Build Basic Radio Frequency Electronic Circuits


Posted on Feb 6, 2014

AM radio receivers receive or demodulate amplitude modulated (AM) signals. The most common source of these signals is of course todays Standard AM Radio Broadcast Band but shortwave stations use AM modulation as well. Amplitude modulation was really developed between 1900 and 1917 by amateur radio experimenters (`hams`). Then when WW1 ended, comme


Build Basic Radio Frequency Electronic Circuits
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rcial AM radio broadcasts began. Amplitude modulation means that the output power of a radio stations transmitter increases or decreases in accordance with the music or voice that is being transmitted. If we string out a length of wire, some of that transmitted energy will cause a small current to flow in our wire. That current will increase and decrease in step with the modulation of the carrier wave and if we hook the wire to a diode detector, the detector will detect or demodulate the signal leaving only the audio. The loop antenna is made out one piece of 1X2 pine lumber 6 feet long. Cut the piece in half so that each section is now 3 feet long. Find the center of each and cut a slot the exact width width of the narrow dimension (3/4") on both sections the cut should extend down half way through the piece on each. Now slide and tap the two sections together to form a "X". You may want to glue the two together. Insert two small wood screws side by side near the center of the "X" on one of the cross arms. This will be the starting and ending points for the wire that is wound around the outside of the "X" forming the main antenna. Now insert two more wood screws on the oposite side of the first two. This will be the starting and ending points for the single turn loop of wire that couples the main loop into the radio. Starting at one of the two side by side screws, wrap the wire around the screw a few times to hold it and...




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