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DIGEST OF ARTICLES - QST March, 1994 Following are digests of articles printed in the March, 1994 issue of QST. Such digests are being prepared for each issue of QST, and posted periodically. Subsequent issues will be posted one per week until they "catch up" to the current date in mid-1994, thereafter monthly. It is hoped that other hams will volunteer to post similar digests of the other ham technical publications such as QEX, CQ, 73, COMMUNICATIONS QUARTERLY, RTTY JOURNAL, et al. Especially desirable would be digests of publications in other countries, such as the RSGB RADIO COMMUNICA- TIONS and ham magazines in Europe, Japan, Australia, and other countries around the world. We English speakers would especially enjoy them if they were translated into our language, but they would also be valuable additions to the world's knowledge if they were posted in the language of origin. Who knows? Some bi-lingual ham somewhere might translate them into English and re-post them. Worldwide communications are getting better and better. The time has come to make the world's ham press available to all hams throughout the world! The major value of digests is to give readers sufficient information to decide whether to obtain a copy of the full text. If any U.S. reader wants a copy of an article in QST, please inquire of other hams in your own neighborhood. Many have collections of back issues. Anyone who is unsuccessful in finding a fellow ham with a collection should try every library in the area, especially those at universities and technical colleges. If all else fails, a copy can be obtained from the ARRL Technical Department, 225 Main St., Newington, CT 06111-1494 USA for a fee of $3.00 per copy. Remember, it is both cheaper and quicker to obtain one locally. Readers in most other countries can obtain copies from their own national ham organizations, sometimes translated into their own languages. -------------------------------CUT HERE--------------------------------- COPYRIGHT NOTICE: Copyright to all the following material from QST Magazine is held by the American Radio Relay League (ARRL), effective on the date of issue. Permission is granted for redistribution of the following in its entirety, or in part, provided that this copyright notice is not removed or altered and that proper attribution is made to ARRL as publisher of QST, to the authors of the original articles, and to W. E. "Van" Van Horne, W8UOF, author of this compilation. _________ TABLE OF CONTENTS (line number in parentheses - counting from CUT HERE line) TECHNICAL ARTICLES (TA) TA1:A Lead-Acid Battery Charger 74 TA2:The Pfeiffer Quad Antenna System 116 TA3:Using a VU Meter for Phone-Patch Adjustment 222 TA4:On Center-Fed Multiband Dipoles 273 TA5:Under the Hood IV: Inductors 332 PRODUCT REVIEW (PR) PR1:QST Compares: Dual-Band Hand-Held FM Transceivers 363 PR2:Trimble Scout GPS Hand-held Global Positioning System Receiver 544 HINTS AND KINKS (HK) HK1:Cleaning Up the Beep Tone in the TEN-TEC Omni V Transceiver 598 HK2:Simple Audio Attenuator Solves TNC Overload Problems 613 HK3:Stopping Bug and Paddle Skids 634 HK4:Is That Hardware Stainless? 642 TECHNICAL CORRESPONDENCE (TC) TC1:Maximum Bandwidth Monopole Antennas 660 TC2:Toroidal-Core Color Codes 708 LAB NOTES (LN) LN1:TVI, CATVI, and VCRI 732 NEW HAM COMPANION (NHC) NHC1:Worked All Palm Beach 769 NHC2:Getting Started on the Magic Band 800 NHC3:The Doctor is IN 825 NHC4:PACSATs from an Apartment 838 NHC5:Plug into PacTOR 853 NHC6:An Over-the-Dash H-T Mount 864 RADIO TIPS (RT) RT1:Activity Nights 893 RT2:Operating on the Road 930 GENERAL INTEREST ARTICLES (GI) GI1:Amateur Radio Direction Finding in China 954 GI2:Radio Gear of Yesteryear 971 GI3:A New Outlook on Ham Radio 1008 GI4:Being an Elmer 1023 GI5:Anatomy of a 10-GHz Record 1037 GI6:Cellular Radio and the Modern Amateur 1052 GI7:Wally and Mike: Changing Times 1071 ------------------------------------------------------------------------ TECHNICAL ARTICLES (TA) Title>TA1:A Lead-Acid Battery Charger Author>Spencer, Ben C. - G4YNM Source>QST Mar 94, pp. 25-27 Abstract>Construction of a charger for sealed lead-acid batteries. Its circuitry assures safe charging and automatic shut-off when full charge is reached. Digest>This article describes the construction of a charger, specifically designed to charge the sealed lead-acid batteries of the type used in burglar alarms, older portable telephones, and other kinds of equipment. Often they are found for sale in hamfest flea-markets. Charging such batteries requires that the charging voltage must not exceed 2.45 volts per cell, the maximum charge rate must not exceed 15-percent of the battery's ampere-hour rating, and the battery must not be overcharged. The circuitry of this charger is designed to assure that all three limits will not be exceeded. A schematic diagram is included in the article. The circuit shows a transformer that operates from 120-volt a.c., with an 18-volt secondary. A voltage regulator drops the output to 1.2- to 14.75-volts. The sensing circuit illuminates a green LED to show when the charger is switched on and ready to charge or charging current is flowing. When a partially-discharged battery is attached to the charging terminals, the red light goes out and a green light comes on, indicating charging. When the battery reaches 90-percent of full charge, the green light goes off, the red light again comes on, the output voltage drops to a low level, and current stops flowing. Protective diodes prevent reverse current flow. Two different charging rates, 1-amp and 3-amps, are provided and selected by a two-position switch, labeled "Standard" and "Rapid". A PC-board, etched and drilled for this project, is available from FAR Circuits, 18N640 Field Court, Dundee, IL 60118-9269 for a price of $6.00, including USA shipping. A template is available from the ARRL for an SASE. Address the request for Spencer Battery-Charger Template to the Technical Department Secretary, ARRL, 225 Main St., Newington, CT 06111. _________ Title>TA2:The Pfeiffer