QEX (ISSN: 0886-8093 USPS 011-424) is published monthly by the American Radio Relay League, Newington, CT USA.
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David Sumner, K1ZZ
Jon Bloom, KE3Z
Lori Weinberg Assistant Editor Harold Price, NK6K Zack Lau, KH6CP Contributing Editors
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Joe Costa Technical Illustrator
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Copyright © 1994 by the American Radio Relay League Inc. Material may be excerpted from QEX without prior permission provided that the original contributor is credited, and QEX is identified as the source.
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October 1994 1
The American Radio Relay League, inc, is a noncommercial association of radio amateurs, organized for the promotion of interests in Amateur Radio communication and experimentation, for the establishment of networks to provide communications in the event of disasters or other emergencies, for the advancement of radio art and of the public welfare, for the representation of the radio amateur in legislative matters, and for the maintenance of fraternalism and a high standard of conduct.
ARRL is an incorporated association without capital stock chartered under the laws of the state of Connecticut, and is an exempt organization under Section 501(c)(3) of the Internal Revenue Code of 1986, Its affairs are governed by a Board of Directors, whose voting members are elected every two years by the general membership. The officers are elected or appointed by the Directors. The League is noncommercial, and no one who could gain financially from the shaping of its affairs is eligible for membership on its Board.
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Executive Vice President: DAVID SUMNER, K1ZZ Purpose of QEX:
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Previously in this space we have decried the lack of low-cost design and development tools for amateurs. While multi-thousand dollar tools abound, they are hardly accessible to the amateur in the street, so to speak.
Well, cheer up. ARRL has taken the initiative to address this problem in one area: RF circuitry. Working with Compact Software, of Paterson, NJ, ARRL will soon make available ARRL Radio Designer. This Windows program performs linear analysis of circuits. That may at first sound like a description of PSPICE, or MicroCAP, both of which are linear circuit simulation tools available at low cost (in their simpler versions, that is I, but ARRL Radio Designer is different. What makes it different is that it really does RF, although it will do low-frequency circuits, too.
One of the frustrating problems with trying to use SPICE-type simulators at RF is that they don't speak the language. S-parameters, Y-parameters, H-parameters, group delay, reflection coefficient, VSWR, return loss, noise parameters—these are part of the lingua franca of both ARRL Radio Designer and human radio designers.
And ARRL Radio Designer includes capabilities usually found only in high-end programs. Want to optimize your preamp design for noise figure? Let ARRL Radio Designer's optimizer find the best set of input matching circuit components to do the job— than ask it what the resulting input VSWR will be. Want to know if you really need 1% resistors in that critical part of the club-project circuit you've designed? ARRL Radio Designer's statistical processing can tell you how many of the club's copies of the circuit will be unstable if you use 5% components.
There are limitations, of course. As a linear circuit simulator, ARRL Radio Designer can't provide information about distortion products or large-signal operation of circuits. But it can help you design and optimize the linear circuits used in your RF designs. Most of the circuits in a radio system are linear, after all. And, as KA2WEU shows us this month, ARRL Radio Designer can sometimes assist in designing even a large-signal circuit such as an oscillator.
ARRL Radio Designer's reports are available in both graphical and tabular form, as part of its Windows user interface. That means you can see the results on the screen right away, and you can print the resulting graphs or tables of calculated values.
You can read more about ARRL Radio Designer, including some sample applications, in "Introducing ARRL Radio Designer: New Software for RF Circuit Simulation and Analysis," October, 1994, QST.
Low phase noise is the holy grail of 1990s radio design. To achieve it, you need to be "Designing Low-Phase-Noise Oscillators." Dr. Ulrich L. Robde, KA2WEU, discusses the design procedure and shows how modern computer circuit simulation tools simplify the problem tremendously.
Part 2 of "Practical Microwave Antennas," by Paul Wade, N1BWT, covers dish antennas—how to build them and feed them.
Need an "Inexpensive PC A-to-D" capability? Gary C. Sutcliffe, W9XT, shows how the PC's game port can serve as a simple way of measuring an external resistance, such as a thermistor.
In this month's "Digital Communications" column, Harold Price, NK6K, expands on his previous discussion of what's holding back amateur packet development.
This month we begin a new column: "Proceedings," As the various amateur technical conferences take place, we will print lists of the papers available in the conference proceedings. Our hope is that this will help you locate those papers that can help you with your experimental efforts.— KE3Z, email: [email protected] (Internet)
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