive but it does cover most of the terms used in the vintage radio era and which will be found in literature and receiver circuit diagrams of the period. In some cases alternatives have been given for abbreviations but others might well be found to have been used. In particular there seems to have been a fairly free interchange of upper and lower case, or of normal or italic letters in different publications (sometimes even in the same!) but as with certain other ambiguities the context will usually show which particular interpretation should be used. Tube (valve)makers’ data books used a large number of abbreviations, of which are shown here only the few that are also used generally in vintage radio.

The writer makes no apology for omitting more modern abbreviations which are inappropriate to vintage radio.

A or AE Aerial. Note: the old spelling used a diphthong, viz. IErial.

AE See above.

A or an Anode. The context will usually prevent confusion with aerial.

‘A’ battery The American term for an LT battery.

AC Alternating current.

AC/DC Receiver suitable for either AC or DC mains.

AF Audio frequency

AFC Automatic frequency control. A or Amp Ampere.

Ah Ampere hour. In vintage radio this is used exclusively to indicate the capacity of an accumulator.

AM Amplitude modulation. Amp Amplifier.

Amps Amperes.

ANT Antenna, the American term for aerial.

AVC Automatic volume control.

AVO The trade name of the best-known test meter, supposedly derived from Amps, Volts,

Ohms and used by radio engineers since the 1920s.

Now virtually a generic term for test meters.

‘B’ battery The American term for an HT battery.

BC Broadcast (band), the American term for medium waves.

C Capacitor or capacity.

‘C’ battery An American term for a grid bias battery.

cps, Hz or cs Cycles per second.

CRT Cathode ray tube

CW Continuous wave.

dB Decibel.

DC Direct current.

DDT Double-diode-triode (valve).

Det Detector.

E Earth.

E Used to indicate voltage, e.g. Ea = 90V.

EHT Extra high tension.

EMF Electromotive force.

f or f Frequency.

FC Frequency changer (valve).

FM Frequency modulation.

g Grid (of valve). May be followed by a number.

gc Conversion conductance (in frequency changer valve).

GB Grid bias.

gm (Valve) mutual conductance.

GND Ground, the American term for earth.

H Henry.

HF High frequency.

HT High tension.

I or I Used to indicate current (see below).

Ia Anode current (valve). IF Intermediate frequency. IFT Intermediate frequency transformer.

Ig2 Screen grid current (valve).

Ik Cathode current (valve).

K Cathode (of valve).

kc, kcs or kHz Kilocycles per second

K ohm kilohms (= 1000 ohm)

omega. See also M ohm for American usage.

y Wavelength, e.g. y = 300 meters.

L Inductance.

LF. Low frequency.

LO. Local oscillator (in superhet).

LS. Loudspeaker.

LT. Low tension.

LW. Long wave.

p (Valve) amplification factor. Also used generally to indicate a subdivision by 1 000 000.

M meters.

mA, ma or M/a Milliamp — one thousandth of an ampere.

Ma/V Milliamps per volt (in valve).

uA Microamp.

MCW Modulated continuous wave.

mfd or uF (mu) Microfarad.

MIC or mic Microphone.

mmfd or p Micro-microfarad (= picofarad). MSW Medium short waves (band: also known as trawler band).

mV Millivolt — one thousandth of a volt.

uV Microvolt — one millionth of a volt.

MW Medium waves.

M-ohm Megohms (= millions of ohms). Note: in American radio circuits M indicated not meg but mu and 1 M 1000 ft

Neg Negative, as in voltage.

Ohm (omega) Sometimes used to indicate ohms instead of omega when the printer did not have a set of Greek letters!

OC or o/c Open circuit — used as adjective, noun or verb in respect of a break in a circuit.

Osc Oscillator.

P Plate (in valve) or Power.

PA Public address.

PB Pushbutton.

PD Potential difference. Essentially the same as voltage but is handy for describing the change of voltage from one point in a circuit to another.

Pen. Pentode.

pfd. Picofarad (pF)

PM. Permanent magnet.

Pos. Positive, as in voltage.

Pot. Potentiometer.

PU. Pick-up (gramophone).

QPP Quiescent push-pull.

ra or rA Anode resistance = impedance of valve.

R or R Resistance or resistor.

RA Recommended value of load resistance or impedance for valve.

RCC Resistance-capacity coupled.

Rec Receiver (sometimes Rectifier).

Rect Rectifier.

RF Radio frequency.

Rg Recommended or actual value of resistor used to return grid of tubes (valves) to chassis or cathode

Rg2 Recommended or actual value for resistor used to supply voltage to screen grid of valve.

Rk Recommended or actual value of cathode bias resistor for valve.

RMS or r.m.s Root mean square (value of AC voltage).

RT or R/T Radio telephony.

S or Sw Switch.

SC or s/c Short circuit. May be used as adjective, noun or verb in respect of a breakdown in insulation in a circuit.

SG Screen grid.

Sig. gen. Signal generator.

Spkr. (Loud) speaker.

SW Short wave.

TI or t.i. Tuning indicator.

Trans. Transformer.

TRF Tuned radio frequency.

UHF Ultra high frequency.

USW Ultra short waves.

V Valve.

V or v (following numeral) Volt(s).

Va Recommended or measured anode voltage in valve.

VC or vc Volume control.

Vf Filament voltage (valve).

Vg2 Recommended or measured screen-grid volt age in valve.