Quad-Antenna System Author>Pfeiffer, Andy - K1KLO Source>QST Mar 94, pp. 28-31 Abstract>Construction and performance of miniaturized quad beam antennas comprised of two shortened elements made of wire using linear loading. The size of each element is reduced 45% from that of a full-size quad in one type antenna described, and 58% in the second type. Performance of either is reported equivalent to that of a full-size quad. Digest>Mr. Pfeiffer has developed miniaturized quad antennas using linear loading techniques. He has settled on two configurations which he calls the "Maltese Quad" and the "Maltese Double-Cross Quad". The Maltese Cross is the familiar one that was used as identification by the German air force in World War I. The arms of the cross get broader at their ends, so that it looks somewhat like a square with slots cut out from each corner toward the center. Each element of the author's Maltese Quad uses crossed spreaders, in the conventional quad manner, and wires around the periphery; but at each tip a closed-end stub is inserted that runs down the spreader toward the hub. The two sides of the stub add enough wire that full-wave resonance is reached with much smaller spreaders than those required by a full-size, full-wave square. Whereas a full-size 12-meter antenna requires spreaders to be 14-feet, 2-inches (4.32-meters), measured diagonally corner-to-corner, spreaders for the Maltese Quad for the same band are only 8-feet (2.44-meters), measured in the same manner. The stubs are supported by what the author calls "yard-arms". These are short pieces of rod fastened perpendicular to each spreader, one at the tip and the other close to the hub. The outer yard-arm must, of course, be an insulator and is made of fiberglass-reinforced plastic (frp). The inner one acts as a shorting bar that forms the shorted end of the stub. With the Maltese Double-Cross Quad, the author has used the same idea once more; instead of two crossed spreaders, he uses four. The peripheral wires now form an octagon, rather than a square. Again, a stub runs along each spreader with the shorted end not far from the hub and the open end at the tip of the spreader where the wires are attached to the adjacent peripheral wires. Now the reduction in size is even greater. For a conventional 20-meter quad driven element, the diagonal dimension is 25-feet (7.62-meters). Each diagonal across the Maltese Double-Cross Quad is only 10-feet, 4-inches (3.15-meters)! The article contains a dimensioned drawing labeled as follows: S - Spreader length from hub to tip L - Each segment of the peripheral wire, from spreader tip to spreader tip, less the width of the stub X - The length of the stub Y - 1/2 the width of the stub Z - The distance from the center of the hub to the shorting bar, or closed end, of the stub. Dimensions for the 12-meter Maltese Quad are: S = 48-inches (1.22-meters) L = 61-inches (1.55-meters) X = 36-inches (0.91-meters) Y = 5-1/2-inches (14.0-cm.) Z = 12-inches (30.5-cm.) Dimensions for the 20-meter Maltese Double-Cross Quad are: S = 62-inches (1.57-meters) L = 42-1/2-inches (1.08-meters) X = 47-1/8-inches (1.12-meters) Y = 3-inches (7.6-cm.) Z = 15-inches (38.1-cm.) Mr. Pfeiffer recommends that each element be roughly tuned by itself. To tune the reflector, he used formulas found in the CUBICAL QUAD HANDBOOK, by W. Orr, published by Radio Publications, Inc. It contains the following formulas for calculating the dimensions of an 2-element monoband quad, as follows: Perimeter, Driven Element: 1000/f Perimeter, Reflector Element: 1032/f Element Spacing: 118/f >From this, he noted that for any given frequency, the reflector in a conventional quad must be 3.2-percent longer than the driven element. If the driven element resonates, standing alone, at a particular frequency, the reflector must resonate at 96.90-percent of that frequency. Consequently, he tunes the driven element to the target frequency and the reflector to the frequency correspondingly lower. After both elements are mounted, he tunes the array by adjusting the driven element to establish proper resonance frequency and the reflector to maximize either forward gain or front-to-back ratio, whichever is desired. He orients the elements with one corner pointing downward and uses that corner for his feed point. The quads are fed using a gamma-match with the gamma-rod running parallel with, and close to, one wire of the stub. A copper strap shorting-bar is adjustable along the length of both rod and stub. An air-spaced variable capacitor connects between the feed-line and the gamma-rod. It and the shorting bar are adjusted alternately to establish minimum SWR in the conventional manner. The author has systematically evaluated performance of his antennas in cooperation with a friend, Joe Belson - K2ANR, whose QTH is within 60-miles (97-kilometers). K2ANR uses a full-size quad and the two of them have performed many tests comparing the signal-strengths of their signals in various directions, distances, and frequencies, at different times. They both agree that their signals at remote locations are essentially equal, even though Mr. Belson's full-size quad is at a somewhat higher elevation than Mr. Pfeiffer's. _________ Title>TA3:Using a VU Meter for Phone-Patch Adjustment Author>Lorona, Alfred - W6WQC Source>QST Mar 94, pp. 32-33 Abstract>Signal level into a phone-patch is critical and should be adjusted carefully. Described is the use of a VU Meter to set the gain properly. Digest>A phone-patch should be adjusted to deliver a signal into the telephone line that is strong enough to be easily understood but not exceeding the maximum allowable signal level. The best way to adjust to that level is with the use of a VU Meter. This is a special-purpose meter designed to indicate a reasonably accurate value for the peaks of a rapidly-varying voice signal. This requires careful attention to the meter's ballistics; that is, how rapidly it responds to changing levels, and how far it overshoots, if at all. VU Meters are designed and built for this purpose. They are frequently available