LRDG Wireless set up

[Grant Bowker]

Feel free to tell me I'm wrong - I don't claim to be a wireless expert.
I have the impression that the WS19 required 12V (or 24V) to operate. Most trucks of that era were 6V. Is it possible that to avoid carrying both wireless batteries and charging sets (on trucks that were already heavily loaded) they devised a scheme to connect the batteries of two trucks in series to give 12V?

[Charlie Down]

The wireless trucks carried a spare battery on the cab side step, so if they needed 12 volts then that would have been the obvious method of achieving it. Maybe for a long range signal they boosted the power to 18volts using another truck battery? Seems possible, but if so why not 24 volts? I just don't have that sort of knowledge. I know the Chevrolet 1533X2 Wireless trucks had a charging switch panel behind the drivers seat to manage the batteries (custom made most likely in Cairo, but I only have a vague idea of what it looks like after 5 years of looking for photos of it, see attached), so that took care of the 12v supply and charging them.

[Ron Pier]

Back then, 12 volts was often achieved with two 6V batteries wired in series. My knowledge is mainly to do with the 8cwt PU's. In these, the wireless was powered by two batteries whilst two more were being charged, either by built in generator or separate charger. The wireless was operated independently of the twin 6V vehicle batteries. Ron

[Charlie Down]

Hi Ron,
So the No11 set would use 12 volts from two 6 Volt batteries in series to power the set. On the LRDG trucks this would be achieved by using the truck 6 volt battery connected to the battery on the side step in series through the Charging Switch Panel.
Would there be any possibilty/need for a third battery to boost the signal for long range transmissions? And would sending the signal flatten the batteries sufficiently to require a alternative source of electricity to start the truck? Would the truck engine be switched off during signalling to prevent interference?

[David Dunlop]

Morning. Charlie.

Unfortunately, the idea of a third battery in the Wireless System to provide 18 volts to the wireless set will destroy said set. You would instantly burn out the heater/filaments in the sets valves which were designed with a very narrow +/- 12 volt operating range. The wireless set will have a theoretical operating range limit factored into its design that no amount of extra voltage will increase. A whole host of environmental factors may, however, increase/decrease range from time to time.

Wireless vehicles would definitely have had wireless suppression kits fitted to them to eliminate vehicle electrical interference with the wireless set. This was not necessarily done to other, none wireless fitted vehicles early in the war, but became much more common as the war progressed for several reasons, from both production considerations and bad experiences from vehicle operations in theatre. My thought would be that given the nature of the work the LRDG was doing, they would have wanted all vehicles wireless suppressed, either from the factory, or mods done upon receipt in the field. So the two vehicles being so close in your photo would not surprise me.

Keeping a pair of wireless batteries charged in the field by the LRDG would be an interesting challenge. The standard norm is a set of four 6 volt batteries. Two charged and running the wireless set while the second pair are being recharged through a charging system via some form of charging set. The charging set for the LRDG would likely be one of three things available to them: a small gasoline powered chorehorse, the vehicle generator from one of their vehicles, or perhaps a secondary mechanical generator driven either directly, or indirectly from the PTO of one of their vehicles. This latter option was often found in jeeps, during the war, mounted over the PTO assembly, between the two front seats.

Hope this helps a bit.

David

[Lynn Eades]

Some ramblings:
I would tender the idea that most early war radio equipped vehicles were 6 volt and carried a petrol gen set (300 watt chorehorse or Brit equivalent?) The U.S. would have been the first of the allies to go over to a 12 volt vehicle electical system to cater for "in house" radio support. The belt driven (pto) generator in the Jeep was the same Autolite (different end plates) generator that was fitted in the Dodge Radio Car from circa 1943 (as well as late carriers)
These comments with respect to 12 volt Jeeps, from a thread in G503:

The W7 modification is in the February 15, 1945 SNL parts book.

I know the 12v PTO units were in production and Navy contract radio jeeps delivered by Willys-Overland in May of 1943.

The following TM for radio installations implies the conversion was in use at least by January 1944.

I think the 12 volt conversion in a WWII jeep was not so common until quite late in the war? (my comment)

Obviously, the problem with having a 6 volt vehicle and a 12 volt radio is that you need a second 6 volt battery. Keeping two separately used batteries evenly charged is not so simple. To manage this for soldiers that were in majority, farm types, required some extra care and skills.
To this day there are somewhat complicated systems in motor homes.
The radio op. would have used an hydrometer to check the state of charge of his batteries. This can be a bit vague, without familiarity.
For an LRDG radio op., with vibration, heat and evaporation, he would have been constantly mothering his batteries.

All the above stated from a position of "not much knowledge"

[Ron Pier]

Lynn, like you without the benefit of huge knowledge, but from my own experience. My 1940 FFW Morris and Austin Tilly are both 12v which was supplied by twin 6v batteries wired in series.

The wireless batteries were kept charged by means of a PTO driven generator through a switchboard charging unit.

I would need to research other makes and models to confirm if this was the norm. Ron