Vh Heater voltage (valve).

VHF Very high frequency.

VT Vacuum tube, the American term for valve.

W Watt(s).

W/C or wc Wave change (switch).

X Used to indicate reactance, e.g. X 400 c

Z Used to indicate impedance, e.g. Z = 400 C

Omega -- Ohms. Note: prior to about 1930 the lower case omega was used to indicate ohms and C was used as for millions of ohms or megohms. See also Mci.

Greek and Latin prefixes used to indicate the number of electrodes in a particular valve.

Note: this does not indicate the number of base connections.

Diode Two electrodes.

Triode Three electrodes.

Tetrode Four electrodes.

Pentode Five electrodes.

Hexode Six electrodes.

Heptode* Seven electrodes.

Octode Eight electrodes.

Two or more prefixes may be combined to indicate multiple tubes (valves), e.g. triode-hexode.

==

Also known in America as pentagrid.

Some sources suggest that certain individuals may be able to hear frequencies as high as 30 kHz.

==

Ranges of frequencies commonly used in vintage radio

Audio frequency (AF) is normally taken as the range of frequencies audible to the human ear, i.e. from about 16 Hz to 16000 kHz. In vintage radio low frequency (LF) may be taken to mean the same.

High frequency (HF) may be taken as a general term for anything above about 16000 Hz, i.e. above AF. The alternative radio frequency (RF) is more

or less synonymous in vintage radio, e.g. HF amplifier is the same as RF amplifier. In receivers designed specifically for commercial or military communications extra low frequency (ELF) may be used for frequencies below about 30kHz.

Intermediate frequency (IF) as used in super heterodyne receivers is not in itself a term for a specific group of frequencies but for the particular frequency used in a particular. However, the choice is limited and 99.9% of the IFs used in vintage AM receivers lie within the ranges of 100 kHz to 140 kHz or 450 kHz and 470 kHz. The odd exceptions included 175 kHz, 265kHz and 360 kHz, but others may have been used. Vintage FM receivers nearly all used a 10.7 mHz IF but again the occasional oddity may be found.

The definition of very high frequency (VHF) and of ultra high frequency (UHF) has changed considerably over the vintage years. Before about 1940 anything over 30mHz was considered to be VHF, whilst above 60 mHz was UHF. By about 1944 VHF covered up to around 100mHz and UHF up to around 200 mHz. Ultra short wave (USW) covered more or less anything above 30 mHz; for instance it was usual to refer to the original BBC 405-line television service on 45 mHz as being USW.

Some obsolete radio terms which may be encountered in old literature

Anode battery An HT battery.

Gramophone attachment A pick-up.

Grid leak A high value resistance used to return the grid of a tube (valve) to filament, cathode or chassis.

Mansbridge capacitor A type of paper con denser noted for having a good capacity to size ratio.

Note magnifier An AF amplifier. Power tubes (valves) An output valve.

Telephone capacitor A tone control capacitor shunted across a loudspeaker.

V Indicates the detector (it may have stood for valve) and is a formula once used to describe receivers, e.g. a 1 -V-2 set had four tubes (valves), one prior to the detector and two following it.

An 0-V-0 was a one- tubes (valves) set. Wet battery An accumulator.

X Used widely as an abbreviation for the first few letters of a radio term which could be guessed from what followed. For instance, Xtal meant Crystal, Xmitter meant Transmitter and Xformer meant Transformer.

Some colloquialisms used in vintage radio

Belt Electric shock.

Bike A cycle, e.g. the UK mains frequency of fifty bikes.

Bottle Valve.

Burn up The disastrous failure of a component resulting in its being reduced to ashes; often the outcome of a dead short (q.v.).

Cs and Rs Capacitors and resistors.

Dead short A zero-resistance short circuit of a potentially calamitous nature (cf Short).

Deck Chassis.

Diddlyode Diode.

Fils Filament(s).

Freak Frequency changer.

Gain pot An RF gain control (cf Pot). Genny Signal generator.

Iffy IF transformer.

Leak, leaky An unintentional resistance path of potentially harmful nature, e.g. a leaky capacitor is one that permits the passage of DC through it. Not to be confused with the completely intentional grid leak (q.v.).

Lining up (job) Realigning the tuned circuits of a receiver, esp. a superhet.

Mike Microphone.

Mikey (component, esp. a valve) Emitting a ringing sound when tapped or subjected to vibration.

Mod, hum Modulation hum, a 50 Hz or 100 Hz hum that appears to be tuned in with a radio signal.

Neon A screwdriver incorporating a small neon lamp to give indications of voltage, esp. for checking the chassis of AC/DC receivers.

Open Open circuit.

Pot Potentiometer. Not to be confused with tea pot, one of the most essential items in any workshop.

Puffer Small capacitor of picofarad value.

Reccy Rectifier.

Short Short circuit, e.g. a short on the HT line, but not necessarily of a calamitous nature, such as in high resistance short (cf Dead short). Soak (test) Leaving a receiver running in the workshop for a very long time to see if anything fails.

Stopper A low value resistor inserted into the grid, screen grid or anode circuit of a tube (valve) to prevent self-oscillation.

Terminal (screwdriver) Used in certain areas only to indicate a narrow bladed screwdriver for use with electrical terminals.

Tranny Transformer, e.g. mains tranny, auto tranny.

Trolly Electrolytic capacitor.

Wob, Wobbulator (frequency modulated oscillator).