at hamfest flea-markets and from dealers in electronic surplus. A VU Meter must be used with a 3900-ohm series resistor in order to perform its proper function. The maximum signal level allowed by the telephone standard is 1.228-volts RMS with a 1-KHz. sinusoidal signal. This is equivalent to minus 9-dBm. or about 0.13-milliwatts. A standard VU Meter cannot be used, by itself, to measure that amount of signal accurately because it appears so low on the scale that the accuracy is not good. The signal should be amplified by 13-dB. in order to drive the meter upscale into its high-accuracy range. The article contains a schematic diagram of an op-amp to provide the proper amount of amplification, using a commonly available 741, or similar, op-amp IC. With this amplifier, the VU Meter will indicate 0-dBm. when the signal is actually the desired minus 9-dBm. With the op-amp driving a VU-Meter, and the patch attached to the phone line, connect the input terminals across the telephone and speak the following sentences twice into the phone: "Joe took father's shoe bench out." and "She was waiting at my lawn." Adjust the gain until the meter indicates 0-dB. as the average of the three highest peaks spoken while those two sentences are read twice. Ignore occasional extreme peaks. The sentences are selected to contain all of the fundamental sounds of the English language. The author recommends that, before anyone attaches a phone-patch to their telephone line, they should consult the ARRL Handbook regarding phone-patches, and also obtain a copy of FCC Part 68, from the Government Printing Office, and read sub-part D. _________ Title>TA4:On Center-Fed Multiband Dipoles Author>Belrose, John S. - VE2CV and Bouliane, Peter - VE3KLO Source>QST Mar 94, pp. 34-36 Abstract>Results of a study show that a horizontal dipole fed with tuned feeders is the most versatile amateur antenna. Digest>Since the availability of the WARC bands, amateurs now have eight bands available between 3.5- and 30-MHz. and the use of multi-band antennas has become even more popular than before. A simple dipole, fed with tuned, open-wire feeders is, arguably, the most versatile antenna of all. It can be made of any length but, for good performance on the lowest frequency, i.e. 3.5-MHz., it should not be less than about 100-feet (30-meters) long. A very popular version is one first specified by Louis Varney, G5RV. It is a 102-foot (31-meters) flat-top, fed with 450- to 600-ohm balanced open-wire line or, in a second version, with a 34-foot (10.4-meter) open-wire stub fed at the bottom end with 72-ohm twinlead or coax cable. In his first published description, G5RV called the stub a "matching section", but later decided that he had made a mistake in doing so. Actually, it acts as a matching section only on the 20-meter band. The authors have analyzed many variations of center-fed dipoles, both flat-top and also "inverted vees", with special attention to the G5RV design. In addition, they physically tested a G5RV antenna with a stub, erected as an "inverted vee". The article contains computer plots of the resistance, the reactance, and the SWR across the entire frequency range from 3.0- to 30-MHz. It shows that the flat-top is naturally resonant at 3.49-, 7.52-, 14.15-, 19.5-, and 24.6-MHz. The plots show the very wide range of resistance, reactance, and SWR shown by the antenna at the various frequencies. The stub clearly performs no useful function. They recommend that tuned, open-wire feeders be used all the way from the antenna tuner, located at a convenient place, to the center of the antenna. On the higher frequencies, the antenna becomes more than one half-wavelength long and the radiation pattern breaks up into multiple lobes in various directions. If the wire is horizontal, all of these lobes are radiated at the same elevation angle; but if the ends droop, in an "inverted vee" configuration, that is no longer true. Some lobes will radiate at relatively low angles and others only at high angles. Consequently, the authors recommend that, for use on higher frequencies, it be mounted horizontally. Their final conclusions are that the center-fed dipole, mounted as high as possible and as nearly horizontal, fed with tuned feeders, is the most versatile, as well as one of the simplest, of all multiband antennas. However, they also point out that when an antenna is operating on a frequency at which its length is considerably greater than a half wavelength, the radiation breaks up into a number of lobes with nulls at certain azimuth angles. This means that there are some directions, on certain bands, in which the radiated signal cannot be heard! This, then, is no longer a general-coverage antenna. They suggest that, for frequencies higher than 10-MHz., a better general-coverage multiband antenna is a horizontal loop. _________ Title>TA5:Under the Hood IV: Inductors Author>Bergeron, Bryan - NU1N Source>QST Mar 94, pp. 37-40 Abstract>A primer on inductance and inductors. Digest>This article is an elementary discussion of inductors and inductance. The author describes what they are, how they work, what they do, and the various types that are used in radio. After inductors, he leads into transformers. Accompanying the article are photographs of typical inductors found in radio apparatus. Included are r.f. chokes; toroidal cores, with and without windings; air wound coils; roller inductors; power transformers; audio transformers; and i.f. transformers. Mr. Bergeron explains inductive reactance and its effect on electric current; also parasitic shunt capacitance, internal resistance, and the concept of Q. In a side-bar, three types of variable inductors are described: a coil with a core that can be adjusted in-and-out, a tapped coil with the taps selected by a multi-position switch, and a roller-inductor. Finally, the color code used for encapsulated r.f. chokes is explained. ------------------------------------------------------------------------ PRODUCT REVIEW (PR) Conductor: Mark Wilson - AA2Z Editor, QST _________ Title>PR1:QST Compares: Dual-Band Hand-Held FM