[SOC] did they make those mcw gizmo's out of wood or plastic?

[g4jht]

Note If the attachment which is a picture of a Marconi Marine Relient 
Emergency Tx does not make it through and you would like it send me a PM 
(dja.)

Your talking 1940s, 1950s technology. Not wood or plastic but cadmium 
plated steel. Your talking about 4 ft or 6 ft 19 inch steel rack, 
cadmium/copper plated steel chassis, G9A Loctal socket for the EF50 
crystal oscillator, and 5 pin ceramic tube bases for the 807s.

After the oscillator you have a 807 doubler (the oscillator runs at half 
carrier frequency), then an 807 driver ,a PA of  three 807s in parallel 
(class C) for 100 watt of RF, and two 807 as a 500 cycle self exiting 
oscillating modulator with choke modulation to the PA.

To prevent "chirp" caused by sluggish oscillator starting if it was 
keyed. The half crystal frequency oscillator output is simply grounded 
on key-up, and all the other stages  in the RF chain are keyed in normal 
fashion, this provides bright crisp MCW without a backwave.

This rig I describe would survive the shock of self defense weapons 
being fired, or  a torpedo hitting the ship midships and still be 
operational to permit getting a distress message off.

The PA stage/aerial circuit is interesting. The RF from the three 807s 
in  class C  with parasitic stoppers in each plate circuit goes through 
a 0.1 uF 2000 V cap  to the junction between a variometer connected to 
the antenna terminal on the top of the set and a RF (hot wire) ammeter 
(4 Amps FSD) then to a 50 to 500pF wide spaced (HV) variable capacitor 
connected to ground.E  The variometer tunes the antenna to resonance 
while the variable (coupling) capacitor adjusts the Tx  loading hence 
power output.

The whole thing can run off either a mains (AC or DC) motor generator 
set. Or in emergency mode off 24 volt DC from batteries and a separate 
24V rotary inverter providing +250V DC, and +800V DC for PA plates.

The batteries are placed high up in the ship so that together with the 
wireless shack they are the last part to submerge. Lots of R/Os have 
drowned while sending out the distress message on sinking ships.
See attached picture. At the moment I do not have an electronic image of 
the circuit.
And later version may have had a pair of 6146s in the PA probably the 
modulator too.

Hope that helps 73, Dave

On 08/26/2018 05:09 PM, cptflak at foxinternet.com wrote:
> Dave, did they make those mcw gizmo's out of wood or plastic.
>
> Frank soc 1126
>
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