The Gunnplexer Cookbook
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I The Gunnplexer Cookbook The Gunnplexer Cookbook A Microwave Primer for RADIO AMATEURS & ELECTRONICS STUDENTS Robert M. Richardson, WPUCH/2 Ham Radio Publishing Group Greenville, New Hampshire 03048 The Gunnplexer Cookbook 01981 Robert M. Richardson Richcraft Engineering Ltd. Drawer 1065 Chautauqua Lake, N. Y. 14722 Library of Congress Number 81-80617 All rights reserved. No part of this book may be reproduced in any way, or by any means, without written permission in writing from the publisher. Printed in the U.S.A. This book is dedicated to those outstanding vhf, uhf, and microwave Amateurs whose many contributions to our hobby, avocation, science, and art have led us to the level of today's Amateur microwave technology. Those outstanding Amateurs, both past and present during the last 30 years include: Ed Tilton-WlHDQ, Denis Heightman-G6DH, Sam Harris-W1 FZJ, Rick Emerson-W3OJU, Tom Blevins-W4UMF, Dana Atchley-WlCF, Clair Sutton-W8CMS, Ross Bateman-W4A0, Fred Collins-WlFC, Grid Gridley-W4GJ0, Ralph Thomas-KHbUK, John Chambers-WbNLZ, and Bob Cooper-KbEDX/W5KHT, to name a few of the leaders. Exceptional contributions to 10-GHz Amateur techniques have been made by many of our British cousins who pioneered early Gunn-diode experiments and applications. A special thank-you is due D. S. Evans- G3RPE and G. R. Jessop-GbJP, the editors of the RSGB VHF-UHF Manual, and those British Amateurs who contributed to the microwave section of the RSGM VHF-UHF Manual. Contents 1 Basic Gunn Diode Theory................................................. 1 A description of negative-resistance microwave devices, Gunn diode fabrication, Gunn diode mounting and tuning, Gunnplexer mixer and isolator, and Gunn oscillator spectral noise 2 Gunnplexer Operation .....................................................11 10-GHz propagation, path loss, range vs i-f bandwidth, and carrier-to-noise ratio. Also discusses Gunn diode cavity tuning and Gunnplexer antenna basics 3 Frequency and Power Measurements .................................2 1 Construction of a simple micrometer-driven frequency- measurement table and 10-GHz relative power output di- pole/diode attachment. 4 Power Supplies ...............................................................33 Assembly of Gunnplexer power supplies including single 12-Vdc storage battery driven systems to dual-regulated ac to 12-Vdc to 10-Vdc units. Proportional Temperature Control .....................................45 Low cost proportional temperature control system for the Gunn- plexer that maintains 0.1%F to 0.01%F control of the Gunnplexer module from 32 to 90 degrees F ambient. I-f Amplifiers .................................................................6 1 Presents two low-noise i-f preamplifiers that are mounted on the Gunnplexer module. Weatherproof Enclosure and Tripod/Rotator Mount ............7 1 Details of an economical weather-proof Gunnplexer enclosure and tripod mount. Automatic Frequency Control ...........................................87 Discusses the use of the LM3900 operational amplifier as a Gunnplexer AFC amplifier. Level-I Communications System .......................................97 Describes three approaches for using low-cost fm broadcast radios as tunable i-f receivers and AFC sources. 10-GHZ Weak-Signal Source ............................................127 Outlines construction of a 10-GHz weak-signal source using a 432-MHz transmitter kit. plus combination crystal multiplier/lO- GHz antenna and coaxial mount. Parabolic Reflector and Gunnplexer Mount ........................145 The assembly of a 25-inch-diameter parabolic reflector made from a Sno-Sled dish, Gunnplexer and tripod/mast mounts. Phase-Locked Gunnplexer System .....................................185 Phase locking the Gunnplexer diode to a harmonic of a 19-MHz crystal oscillator - Crystalmatic system. 13 Level-I1 Communications System ......................................203 Description of a complete narrowband phase-locked Gunnplexer system. 14 Narrowband Gunnplexer Techniques................................. 245 Details construction, tuning, and test of the Level-I1 communica- tions system as well as narrow bandwidth (400-1000 Hz) CW and FSK communications techniques. 15 Television and Computer Data Links .................................279 Construction details of video i-f amplifier, Wheatstone bridge dis- criminator, AFC amplifier, video amplifier, TV modulator, and SAW filter for vestigial sideband TV output. 