The T1154 was developed in
the late 1930s for the RAF and entered service in June 1940. Over 80,000
were made before manufacture finally ceased in 1950. It is immediately
recognised by the brightly coloured control knobs. The transmitter was
designed by Marconiís Wireless Telegraph Co at the aeronautical
laboratory at Writtle. The design was typical of the innovation at the
time and used the then new dull emitter filament technology for the two
large power amplifier valves. The transmitter provided telegraphy and
telephony with very good speech quality.
It was used together with the companion receiver R1155 in a wide range
of aircraft including the Lancaster, Halifax, York, Varsity, Mosquito,
Valetta, Shackleton and Wellington.
The T1154 contains 4 valves and is a variable frequency, master
oscillator/power amplifier type of transmitter and is capable of
generating a radio frequency (RF) output power of 45 to 70 Watts on CW (morse)
and 14 to 17.5 Watts on speech and MCW. It had slightly different
frequency coverage to the receiver using three or four switched bands
and typically covers 0.2- 0.5 MHz, 3.0 - 5.5 MHz, 5.5 - 10 MHz. The
4-band models split the bands slightly differently and provided coverage
up to 16.7 MHz.
Transmit modulation modes
are: Amplitude Modulation (AM) for speech plus Continuous Wave (CW) and
Modulated Continuous Wave (MCW) for Morse code transmission. The peak
modulation is approx. 70 per cent using suppressor grid modulation on
both MCW and R/T. The microphone used was either a Carbon granule type
or electro-magnetic, using sub-modulator A1134 or A1134A.
The valve line-up is Master Oscillator, sidetone and modulator - two
VT105 indirectly-heated triodes; RF Power Amplifier - two VT104
The Antenna System was a
fixed wire aerial for HF frequency ranges and a long wire trailing
aerial for MF frequency ranges.
In airborne installations, both receiver and transmitter were powered by
two rotary transformer power supplies which were driven from the
aircraft electrical system of 12 Volts or 24 Volts. One transformer unit
provided the high tension (HT) and low tension (LT) supply for the R1155
receiver and the LT supply (6V at 4A LT plus 6 volts at 2.5A for the
keying relay) for the T1154. The high voltage HT supplies for the
transmitter (1200V at 200mA) were provided by a separate rotary
The transmitter measures 17 1/2" wide, 16 3/8" high, 11 1/4" deep and
weighs 46 lb 10oz.
The picture shows an T1154
(top) and below it, one with its companion R1155 installed in the
Brooklands Vickers Varsity.