Transceivers Author>Ford, Steve - WB8IMY Source>QST Mar 94, pp. 71-76 Abstract>Performance comparisons of five dual-band FM hand-held transceivers: Alinco DJ-580T, ICOM IC-W21AT, Kenwood TH-78A, Standard C558A, and Yaesu FT-530. Digest>For FM operations through repeaters, and for short-range simplex, the 2-meter band and the 70-cm. band are nearly equally popular. Dual-band rigs cover both. In this article, Mr. Ford reviews five models: Alinco DJ-580T, ICOM IC-W21AT, Kenwood TH-78A, Standard C558A, and Yaesu FT-530. All five of the units tested have a number of functions in common. Among these are: band, memory, and program scan; simultaneous dual-band receive; automatic power off; crossband repeater function; CTCSS function; DTMF paging. All transmit a maximum of 2- or 2.5-watts, using the standard battery. All are approximately the same size and four of the five weigh between 13 and 14.4 ounces, battery included; only the Yaesu model deviates a bit, weighing 18.5 ounces. Alinco DJ-580T This unit has the lowest list price of any of the five: $519. The average selling price among several QST advertisers is $409. The reviewer found that programming is somewhat difficult and requires frequent consultation of the instruction manual. But the manual is poorly written; its English is poor, and some descriptions are not complete. When used as a cross-band repeater, some reviewers found that they had to use the low-power output setting on 70-cms. to avoid causing interference on the 2-meter receiver. The unit offers extended receive coverage, including the upper part of the aircraft band. A simple modification, described by the manual, allows full aircraft band coverage. The unit offers 20 memory channels per band, and eight different scanning functions are supplied. One can scan both bands simultaneously; scan the memory channels; scan within preset frequency limits; etc. Paging and tone-squelch are standard functions. Also one can be paged using DTMF tones or subaudible CTCSS tones. ICOM IC-W21AT This unit offers all of the standard features plus a couple of special functions. One is what their ad writer calls "artificial intelligence" (AI); a key can be programmed to produce the same effect that otherwise would require a number of keys to be pressed in sequence. Another is automatic output control. When talking through a repeater, the unit measures the repeater's signal strength and reduces its transmit power to the minimum required to maintain communications. The reviewers found that the feature works well with strong signals but, with weaker signals, it must be turned off. A third special feature that most reviewers liked was the "whisper" function that allows the unit to be held to one's ear and used in full duplex, like talking on a telephone. The IC-W21AT provides 35 memory channels per band, and several scanning modes. Its 2-meter receive frequency range is broader than the amateur band, but does not include the aircraft band. The list price is $623, which is second highest among the five. An average selling price among several QST advertisers is $514. Kenwood TH-78A This unit is noted as the one that has the most programmable features. The negative side of that is that it is correspondingly more difficult to program, even with the manual. After using it for two weeks, none of the reviewers felt that they had mastered the radio. The operation manual has no index and some of the instructions are not clear. A summary "Minute Manual" is also available, and helps partially to overcome the problem. Aside from the programming, the unit is reportedly easy to use. The scanning functions are notably flexible. When it is switched to a particular repeater frequency, the unit automatically selects the correct offset frequency. When programming the frequency of a particular repeater, one can add the call sign, or any other 6-character label, into the memory to remind the operator which repeater it is. The TH-78A provides a DTSS system for remote access and also paging. When it is actuated, by sending the correct DTSS code and glancing at the display, one can not only hear the audio but also see who is paging. An automatic timer will shut down the unit if it transmits continuously for more than ten minutes. In summary, the reviewers call the unit "an exceptional radio for hams who need its full-featured paging capability and other programmable functions". The list price is $599. Typical average selling price is $449. Standard C558A The reviewers commented about this unit's extremely solid "feel", but most commented that the LCD display is small and difficult to read. The frequency digits are large enough, but certain other display items, such as the offset indicator, are almost microscopic. Even the edge lighting does not help very much in dim light. This unit, like others reviewed, also received criticism for the difficulty in programming, but operation was found to be easy after the radio was programmed. The C558A comes with 20 frequency memories per band, but it can be expanded to 100 per band! The frequency scanning, also, is quite versatile and includes simultaneous 2-meter/70-cm. scan of the full bandwidth. This unit's crossband repeater function was rated the best performer among all five. Some receiver desensitization was noted during repeater operation. DTMF tones can be used for paging this unit, and also the squelch can be set to remain closed until it hears a particular subaudible tone, without requiring a page. A unique feature is a 15-dB. receive attenuator that can be used in an environment (such as a hamfest!) where a lot of H-Ts are in use. In summary, the reviewers recommend the Standard C558A as a good performer in all respects except for the LED display. Its list price is the highest of the five, at $689. The average selling price is also the highest: $529. Yaesu FT-530 This Yaesu unit is unique among the five in that it drew praise, not criticism, for its ease of programming. Several reviewers even said that they were able to program basic functions without use of the manual! But the manual is rated as