LTT-4 Transmitter

Frequency range: 260 to 520 KHz
Modes: CW and MCW
Power output: 150 watts CW, 110 watts MCW
MCW sidetones: 500, 700 or 1,000 Hz
Frequency control: 3 preset frequencies controlled by master oscillator.
Nameplate Data:
    Primary power 115 VAC , 6 amps, 60 Hz.
    Marconi designator: LTT-4  #84010A
    Spec: 81390
Transmitter Dimensions: 24" W x 20" D X 44" H
Transmitter weight: 360 pounds
Power Unit Dimensions: 21" X 11.5" x 14"
Power unit weight: 84 pounds
Circa: The schematic date is illegible. Either 1934 or 1939. Suspect 1939 is correct.
Comment: Except for the external power unit, the LTT-4 appears to be nearly identical to the LTT-1.

The LTT-4 operates on three preselected frequencies in the range of 260 to 520 KHz (1150 to 580 metres) by means of single bandchange switch.  A keying relay provides "break in" operation up to 45 wpm. The transmitter itself comprises of a self-controlled master oscillator stage (#10 triode tube) driving a neutralized push-pull RF stage which employs #211 tubes. An additional stage using a #10 tube provides tone generator functionality for MCW mode.

ltt4_tx_with_ps.jpg
On account of its bulk, the copper oxide rectifier (right) for the high voltage is mounted in a separate case and hardwired to the transmitter.  The bandswitch is in the very centre of the unit. 
ltt4_front_door_open.jpg
Note the #211 tubes on the first deck towards the left side. The #10 triode tubes are in close vicinity. 
ltt4_power_supply_cover_off.jpg
Copper-oxide, power rectifier unit with cover off. The power unit comprises of thirty two sections, wired in full wave rectifier fashion, which provide 1000 volts at 500 ma.
All photos in this table courtesy Laval Desbiens via SPECTRALUMNI  

 
ltt4_211_tubes.jpg ltt4_10_triode.jpg
The LTT-4 employed a pair of 211 tubes in the RF output stage. This type is also known as type VT-4C. (E-bay photo) 10 triode. (Courtesy Tube Depot)
Type 211 characteristics: Transmitting triode. Filament draws 3.4 amps at 9-10 volts. Types "A", "B" and "C" designate filament current. Type "D" has a constant voltage filament (10 volts at 3.25 amps). An "E" type  is a "D" type with parasitic-supressor chokes built into the grid and plate leads.

Type 10 characteristics: Power triode. FIlament power 7.5 volts @ 1.25 amps. Plate voltage 425 V max @18 ma. Power output 1.6 watts.

USEAGE
It is confirmed that the LTT-4 saw service aboard the now historic ships CCS Acadia and RCMP St. Roch. Not confirmed at this time but four pre-WWII minesweepers had LTT-4 transmitters  mated with National HRO receivers.
ltt4_erniefalvey.jpg
Ernie Falvey, VE1HA, operating Camperdown Radio VCS September 1949. At the left is the Marconi TM-11. The transmitter in the corner behind Ernie's left shoulder is the LTT-4. (Photo via Spud Roscoe)

 
ltt4_stroch.jpg
The LTT-4 installation (rightmost unit) aboard RCMP St. Roch in Vancouver. The tall unit to its left is the 200PT. (Image courtesy Vancouver Maritime Museum)
 
LTT-4 Operator's Manual - PDF  (Courtesy Laval Desbiens via Spectral Alumni)

Contributors and Credits:

1) Spud Roscoe <spudroscoe(at)eastlink.ca>
2) Vancouver Maritime Museum Curator   <collections(at)vancouvermaritimemuseum.com>
3) SPECTRALUMNI http://www.SPECTRALUMNI.ca
4) Laval Desbiens <desbiens.laval(at)videotron.ca>
5) 10 triode photo courtesy Tube Depot.  http://www.tubedepot.com/nos-10.html
 

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May 10/08