LTT-4 Transmitter (Longwave Telegraph 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.
Primary power 115 VAC , 6 amps, 60 Hz.
Marconi designator: LTT-4 #84010A
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.
|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.|
|Note the #211 tubes on the first deck towards the left side. The #10 triode tubes are in close vicinity.|
|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|
|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.
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.
|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)|
|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