excellent, written in conversational English. In addition, the ergonomic design is excellent and the display is fully readable in "all" lighting conditions. It provides 41 memory channels per band. DTMF paging and coded squelch is used. It can even be programmed to acknowledge automatically. Another programmable function is a clock/alarm system that switches on at a preset time. A battery saver function is provided that reduces power output in response to the received signal strength from a repeater. Also, the status of the battery charge can be checked from the LED display if one pushes the proper buttons. Several items are included that would be useful for mobile operation of the H-T from an automobile. Among them is an optional remote mike/speaker that contains an LED display of both frequency and signal strength. Also, a VOX circuit is provided in the radio. The 2-meter receive frequency range is 130- to 170-MHz., which provides a portion of the aircraft band. To listen to aircraft requires a manual actuation of the AM button. In summary, the Yaesu FT-530 got excellent reviews for easy operating and convenient features. The only reservations expressed were that some reviewers felt that the audio output from the speaker is a bit weak for noisy environments. The list price is $569 and the average selling price is $439. The editor's summary notes that all the rigs reviewed were found to be quality products. Performance of the radios on alkaline batteries was superior in every transceiver tested. With the advent of rechargeable alkalines, the optional battery cases deserve consideration. A negative factor common to all five manufacturers was a lack of any caution in the manual regarding crossband repeaters and links. It is absolutely necessary, before establishing a crossband repeater, that great care be taken to see that the repeater frequency selected is not in use for some other service. Simply listening and finding it temporarily unused is no indication that it is, in fact, a free frequency. One should consult the ARRL Repeater Directory and check carefully before attempting repeater operation! Also look at the band plans in the front of the book and make sure that the frequency planned is designated for FM operation. Finally, a check should be made with the local or regional coordinators. _________ Title>PR2:Trimble Scout GPS Hand-Held Global Positioning Receiver Author>Wilson, Mark - AA2Z Source>QST Mar 94, p. 77, 81. Abstract>Description of the U.S. Global Positioning System (GPS) and the Trimble Scout receiver for automatically determining exact position anywhere on earth via the GPS. Digest>The Global Positioning System (GPS) was established by the Department of Defense to allow American military personnel to determine their exact location anywhere on the face of the earth at any time. It operates from a number of satellites in orbit, several of which are always within reach of every point on the planet. Recently, the technology has been released for commercial use and the Trimble Scout is one of the latest products made available to consumers. It is a hand-held device, slightly larger than a scientific calculator, with an LCD display and eight push-buttons on its face. On command, it will display one's precise location in a number of ways: degrees, minutes, and seconds of latitude and longitude; degrees, minutes and hundredths of minutes of latitude and longitude; 6-character Maidenhead grid locators; and a number of other systems designed to be used certain kinds of maps. One can save a location to memory in one coordinate system and later view it in any of the others. When power is first turned on, the Scout scans for satellite signals and locks on as many as it can find in two minutes. Almost always, it will have little difficulty finding as many as six. Three are required to calculate position in two dimensions. With four, the unit also displays altitude above sea level. After the satellites are accessed, commands are selected from menus shown on the LCD display. Six menus are available: Location, Navigation, Library, Setup, Route, and Advanced. In the Route mode, one can enter the location of a particular destination and the Scout will calculate its distance and bearing. Also, one can specify any number of intermediate way points and the unit will show the progress being made toward each as the trip progresses. The Scout will perform many other functions, including some not connected directly with navigation. For example, it will calculate the azimuth and elevation of the moon and other celestial objects at any time. The manufacturer's list price of the Scout is $795. Accessories available include an external antenna, d.c. power cord, and other items for a list price of $225. ------------------------------------------------------------------------ HINTS AND KINKS Conductor: David Newkirk - WJ1Z Sr. Asst. Technical Editor _________ Title>HK1:Cleaning Up the Beep Tone In the Ten-Tec OMNI V Transceiver Author>Perras, Henry J. - K1ZDI Source>QST Mar 94, p. 78 Abstract>A circuit that creates a clean "whistle" tone. Digest>The keypad beep in the OMNI V is a two-KHz. raspy tone that is not "clean". Mr. Perras has designed and built a 2-KHz. bandpass filter using a dual op-amp that generates a clean "whistle". Schematics are included showing the circuit of the filter, and also where the connection points are located on the OMNI V logic board for the filter leads to be soldered in place. _________ Title>HK2:Simple Audio Attenuator Solves TNC Overload Problems Author>Booth, Lionel S. - N5LB Source>QST Mar 94, p. 79 Abstract>A modified connector containing a 20-dB. attenuator is used between the receiver and TNC to eliminate problem of excessive audio signal level input in a packet setup. Digest>When input signals from the author's Drake R-4 receiver are adjusted to the low level required by the Kamtronics KAM TNC, the volume is too low for listening. His solution was a 600-ohm pi-section attenuator inserted between the receiver and the KAM input. It uses three resistors: 3,000-ohms in series with the hot wire