16 Epilogue .........................................................................321 Slope detecting Gunnplexer fm video output on a standard U.S. a-m (video) television receiver. Surprisingly, fm/fm video/audio without conversion, will give studio quality picture and sound. Receive 7+ channels with a single Gunnplexer. Index 333 Foreword The Gunnplexer Cookbook is written for the vhf/uhf radio amateur or electronics student who has at least modest experience assem- bling vhf converter or receiver kits. The only test equipment required is a grid-dip meter, VTVM or multimeter, a standard broadcast fm receiver, an ordinary TV set, and a good quality high-frequency communications receiver that covers 400 kHz to 30 MHz. It is much easier to design and build a high-gain video i-f if you have access to a sweep generator and oscilloscope for final alignment. Most amateurs, however, do not have this test equip- ment available; therefore, the video i-f stages presented in Chapter 15 may be aligned using only a grid-dip oscillator and an fm broadcast receiver. An additional caveat is that, for the same reasons, no machining of the original Gunnplexer/horn antenna module will be necessary. I have tried to present the subjects in such a way that an isolated vhf/uhf enthusiast, working alone, without help, can build the modules described. At the same time I have tried not to overburden the microwave old-timer who built his first 10-GHz polaplexer transceiver 25 years ago. The line between too much and too little detail is difficult to tread; the reader is asked to be forgiving when the line is too much one way or the other. Preface PROPHETS - PIONEERS - PORTENTS "To predict the future, one must first understand the past." The evolution and development of microwave communications, its history per se, is one of the least understood and misconstrued subjects in the lexicon of the average E.E. student and Radio Amateur today. First off, let's try to clarify some of the more popular misconceptions. Guglielmo Marconi's first major contribution to communica- tions technology was his demonstration of long-wave two-way communications across the North Atlantic in 1901. WRONG:In 1897 Marconi demonstrated a 1.2-GHz microwave link to the British Post Office. His modulated spark-gap power source covered a 4-mile path and used a Branley-Lodge coherer for the detector. Longwire antennas and shielded (coaxial) transmission lines preceded parabolic reflectors and waveguide by approximately 30 years. WRONG : Oliver Lodge demonstrated waveguides to the Royal Institute in London in 1894 and also demonstrated waveguide polarization by rotating the detector 90 degrees. Professor Au- gusto Righi, Marconi's principal teacher in Italy, developed both parabolic reflectors and refracting microwave lenses during the late 1890s. Heinrich Hertz, even earlier, circa 1888, used a parabolic mirror for focusing 420-MHz spark-gap generated rf energy on a nearby dipole antenna with a spark-gap detector. The first commercial microwave telecommunications link was established between New York City and Boston shortly after World War 11. WRONG: ITT's European R&D houses, LCT (France) and STL (England), established a 1.75-GHz microwave link across the English Channel in 1933 using 33-dB gain parabolic reflector antennas at each end. Though stoutly denied, it is rumored to still be in use today. The magnetron was invented by Randall and Boot in En- gland during February 1940. WRONG: The magnetron was invented by Albert Hull in 1921 at the General Electric Research Labs in Schenectady, N.Y. This smooth-bore magnetron was originally invented by Hull as a low- frequency, magnetically controlled amplifier to circumvent the extensive patent litigation, at the time, between DeForest, West- inghouse, and General Electric. In due course, the triode vacuum tube patent problems were resolved, but Hull continued magne- tron development through 1925, by which time he was developing over 8 kilowatts power output in the audio and ultrasonic frequency range. Thereafter, the magnetron was virtually forgot- ten until Randall and Boot invented the cavity magnetron in 1940, which in itself was a spectacular achievement. After Marconi's historic trans-oceanic communications feat in 1901, he devoted the rest of his life (died 1937), developing long-, medium-, and short-wave communications systems. WRONG: In an address before the Institute of Radio Engineers in 1922, he stated: "The study of very short electric waves (microwave), although sadly neglected practically all through the I history of wireless, is still likely to develop in many unexpected directions and open up new fields of profitable research." Mar- 1 coni, indomitable genius that he was, then went on to discover 1 microwave troposcatter using his own 3-GHz communication system in 1934. I So much for the anomalies of microwave history and the many popular misconceptions that exist to this day. As the Gunnplexer Cookbook is not a history of microwave technology, we'll skip the very significant contributions