Landships II

kieffer · Commander in Chief

electric power generator

Rectalgia · Legend

That looks like a lot of power for a radio? Just ten - fifteen years later this is the type used in the Australian outback for the school of the air, transmitting hundreds of kilometres:

http://adaptivereuse.net/wp-content/uploads/images/traeger.jpg

Well, the kids' model was a bit more advanced, voice transmission so they didn't have to learn morse code first but still the same generator (they got fit too those children, while they took their lessons).

And if that is a radio aerial in your picture it needs to be higher. And that other contraption has nothing to do with radio that I can see - it looks more like a generator itself. Still, could be demonstration of two power sources for radio with just a demonstration aerial too and I guess those old spark-gap transmitters took a fair amount of energy. The pigeons were better (and more discreet). Spark-gap was broad-band and easily intercepted - but easily jammed too, in fact the engine of the generator would probably do a good job of jamming it.

The whole thing puzzles me.

kieffer · Commander in Chief

Hi Steve,
that's a great finding, the decent young fellow pedalling and transmitting!
A lot of power: people in WW2 were loading batteries with the help of a bicycle like the two on the photo, I heard that it was a tedious job. But that's a bit different I guess than generating power for radio/field telephone usage.
I guess you're right, the thing on the left looks like a petrol fired generator.
I think this photo is cut of on top, the pole probably longer than it looks. The guy in the wagon, probably the telegraphist? But if there must be a cable connection between his station to the next?

regards Kieffer

Rectalgia · Legend

Hi Kieffer,

Maybe it is a ground-current communicator demonstration. The earth itself is used instead of wires. Not bad for muddy battlefields. Needs moderate voltages and quite a few amps current probably, also powerful amplifier to recover the signal. Not affected by radio-spectrum noise like from engine magnetos and such and no wires to be damaged. Not all that easily intercepted due to limited range - but maybe not very reliable, ground conductivity can be quite low when it is dry.

The Germans had some equipment like that - see http://www.rkk-museum.ru/vitr_all/exhibits/922_e.shtml. Looks like someone is playing around with the concept again - see http://pe2bz.philpem.me.uk/Comm/-%20ELF-VLF/-%20ELF-Theory/Th-115-EarthCurrents/com.pdf, that has some technical data. For military use they probably used higher voltage and current for a little more range. Directionality would be hard to predict, surface geology is only a rough guide and sometimes misleading.

Much conjecture but it would make sense now. That van would contain the sending equipment (simple) and receiving gear (complicated) and operator. Enemy aviators would soon know to look for it so it would be camouflaged in the field I think - relays would be quite feasible, being the same equipment spaced along the line of communication to pick up and re-transmit the signal (giving good assurance of continuity since the sender would hear the next relay passing it on). The noisy engine generator could be used down the line where it is not so close for the enemy to hear.

Ha, after all that maybe it turns out to be something different but that's the best guess I can give now.

Rectalgia · Legend

Hi Kieffer,

kieffer wrote:

...the decent young fellow pedalling and transmitting! ...

As you might expect - the School of the Air operated at first in conjunction with the Flying Doctor Service (later Royal FDS) using the same radios on the FD network. Every remote homestead and police station had those radios - they still have the modern equivalent and now in vehicles and so-on as well. The Flying Doctor Service was established by the Australian Inland Mission which is run by the Presbyterian church. Bit before my time but all started by "Flynn of the Outback", a minister. I did meet numerous times the minister who took over the AIM from the Reverend Flynn.

Swords into ploughshares - radio and aircraft from WW1 developments immediately turned in use to helping people.

Steve

kieffer · Commander in Chief

Hi Steve,

that's completely new to me, the ground current thing, so thank you for bringing that up!
It all sounds a bit like the 'earth radiance' boxes, who people could 'install' in their houses or in the barn to divert negative energy.
But this, and the lead to that Russian? radio museum is highly interesting!

