Published:2009/6/26 3:01:00 Author:Jessie
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Published:2009/6/26 2:59:00 Author:Jessie
Single meter scale covers 1-1000W, with equally spaced divisions for 1,10,100,and 1000. This log scale makes it possible to measure very low reflected powers and very high forward powers simultaneously with same percentage accuracy.
Basis of operation is that voltage dropped across forward-biased 1N40C2 silicon PN junction diode is proportional to logarithm of cur rent through it. For 50-ohm line, use 220 for R2 and 27 for R3 and R4. For 75 ohm Iine, coffesponding values are 180 and 33. Detectordiodes are point-contact germanium rated at 80 PIV.
Article gives construction details. Ground coax braid at one end only. Ferrite ring is 0.5-inch Mullard FX1596 or equivalent.-P.G.Martin, Some Directional Wattmeters and a Novel SWR Meter, 73Magazine,Aug.1974,p 17,19-21,23-24,and 26. (View)
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Published:2009/6/26 2:57:00 Author:Jessie
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Published:2009/6/26 2:51:00 Author:Jessie
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Published:2009/6/26 2:43:00 Author:Jessie
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Published:2009/6/26 2:40:00 Author:Jessie
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Published:2009/6/26 2:37:00 Author:Jessie
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Published:2009/6/26 2:35:00 Author:Jessie
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Published:2009/6/26 2:31:00 Author:Jessie
Used with communication receiver to measure impedance at antenna terminals or at end of transmission line, as required for adjusting antenna matching and loading devices for desired impedance at specific frequency. Consists of diode.connected transistor broadband,noise generator, 3-stage noise amplifier, and toroid transformer bridge.
All transistors are 2N5129 or equivalent 2N5137 or 2N5220. Try different transistors until highest noise output is obtained. Toroid core for trans.former is 3/8-inch Indiana General CF102. Quadrifilar winding has 4 1/2 turns of four No.28 enamel wires twisted together, wound on core and connected as on diagram. Noise bridge can also serve as wideband noise source for signal injection during troubleshooting in AF or RF circults, and as noise source for aligning RF cir-cuits,-J.J. Schultz, An Improved Antenna Noise Bridge, CQ, Sept, 1976, p 27-29 and 75. (View)
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Published:2009/6/26 2:59:00 Author:May
Single meter scale covers 1-1000W, with equally spaced divisions for 1,10,100,and 1000. This log scale makes it possible to measure very low reflected powers and very high forward powers simultaneously with same percentage accuracy.
Basis of operation is that voltage dropped across forward-biased 1N40C2 silicon PN junction diode is proportional to logarithm of cur rent through it. For 50-ohm line, use 220 for R2 and 27 for R3 and R4. For 75 ohm Iine, coffesponding values are 180 and 33. Detectordiodes are point-contact germanium rated at 80 PIV.
Article gives construction details. Ground coax braid at one end only. Ferrite ring is 0.5-inch Mullard FX1596 or equivalent.-P.G.Martin, Some Directional Wattmeters and a Novel SWR Meter, 73Magazine,Aug.1974,p 17,19-21,23-24,and 26. (View)
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Published:2009/6/26 2:57:00 Author:May
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Published:2009/6/26 2:51:00 Author:May
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Published:2009/6/26 2:43:00 Author:May
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Published:2009/6/26 2:40:00 Author:May
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Published:2009/6/26 2:37:00 Author:May
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Published:2009/6/26 2:35:00 Author:May
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Published:2009/6/26 2:31:00 Author:May
Used with communication receiver to measure impedance at antenna terminals or at end of transmission line, as required for adjusting antenna matching and loading devices for desired impedance at specific frequency. Consists of diode.connected transistor broadband,noise generator, 3-stage noise amplifier, and toroid transformer bridge.
All transistors are 2N5129 or equivalent 2N5137 or 2N5220. Try different transistors until highest noise output is obtained. Toroid core for trans.former is 3/8-inch Indiana General CF102. Quadrifilar winding has 4 1/2 turns of four No.28 enamel wires twisted together, wound on core and connected as on diagram. Noise bridge can also serve as wideband noise source for signal injection during troubleshooting in AF or RF circults, and as noise source for aligning RF cir-cuits,-J.J. Schultz, An Improved Antenna Noise Bridge, CQ, Sept, 1976, p 27-29 and 75. (View)
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Published:2009/6/26 2:31:00 Author:May
Cornbination of short whip antenna and broadband amplifier gives antenna covering entire range of 3 to 30 MHz without frequency selectivity. at is 2N3819 FET source follower driving three-transistor amplifier using 2N918, 2N6008, or other 200-MHz 20V NPN transistors to provide 30-dB gain. Circuit rolloff starts at 3 and 35 MHz. High gain of am plifier makes combination simulate quarter-wave whip over entire frequency range.-R. C.Wilson, The Incredible 18 All-Band Antenna, 73 Magazine, March 1975, p 49-50. (View)
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Published:2009/6/26 2:30:00 Author:May
Ferrite-rod antenna is combined with 16-inch wire rod to give cardioid radiation pattern for low-noise 160-meter antenna system. Preamp using MPF102 FETs has gain of 25 dB. L1 is 48 turns No.14 enamel spread to 4.5 inches on 0.5 inch Amidon ferrite rod 7 inches long. L2 is 6-turn link wound over center of L1.L4 and L5 are each 50 turns No.26 enamel on 780-2 powdered-iron toroid cores, with 6 turns for links L3 and L6.-D. DeMaw, Low-Noise Receiving An-tennas, QST, Dee.1977, p 36-39. (View)
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Published:2009/6/26 2:29:00 Author:May
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