of the audio coax; and two of 750-ohms each, connected between the hot wire and the shield, one ahead of, and the other after, the series resistor. It provides 20-dB. attenuation. He built the attenuator inside a piece of copper tubing with a phono plug on one end and a female phono jack on the other. _________ Title>HK3:Stopping Bug and Paddle Skids Author>Moretti, Michael - WB2SRL Source>QST Mar 94, p. 79 Abstract>Suction cups from the hardware store, attached underneath a bug or paddle, stop skidding. _________ Title>HK4:Is That Hardware Stainless? Author>Mandeville, Bob - N1EDM Source>QST Mar 94, p. 79 Abstract>Determine whether hardware is stainless steel by using a magnet. Digest>The author suggests that one can easily check the hardware in the junkbox to determine whether or not it is stainless steel by using a magnet. He states that stainless steel is not magnetic, whereas most hardware is made of carbon steel that is strongly attracted to magnets. ------------------------------------------------------------------------ TECHNICAL CORRESPONDENCE (TC) Conductor: Paul Pagel - N1FB Assoc. Technical Editor _________ Title>TC1:Maximum Bandwidth Monopole Antennas Author>Formato, Richard A. - K1POO Source>QST Mar 94, pp. 80-81 Abstract>A discussion of bandwidth of vertical monopoles of varying diameter. Relatively broad bandwidths can be achieved with large diameter conductors. Large diameter conductors can be simulated by multi-wire "cage" antennas. Digest>In this letter, Mr. Formato discusses the operating bandwidth of quarter-wave monopole antennas operating against ground planes. He shows that the useful bandwidth is a function of the diameter of the antenna conductor, itself. He defines the operating bandwidth as the frequency band between SWRs of 2.5:1. This width is much broader for "fat" antenna conductors, that is with diameters an appreciable fraction of the wavelength, than with thin wire. He further defines the diameter of the antenna as D, the length of a quarter-wave in free space as L, and F(0) the frequency at which the antenna is a physical quarter wavelength. Note that, using these definitions, F(0) is not the resonant point of the antenna; resonance occurs at a few percent lower than F(0). He shows that with an antenna fed with 50-ohm cable, (1) maximum bandwidth occurs when the ratio of monopole length to diameter (L/D) is 5:1. (2) That bandwidth is approximately 50 percent of F(0). (3) The frequency of minimum SWR is about 1.3 percent less than F(0). (4) Approximately two-thirds of the bandwidth is above F(0) and one-third below it. (5) The SWR minimum is a near perfect 1.009:1. Such an antenna with dimensions of 4.35 meters (14.27-feet) long and 87 centimeters (2.85-feet) in diameter would cover 13.92 MHz. to 22.57 MHz., including the entire 20-, 17- and 15-meter bands! For such an antenna to perform precisely as calculated, the ground plane would have to be infinite. But, with 16 or more radials a half-wavelength or more long at the lowest frequency, the results would be comparable. For those to whom a 2.5 SWR is uncomfortably high, the graphs shown with the letter indicate that the bandwidth between 1.5 SWR points is about plus and minus 10 percent around F(0). Hence, at 20-meters, the bandwidth would be 2.8 MHz.! It is not necessary that the antenna conductor, itself, be solid. A "cage" of wires spaced the appropriate distance apart will behave nearly as well as solid metal. At least 8 wires should be used, preferably more. _________ Title>TC2:Toroidal-Core Color Codes Author>Czuhajewski, Michael A. - WA8MCQ Source>QST Mar 94, p. 81 Abstract>Description of several different color codes used by various manufacturers of toroidal cores. Digest>The author points out the disconcerting fact that there is no industry-wide color code for powdered-iron and ferrite core materials. Some manufacturers, such as Micrometals, Arnold Engineering, and others, have color codes of their own, some of which duplicate those of other manufacturers is some, but not all, materials. If one finds a core that is red, it MAY be powdered-iron with a permeability of 10, but it also MIGHT be a ferrite core of permeability 850, 1800, or 10,000! Be suspicious of any colored core if the manufacturer is not positively known. ------------------------------------------------------------------------ LAB NOTES (LN) Conductor: Steve Ford - WB8IMY Asst. Technical Editor _________ Title>LN1:TVI, CATVI, and VCRI Author>Hare, Ed - KA1CV Source>QST Mar 94, pp. 82-83 Abstract>Advice on how to eliminate interference from amateur radio transmissions on TV, cable TV, and VCRs. Digest>This is in the form of a fictitious conversation between Ed Hare, ARRL Lab Supervisor, and Joe Hamm, a ham who is having trouble with RFI. Mr. Hare explains the use of a low-pass filter on the output of an amateur transmitter. Next, he explains TV overload from a transmitter's fundamental signal and recommends installation of a high-pass filter at the TV set. Then, the use of a common-mode choke on the antenna lead to the TV set. Finally, he discusses the problem of the amateur's 2-meter signal leaking into a cable-TV cable and interfering with Channel 18, which is at 144.0- or 145.25-MHz., depending on the cable company. The cable company is responsible for eliminating leakage into their cable. FCC regulations require that the carrier-to-noise ratio must be at least 40-dB. and the carrier-to-coherent disturbances ratio 47-dB. at the customer's location. But any pickup in the customer's TV set, itself, is nobody's responsibility except the customer's! If the ham is confident that the transmitter is "clean", and the cable company's cable is within specifications, then it is between the neighbor and the manufacturer of his TV set. For good neighborly relations, the ham should do whatever s/he can to help the neighbor overcome the problem. ------------------------------------------------------------------------ NEW HAM COMPANION (NHC) The New Ham Companion is a regular monthly section in QST that concentrates on articles of primary interest to newcomers to ham