Experiment with the circuit – you can “short out” coil turns with the paper clip tuning tap better yet, you can just connect the tap to the razor blade/earphone circuit instead, a more common configuration. This served to “build up” the antenna signal to a level that could be heard in the earphones by a process known as “detection”.Īn attached coil of enamel-insulated wire wound on a piece of bamboo acted along with the antenna wire capacitance to produce a tuned circuit, tuned approximately to the radio frequency band of interest. This served the purpose of the “crystal” and “cats whisker” of early crystal radios it permitted current coming in from the antenna to flow in only one direction. These were the “Blue Blade” type that had a blue oxide finish, and that finish, in contact with an ordinary pencil “lead”, made a point-contact rectifier. I built the Fox Hole Radio described below after a friend produced a WWII Red Cross package containing razor blades among other common items. The omnipresent Ham Radio operators in the Signal Corps probably helped, applying their skills of the day. This was early 20th century technology and any self-respecting GI was up on it. I’m not interested in those things, but I digress). They were the equivalent of today’s techno-geeks and computer hackers (but not the modern kid who thinks “communications technology” is poking their finger at the screen of a Chinese-made iPhone.
Heathkit cr 1 crystal radio how to#
The radios were built by the young GI’s who just knew how to make such things. That perforated Messerschmidt or Betty could also be a source for the necessary wire for the antenna tuning coil and antenna. The radio could be built from basic scrap, with the exception of the earplug or earphones those could be liberated from that enemy tank or aircraft wreckage. They were built and used during the time spent in the “Wait” part of “Hurry up and Wait”. These Fox Hole radios did not require batteries – they were powered by the signal from the distant radio station as collected by the receiver antenna. The BBC, Radio Australia and US Armed Forces Radio Stations would carry news from home, music and the all-important sports scores. Although the enemy propaganda was laughable, those stations attracted GI’s with their popular music pumped out by powerful radio transmitters. “ If it’s stupid – but works – it isn’t stupid “ Murphy’s Laws of Combatĭuring WWI, WWII and later conflicts, many GI’s built “Fox Hole Radios” to listen to news, music, Tokyo Rose, Axis Sally, Lord Haw Haw and probably Hanoi Hannah too. I’ve built a lot of crystal radios but this one still works the best due to careful antenna – diode – headset impedance matching. A crystal radio would have been very handy at that point.įun times – I still have the CR-1 and it still works great although the H-43/U headset shown above is not original. The transmitting sites would change every several minutes as they broadcast emergency information messages. Measures taken by the USG to prevent Soviet bombers from homing in on our AM broadcast transmitters as the Imperial Japanese Navy did during the attack on Pearl Harbor. These markings were required on all radio receivers built between 19, including this one. Those little CD (Civil Defense) markings were the frequencies set aside (6 KC) in the AM broadcast band for CONELRAD alert messages. Note the markings on the right-hand “DET” dial. Wrong….(I learned after looking through a Heathkit catalog that that feat would require a radio TRANSMITTER! I would drool over actual transmitters in the catalog that could do this – like the DX-100 which I would eventually own).