By Mark Forbes, KC9C PO Box 445 Rocklin, CA 95677

This month, several interesting components, plus a possible suggestion or two you can use for a good Christmas present.

Miniature Fuses

Everything in electronics has been miniaturized as time has progressed... except fuses. Now, Schurter Corporation has come up with a line of fuses which, in the smallest package, are about the size of a 1N914 diode. Each of the fuses bears UL, CSA, VDE and other certifications.

The fuses are available in three voltage ratings: 63 V, 125 V and 250 V. And current ratings are from 63 mA to 15 A, depending on the package.

The packages come in four styles. The most recognizable is a small, PC-board-mount fuse (models MSF and MSA) that is a miniaturized version of the standard glass package that we're all familiar with. The other packages are more "exotic."

Surface-mount fuses are available in two styles to keep pace with ultra-miniature designs. The OMF 63V handles 63 mA to 5 A, and is only 7.4-mm long. The MELF 125V is available in 63-mS to 15-A versions, and measures only 7.3 mm.

The other two packages resemble small electrolytic capacitor packages. The MSF series look just like the capacitor packages, and are available in ratings from 100 mA to 5 A, and have radial leads (so they "stand up" on the pcb). The final package, the PSC 125V, is a four-terminal fuse, roughly resembling a surface-mounted potentiometer. This interesting product also offers integral and remote indication capability so that its 'blown" state can be detected without having to look at the circuit board.

If you are interested in these products, write or call Schurter, PO Box 750158, Petaluma, CA 94975-0158; phone 707 778-6311.


Lemo USA, Inc, has published a new catalog of electronic connectors. This company is fairly new in the market, so most of us are not familiar with it. However, they offer a full line of quality connectors, including RF, fiber optic, cables, high-voltage, and other standard and custom connectors.

Their catalog is available free of charge and is certainly worth having. To get a copy, write or call them at Lemo USA, PO Box 11488, Santa Rosa, CA 95406; phone 800 444-5366.

20 QEX

Sensor Interface IC

Telephonic Corporation has a new IC which accepts low-voltage inputs from sensing devices (such as temperature, voltage and other status devices) and sends a serial data stream to a microprocessor. These could be used in remote or difficult-to-access repeater sites for conversion of telemetry to microprocessor-compatible data. The parts are inexpensive, about $5 for small quantities.

To obtain more detailed information, contact Telephonies Corporation, 815 Broad Hollow Road, Farmingdale, NY 11735; phone 516 755-7000.

EMI Filters

Anyone experiencing EMI from computer products or packet equipment, or generating EMI with their radio products, may be interested in a line of miniature EMI filters from Coilcraft. These come in a variety of packages for various applications.

Packet fans may find the cable filters useful. These are double-ended DB-25 and DB-16 connectors with integrated filters. They provide as much as 19-dB attenuation of RF noise over 30-250 MHz.

Also useful for hams are several telephone filters. The simplest of these is an "RJ-xx" style connector with a built-in filter. These are perfect for calming neighbors who can't understand why you are interfering with their phone that they received free with that magazine subscription!

For EMI help contact Coilcraft, 1102 Silver Lake Road, Cary, IL 60013; phone 800 322-2645.

Circuit Simulation Software

Intusoft has developed several analog and digital circuit simulation programs. These programs allow you to design circuits, then enter the schematics and view the performance parameters graphically without the expense of actually building the circuit. You can then debug or fine tune the circuit in the computer simulation before ever soldering any components together. Most designers today use computer simulation programs to speed up the design and allow "tweaking" before ever constructing the hardware.

These programs are inexpensive enough that any ham might find them a useful addition to his or her test bench. And they might make a nice Christmas present too! Prices start at $95.

To find out more, contact Intusoft, PO Box 710, San Pedro, CA 90733-0710; phone 310 833-0710.

RF Design Book

This would make a great Christmas gift for the ham who experiments with RF circuits. The book, entitled Radio Frequency Transistors: Principles & Applications, is not one of those books that simply provides pages of data sheets with cookbook circuits. This book will actually help you to understand how various active components work and how to design circuits for the exact application you need.

The book discusses selection of solid-state devices for specific applications, bipolar devices vs field effect transistors, general RF power design practices, test and measurement principles, and thermal aspects of RF designs. Also shown are application design examples for: amplifiers, oscillators, switches, pulsed power, power MOSFETs, and even wiring considerations with RF.

The book isn't exactly cheap, but if you want a good tutorial on RF design, it's worth its $49.95 price (plus $3.50 shipping). To order, contact Butterworths, 80 Montvale Avenue, Stoneham, MA 02180, or call 800 336-2665.



Mike Gruber, WA1SVF, notes that his September 1992 QEX article, "Synchronous Detection of AM Signals," didn't make sufficiently clear that the circuit of Fig 7 was designed by Steve Johnston, WD8DAS. QEX regrets this error.


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