radio. _________ Title>NHC1:Worked All Palm Beach Author>Penn, Morton - WA2STA Source>QST Mar 94, p. 60 Abstract>A contest sponsored by a local radio club encourages more ham activity by newcomers. Digest>The West Palm Beach, Florida, Amateur Radio Club faced the challenge that many clubs see; that is that many new technician and novice licensees were becoming members but not getting on the air as much as they could. In order to encourage more active participation by newcomers, the club decided to conduct activities that will draw them in. They created a contest, limited to novice, technician, and technician-plus amateurs, whether or not they were club members. The Worked All Palm Beach contest was the result. The object was to work as many stations as possible in Palm Beach County. Only five frequencies were authorized for contest contacts: 28.150 (CW), 28.400 (SSB), 144.105 (CW), 144.205 (SSB), and 146.55(FM) MHz. All contacts had to be Simplex, no repeaters allowed. Each station had to exchange signal report, its municipality, and a contact number. Requiring all contacts to be on single frequencies, thereby insuring pileups and QRM, was done deliberately. The intent was to give the newcomers experience in operating under congested conditions. The net result was highly successful and caused increased participation by numbers of newcomers. _________ Title>NHC2:Getting Started on the Magic Band Author>Neubeck, Ken - WB2AMU Source>QST Mar 94, pp. 61-63 Abstract>How to get started on the 6-Meter band. Digest>The 6-meter band, (50-54 MHz.), is called the "Magic Band" by many hams who use it, but others call it the "Forgotten Band" because of its lack of usage. One of the most exciting aspects of 6-meter operations is the frequent availability of Sporadic-E propagation. It is intermittent, almost unpredictable, most exciting when it occurs, and is independent of the sunspot cycle. Sporadic-E is caused by ion clouds that form in the E-layer of the ionosphere. They occur most commonly in the summer months, but occasional openings occur during all seasons. When the clouds are present, they act as super-efficient reflectors of radio signals and long-distance QSOs are possible with very low power and modest antennas. In addition to distance communications, 6-meters is also an excellent local band. With 50-watts and a modest antenna, the author suggests that contacts over a 100-mile radius are very reliable. _________ Title>NHC3:The Doctor is IN Author>Various Source>QST Mar 94, p. 64 Abstract>Questions and answers of interest to newcomers. Digest>This month's column answers questions about: interference caused by transmitter harmonics, and what to do about them; the balun in an antenna tuner that heats up during transmissions; a glossary of ham jargon; and incidental transmission of music from an autopatch when the caller is put on "hold". _________ Title>NHC4:PACSATs From an Apartment! Author>Schliemann, Dieter K. - KX4Y/ZS6BBH Source>QST Mar 94, pp. 65-66, 69 Abstract>Operating via satellites from a temporary location using indoor Yagi antennas. Digest>The author is a satellite enthusiast and operated two yagi-antennas on a common boom, for 2-meters and 70-cms., to work PACSATs. Recently, at a temporary location, he set them up in an unused bedroom. He was very gratified to find that the setup worked fine and he was successful in working Oscars 22, 23, and 25 with his indoor setup. _________ Title>NHC5:Plug Into PacTOR Author>Gold, Jeff - AC4HF Source>QST Mar 94, pp. 67-69 Abstract>The advantages of PacTOR mode. Digest>In this article, Mr. Gold explains what PacTOR is, what equipment is necessary to operate in the PacTOR mode, what its advantages are, and the fun he has had with it. _________ Title>NHC6:An Over-the-Dash H-T Mount Author>Leyson, Herbert - AA7XP Source>QST Mar 94, p. 70 Abstract>A simple mounting bracket for using an H-T as a mobile rig. Digest>This article describes a very simple mounting bracket into which the author hangs his H-T so that it can be used as a mobile rig while driving. It is bent out of coat-hanger wire, and after being formed to shape, it is covered with plastic tubing slipped over the wire. It is a square-ended "U-shape" with hooks at the top end that hook into the air vents that direct defroster air onto the windshield. From the vents, the wires extend across the shelf above the dashboard, and bend down over the dashboard for 2- or 3-inches (50- or 75-mm.) to the square end of the "U". The belt clip on the H-T hooks over the bottom of the "U", and the unit hangs vertically in front of the dashboard. The author states that the transceiver is secure in its mount as its own weight holds it in place, but he can instantly remove it when he leaves the car. ------------------------------------------------------------------------ RADIO TIPS (RT) These are short items, scattered among the articles in the NEW HAM COMPANION section. _________ Title>RT1:Activity Nights Author>Owen, Mike - W9IP Source>QST Mar 94, p. 63 Abstract>Regularly scheduled "activity nights" to encourage CW and SSB activity on VHF/UHF. Digest>Often, on the VHF/UHF bands, it is not easy to have a QSO. In order to encourage more CW and SSB activity on those bands, so-called Activity Nights have been agreed on in various parts of the country. The author lists a table of frequency, day, and time of Activity Nights that have been established somewhere, but does not state where that is. They should be taken as representative, not necessarily everywhere. Each operator should check with others in the area to determine what, if any, times have been set aside in that manner. The examples he lists are: Band Day and Time 50-MHz. Sunday, 6:00 pm 144 Monday, 7:00 pm 222 Tuesday, 8:00 pm 420 Thursday, 9:00 pm 902 Friday, 9:00 pm 1296 Thursday, 10:00 pm The author also cautions that most operators will make initial contacts on the established calling frequencies, then QSY to other frequencies for ragchewing. Calling frequencies are: Band Frequency 50-MHz. 50.125 SSB 144 144.100, 144.110 CW 144.200 SSB 222 222.1 SSB/CW 432 432.1 SSB/CW 902 