Hi guys! I'd like to ask a few questions on WWII radio sets. I've been reading Battle for Manila, and there was some mention there (not a direct quote): Sometime in 1944, the Voice of Freedom had been picked up by long wave radio sets. Radio sets with short wave capabilities had been banned by the Japanese since 1941, which means that the signals must be coming somewhere close to Manila. (Leyte. The radiobroadcast was of Macarthur's return) From this information, am I right to assume that short wave radios have the ability to pick up signals outside the country while long wave can only get those within the country? I also read about the Japanese "re-conditioning" radio sets so it won't be able to pick up frequencies from the Allies. Can one "un-recondition" a radio set? And what did WWII radios, particularly those used by guerillas, look like? Thanks for reading!
Generally, you are right-- short wave transmissions tend to have a longer range than long and medium wave transmissions. That's why I can pick up shortwave radio stations from around the world, but AM usually is limited to the next country over. As to re-conditioning sets-- many early radio sets still in use in the WW2 period were tuned using crystals. You needed the right frequency crystal to receive on that frequency. So, simply removing all the crystals except for those you want people to be able to receive on could easily prevent them from receiving enemy transmissions. I don't know if this is what was done in the case you refer to, but I suspect it is. Doc
I'm sure it's possible to build an AM receiver for SW/LW without actually needing crystals; it's powered by the incoming radiation, so doesn't need an on/off switch. You just disconnect the aerial. Bear in mind that I haven't actually built one for about 30 years, so feel free to correct me; got a great little book somewhere tells you exactly how to do it, but haven't the faintest idea where I put it.
short wave transmissions tend to have a longer range than long and medium wave transmissions. many early radio sets still in use in the WW2 period were tuned using crystals. Hi Doc I never saw a crystal set in use, they were very rapidly phased out in the mid 1920s. I remember our 5 valve Bush wireless set arriving in the mid 1930s, and we had a valve set before that. The same was true of friends and relatives, so far as I recall. This was in England, but it was the same in Italy in WW2, the only sets I saw there were valve sets. The distance covered by radio waves depends on the power of the transmitter, not on the frequency. Long waves were the very first to be used and they transmit around the world. Now long waves are used mainly for navigation and for time signals. Very high waves are line-of-sight only, that's why TV transmitters are set as high as possible. It is medium waves which typically cover only a few hundred miles, unless bounced. A good ploy is to bounce them off the moon. Some excellent info here radio wave propagation Peter
Crystal sets were used during the war: BBC - WW2 People's War - Crystal Sets BBC - WW2 People's War - England and the English were never far from our minds Foxhole radio - Bizarre Labs
I'm sure it's possible to build an AM receiver for SW/LW without actually needing crystals; it's powered by the incoming radiation, so doesn't need an on/off switch. You just disconnect the aerial. Bear in mind that I haven't actually built one for about 30 years, so feel free to correct me; got a great little book somewhere tells you exactly how to do it, but haven't the faintest idea where I put it. POWs used to build shortwave receviers using thin wire as the aerial and someones filling as a power source. The speaker was a razor blade which vibrated.
POWs used to build shortwave receviers using thin wire as the aerial and someones filling as a power source. The speaker was a razor blade which vibrated. From: Foxhole radio - Bizarre Labs POW Radio Prisoners of war during WWII had to improvise from whatever bits of junk they could scrounge in order to build a radio. One type of detector used a small piece of coke, which was a derivative of coal often used in heating stoves. The piece of coke used was small, about the size of a pea. A small board was used and a depression was cut into it near one end to hold the coke. A screw and, if available, a screw cup were used to hold the coke in place. A wire lead to the receiver was run from this to the coil/aerial (see Set 5). A foot or so (30cm) of steel wire (guitar wire, piano wire, etc.) was wound around a pencil, long nail, or similar, leaving about one inch (25 mm) unwound at each end. The wire should be somewhat springy.A second screw and screw cup is set about 3 inches (75 mm) from the first. Attached by this screw are one end of the steel wire spring and a second lead, which is connected to one lead of the headphones or earphones (if anyone has any information on how earphones from these sets may have been improvised, I would like to hear about it). The steel spring wire was then stretched so that it just rested on the coke. After much adjusting of the point of contact on the coke and the tension of the wire, some strong stations would have been received. If the POW was lucky enough to scrounge a variable capacitor, the set could possibly receive more frequencies. Here's a another great description of a POW radio (it was hidden away in my link above) R G Wells: Index
Here's another great description of a POW radio (it was hidden away in my link above) Disguised as a box of toothpowder no doubt...
Crystal sets were used during the war Yes, you can make one now if you wish. This is quite different from commercial cat's whisker sets. They were phased out in the 1920s, valve sets spread like wildfire and crystal sets were soon forgotten. Peter
To pick up a radio programme on any radio you first must know its frequency and then build a curcuit to match that frequency. IMHO the Americans before they left must have arranged some sort of intelligence network with given frequencies and times of transmission along with a few receivers and code books. The trouble is that the Japanese could also pick up the transmissions and with direction finding equipment find the location of the transmitter and hence distroy or jam it. However, medium and long wave signals can travel long distance with high power and at the right time of the day, depending on the quality and location of both transmitting and receiving aerials. Today there is a Norwegian amateur who can listen to stations from USA on medium wave 147khz from New York(if I remember right). During the occupation of France the BBC transmitted regularly to the French resistance, and inspite of German threats the population still dug out the trusty radio and tuned in to listen. The same could have happened in the Philippines.
Wendy, Why don't you try contacting the Radio Society of Great Britain , the American Radio Relay League at ARRL Home Page , or VMARS-The Vintage and Military Amateur Radio Society ? I'm sure at least one of them will be able to answer your question even more fully.
This is my first posting, so advance apologies if I err. I'm one of perhaps many sons who used to think that, because his father never spoke about his war service, there was nothing of interest to know. A little older and, perhaps, wiser, I have realised that his service in West Africa may have had greater significance than I imagined. I am fairly sure that he was working with land-based high frequency direction finding (a.k.a. "huff-duff"). I believe that the technology made it possible to triangulate the position of u-boats when they surfaced to signal back to base. You wouldn't think this would still be any kind of secret, but a Dutch commentator has written that ' "It even happened that, in the 1960's, after Derek Wellman offered BBC TV a play concerning his experience as a wartime huff-duff operator, a call came advising him that "this subject is not of interest to the British people"!! ' I can find very few British sources on the subject, so comments and suggestions for further research would be appreciated. Paul
It is likely that in South Africa H.F.D.F. was looking for surface ships. German Commerce Raiders were very active in the South Atlantic and Indian Oceans and this would be one of the few ways of tracing them. In the end their downfall was due to the cracking of the Kreigsmarine enigma codes but this of course would have to be disguised as being found by other means. The 'U' Boat activity that far south was supported by supply ships untill these were also found using the same methods. Hope this gives a bit of background. Regards, Ken.
CORRECTION TO POST ABOVE. Sorry meant to say West Africa which would have then covered the shipping routes around Madagascar and central Indian Ocean. An even more important hunting ground for the Raiders.
