LRDG Wireless set up

[Charlie Down]

I recently got sent a photo of a Y Patrol Wireless truck in connection with something unrelated (apologies the photo is from a private collection and I can’t post it).
The photo showed a wireless operator sending/receiving a signal on his No11 set. What struck me was that the other truck (Chevrolet 1533X2) was parked so close to the wireless truck. It reminded me of another well-known photo of an identical arrangement (attached). The trucks only just allow the operator to fold down his work shelf and stand in front of it with his back to the other fender. The trucks are aligned so that the driver’s seats are as close as possible to each other. It’s a very cramped set up considering they have hundreds of miles of empty desert to park in, and that they should be dispersed for camouflage, and so they present a minimal target should they be spotted by aircraft, as seen in most photos of a Patrol laying up for the night
So it strikes me that there had to be a reason for it. It is too deliberate and precise to be chance.
In front of the driver’s seat on the floor panel is a battery inspection hatch. The arrangement reminds me of how you would place 2 vehicles to jump start one of them. So is this a Wireless power issue, or a wireless causing flat batteries and the other truck is on standby to jump start it? Would the use of the Wireless cause the battery to loose so much charge that it would need jump starting? If so what is the point of the spare battery on the side step of a wireless truck? Or is it for some completely different reason?
My knowledge of WW2 Radios is limited so hopefully someone with greater knowledge/experience can chip in.
Something else I noticed that I didn't expect is that the aerial is connected to the wireless only when the wireless is in operation and is plugged into the front of the wireless and out the front of the wireless compartment. I have always assumed the aerial and cables were 'properly' wired into the body, through various holes in panels and eventually the wireless. This set up means that the Patrol couldn't send/receive messages when on the move (ignoring the issue of connecting headphones into the wireless at the same time!).

Picture24.jpg

[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