903.1 SSB 1296 1296.1 SSB/CW _________ Title>RT2:Operating on the Road Author>Ford, Steve - WB8IMY Source>QST Mar 94, p. 70 Abstract>Safety rules for mobile operating. Digest>Operating on the road is great fun. To be sure that it is also safe, abide by the following rules: Do not operate your radio when traffic is heavy. When making an autopatch call, find a place to stop. Don't dial while driving. When talking on a repeater, pause to listen at the beginning of each transmission to listen for breakers. Use Simplex frequencies for ragchewing; leave the repeater for other uses. Do not use headphones! When you leave your car, take the radio with you. Use an outside antenna. "Rubber ducks" inside the car are poor substitutes. ------------------------------------------------------------------------ GENERAL INTEREST ARTICLES (GI) _________ Title>GI1:Amateur Radio Direction Finding in China Author>Baldwin, Richard - W1RU Source>QST Mar 94, pp. 22-24 Abstract>Description of an international RDF competition held in China. Digest>The author recounts his experiences visiting an international radio direction-finding competition that was held in China, near a section of the Great Wall. The contest was limited to two hours and ten minutes, and all movement was on foot. Competing required both radio acumen and also physical stamina! Teams came from all over the East Asia/Pacific Rim area, and one team came all the way from Bulgaria. The competition was apparently a great success, and a good time was had by all participants. _________ Title>GI2:Radio Gear of Yesteryear Author>Shrader, Bob - W6BNB SourceQST Mar 94, pp. 41-43, 57 Abstract>Basic description of spark and arc transmitters. Digest>In this article, the author describes the kinds of equipment and radio signals that were transmitted and received in the days before continuous-wave (CW) signals and vacuum tubes. Every ham has heard of spark transmitters, but the author points out that there were three types of transmitters used before vacuum tubes. One was spark, one was arc, and the third was high-frequency alternators. Spark transmitters generated highly damped waves created when a very high voltage was applied across a narrow air gap and a spark leaped across it. The spark caused a pulse of current that flowed through the primary of a "oscillation transformer" that, connected to the antenna, formed a resonant circuit. The pulse excited that circuit to form an oscillatory current that was highly damped by the loss of power due to radiation from the antenna. An arc transmitter differed from a spark transmitter in that the arc excited the oscillatory antenna circuit continuously rather than intermittently. Hence it caused a continuous wave, but not one with the spectral purity that later was generated by vacuum tubes and given the name "continuous wave", or CW. The third type of non-electronic transmitters was the high-frequency alternator transmitter. Everyone is aware that electric power is generated by 60-Hertz alternators. By building machinery with multiple poles and turning them at very high rotational speeds, it is possible to generate pure sine waves mechanically at frequencies up to nearly 100 KHz.! Some of the most powerful transmitters ever built generated pure RF signals in this manner. _________ Title>GI3:A New Outlook on Ham Radio Author>Kirkendoll, John - N0KJT Source>QST Mar 94, pp. 44-48 Abstract>How a blind ham became interested in radio and overcame the problems he faced. Digest>The author of this article is blind, and this is the story of how he became interested in ham radio. He received a great deal of help from his "Elmers", experienced hams. Now that he has overcome every hurdle on the way to the top in ham radio, and holds an Extra-class license, he is devoting much of his time to acting as an "Elmer" for others. _________ Title>GI4:Being an "Elmer" Author>Young, Phillip - WD0CFJ Source>QST Mar 94, pp. 44-47 Abstract>Personal satisfaction from helping newcomers get started in radio. Digest>Because of the close connection between this article and the preceding one, it is formatted as if it were a series of side-bars with the Kirkendoll article, above. The author, Mr. Young, acted as the "Elmer" for John Kirkendoll as well as others. He has received great personal satisfaction from his experiences. _________ Title>GI5:Anatomy of a 10-GHz. Record Author>Swedblom, Chuck - WA6EXV and Lee, Phil - W6HCC Source>QST Mar 94, pp. 48-49 Abstract>How a QSO of more than 500-miles was made on 10-GHz. Digest>On July 18, 1993, two-way exchanges were made on 10-GHz. between Mt. Ashland in southern Oregon, and Mt. Pinos in southern California, not far from Santa Barbara. The distance was 537.3 miles (865-Kms.). Contributing to the final success was the presence of other hams on other peaks strung out in a line of mountain-tops between the two end points. _________ Title>GI6:Cellular Radio and the Modern Amateur Author>Stone, Norman - WG1C Source>QST Mar 94, pp. 50-55 Abstract>Basic description of cellular radio as it is, and of probable future developments. Digest>This article begins with a comprehensive review of cellular radio as it now exists in the United States and other developed countries. In any city of any size in the USA, today, a person can drive anywhere with a phone in the car and talk continuously to another telephone located anywhere. The author makes clear that the present cellular system is only a beginning. He states cogently: "The developed countries are rapidly moving toward a Dick Tracy wrist-radio for everyone. It will communicate via satellite, or other means, anywhere in the world." _________ GI7:Title>Wally and Mike: Changing Times Author>Kearman, Jim - KR1S Source>QST Mar 94, pp. 56-57 Abstract>History of changes in ham radio over the last 40 years. Digest>This is a fictional conversation between an experienced ham and a newcomer. The old timer is explaining the state of ham radio 40 years ago, and the impact that each new development had on the hobby. ------------------------------------------------------------------------ wvanho@infinet.com