Testing Board 1 - Bandpass Filters || Back to Testing Board 1 - Crystal Filters
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The image above shows the parts needed to prepare the heat shrink tubing for using between the IREDs and the photo devices. The tubing is a little larger than needed and is curved or even bent when taken out of the bag. A screwdriver and a lighter is used to get the diameter of the tubing correct and straightened out. The piece above is used between the Crystal Filter and the Phototransistor between the VFO Amplifiers. It is cut 5" long. The ends are trimmed 1/8" after finishing. The pieces used between the Bandpass filter/VFO and the Crystal Filter/Crystal Oscillator are prepared the same way but are much shorter than the piece above. |
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The best dimension for the screwdriver shaft is 3/16", but anything close will work. Any smooth tubing can be used, it doesn't have to be a screwdriver. |
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The tubing is slipped over the screwdriver and heated in sweeping motions. Do not keep the heat at one place or it will distort the tubing. Feel where the end of the screwdriver is located and do not heat that part of the tubing. The piece will be turned over to get the part that is missed. Leave plenty of room from the end of the screwdriver so the end will not be closed shut from the heat. |
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The tube after the first heating is finished. |
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The tube is turned around and the end that was missed is heated. |
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The tubing after the second heating is finished. It is straight and the exact size to fit over the IRED and Phototransistor. |
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