Morse: still widely used during the Cold War. Every signaller has it's 'own hand-writing' which can be identified rather soon by other listeners (it's the speed and rythm of the signalmans hand). On navy ships they had a rotation scheme, signallers shifted to other vessels so the link between ship and messages was more difficult to make.
Antenna length: I thought it isn't that much the height but the lenght, if I am correct a few meter height is enough but than you have to spread the cable horizontally.

regards Kieffer

Rectalgia · Legend

Yeah antenna length is best a simple fraction or multiple of wavelenth (give or take for some quality factor) which immediately shows problem with spark-gap - that is not particularly tuned for wavelength (everything going out, even microwave which they lumped together with infra-red spectrum in those days) but I guess there was a peak frequency or range. The antenna length would "sort of" tune the transmission to those frequencies closest to fractions and multiples of itself (through less losses than other frequencies) and if one of those corresponded to the peak frequency of the spark gap that would be best efficiency.

So that signal is more or less horizontally polarised (vertical antenna would be vertically polarised or maybe it is vice versa, no matter) but you still have to get height so the signal is not absorbed too much by the ground and other obstacles. Long wavelengths handle terrain effect better, shorter wavelengths are closer to line of sight, somewhere in the middle you get bounce effects from the troposphere, even "ducting" along that boundary, but that was all mysterious and trial and error back then, until transmission tuning got better and not all frequencies are suited to (comparatively) short-range ground-to-ground communication.

Steve

kieffer · Commander in Chief

Hi Steve,

I must pass here: my rather limited knowledge comes from fiddling a bit with a 'kristal' radio, listening in the night to obscure radio stations, beeps and mysterious voices.
My radio days in the service, well as an older private told me when I had to step in the truck, that brought me from the station to the barracks as a 1day old recruit:'yes we have radio's. You may look at it, not in it'.

regards, Kieffer

Rectalgia · Legend

I keep forgetting about the teeny size of countries in Europe biggrin

.� For longer-range, the bigger radios usually have an ATU "Aerial Tuning Unit" between the transmitter and the aerial.� This electronically adjusts the SWR "Standing Wave Ratio" of the antenna to suit the frequency being sent, which is optimising the harmonization of the antenna.� That is the practical solution of what I was talking about, radio works best when the antenna is a simple fraction or mutiple of the wavelength.� That can be emulated electronically.� More important/critical with some frequencies than others I am sure.

Surprisingly, the ATU needs to be used to trim to optimum each time used, even though frequencies might be unchanged and crystal locked (yes, echo of your crystal set).� I suppose air losses must come into it (humid air is less dense and more conductive, etc.).

kieffer · Commander in Chief

Rectalgia wrote:

I keep forgetting about the teeny size of countries in Europe .
...one of these teeny's has the tallest men (according the WHO or some institution) on the planet...
best wishes, Kieffer

Rectalgia · Legend

kieffer wrote:

...one of these teeny's has the tallest men (according the WHO or some institution) on the planet...

Just as well there's the European Union then - otherwise they'd be getting visas stamped every couple of steps they take. But, let me see, "Dinaric Alps", covering 7 countries - 1.856 m average at age 17 and measured too, not self-reported (men lie about measurements, the ladies say). Impressive.

...Steve

kieffer · Commander in Chief

Hi Steve,
erm... that's the Alps Steve, and it's not that teeny here that you can see these from my balcony. I've been there, could'nt stand right up in the mountain-bus. Decent hard-working people there but definitely: short, as in 'shorter than my breed'

regards, Kieffer

Rectalgia · Legend

Ah, but have you seen their 17 year-olds? Or is Wikipedia lying again? That would be nothing new - a veritable font of misinformation, is the internet - http://en.wikipedia.org/wiki/Human_height. Modern records in table near the top, for average heights of troops around/a little before WW1, see 3/4 way down "History of human height".

kieffer · Commander in Chief

I guess were back on the Food Theme again...and the old statistics (and for some period the only ones available) of the medical records of recruits.
If wikipedia is correct, I don't know. I can't find back the article on the measurements, which stated that Low Countryboys were at the top, may be a new outcome?
But in general: Danish, Swedish, Finnish and the northern part of Les Pays Bas (I think the Friesians were the tall boys) all these northern countries seem to have a 'growing' population, in length. As a matter of fact these weren't the smaller kind already.
But you're right: this all can be used to bragg, has been part of dubious ideologies and about age: being old seems less attractive today than being a young hipster..

regards, Kieffer