Project Solutions

High-End-Preamp （6）

Published:2011/7/24 22:54:00 Author:Amy

By Benjamin Hinrichs Stable supply A large part of the stabilisation, decoupling and hum suppression for the supply voltages takes place locally on the main circuit board, for both the digital portion (+5 V) and the ana­logue portion (5V). The only other thing you need is a sufficiently stable source of symmetrical DC voltages (which shouldn’t be a problem with the low current c...   (View)

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DIY RF Inductors--The ABCs of inductors （2）

Published:2011/7/24 22:52:00 Author:Li xiao na

By B. Kainka Inductors with cores RF inductor forms with threaded ferrite cores are often used in practice. The core increases the inductance, typically by a factor of four or even more. The inductor can be tuned by adjusting how far the threaded core is screwed into the inductor. Ferrite cores are made for specific frequency ranges, within which they exhibit small energy losses. (View)

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High-End-Preamp （5）

Published:2011/7/24 22:37:00 Author:Amy

By Benjamin Hinrichs Channel switching The input channels are switched on the relay board. The circuit shown in Figure 3 allows two different wiring options. With the traditional option, all eight inputs from the Cinch sockets are used, with a single output to the main circuit board. This requires JP2 and JP3...   (View)

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Propagation - the total surprise factor

Published:2011/7/24 22:36:00 Author:Phyllis

The propagation of radio waves is a fascinating phenomenon because most of it is guessv/ork and sheer surprise. That is not to say the subject has not been studied extensively by researchers and radio amateurs — far from it, a number of underlying principles have been described in scientific terms as early as the 1920s by Nobel Laureate Sir Edward V. Appleton (1892-1965). Appleton discovered thai radio waves, depen...   (View)

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DIY RF Inductors--The ABCs of inductors （1）

Published:2011/7/24 22:29:00 Author:Li xiao na

By B. Kainka Electronics hobbyists often wish to copy a circuit for which suitable coils or fixed inductors are not readily available. However, you can wind just about any type of inductor if you only know how. Or you can take inductors from old equipment and modify or adjust them. All you have to do is determine is how many turns you need. (View)

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A dipole antenna for 4 meters （2）

Published:2011/7/24 22:23:00 Author:Phyllis

Receiver sensitivity measurement With the generator tuned to the receiver (or was it the other v/ay around?) a great moment arrives — v/e’re ready to decrease the RF output level on the generator until the receiver under investigation loses the signal. The VHF-Low Explorer not having an adjustable squelch or squelch defeat switch, the transition from ’very noisy signal’ to ’muted’ was found to be...   (View)

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A dipole antenna for 4 meters （1）

Published:2011/7/24 22:12:00 Author:Phyllis

No receiver is complete without a matching antenna. Commercial offerings for the 4-m band being few and far between (or scrapped by PMR fleet owners), we decided to present a design for a low-budget get-u-going dipole. Not sophisticated, want a directional antenna? Then try the links at the end of this article. Too difficult? It doesn’t get much simpler than this, so give this antenna design a try and you’ll be ple...   (View)

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High-End-Preamp （4）

Published:2011/7/24 21:30:00 Author:Amy

By Benjamin Hinrichs The multitude of options for construct­ing your ’personalised’ high-end pre­amplifier mean that you must read this second part of the article before you order the parts and take up your sol­dering iron. This is because your requirements determine how many cir­cuit boards of which type you will need, as well as which components you will need. You can con...   (View)

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Design Your Own IC: Prototyping with CPLDs （part 3）

Published:2011/7/22 3:15:00 Author:Amy

by Paul Goossens Software PC software that can generate the nec­essary programming files and program them into the IC is required for pro-grarriming the CPLD. Fortunately, the manufacturer of the CPLD has a nice (and free) software package for this purpose (see Figure 6). This software is called Quartus, and it can be down­loaded from the manufacturer’s web­site (http...   (View)

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High-End-Preamp （3）

Published:2011/7/22 3:08:00 Author:Phyllis

By Benjamin Hinrichs The control centre The main circuit board, which forms the control centre for the preamplifier, requires surprisingly few components. This is due to the high integration density of the two ICs used here. By far the majority of the components are used to generate clean supply voltages. The circuit is split into an analogue portion and a digital portion...   (View)

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High-End-Preamp （2）

Published:2011/7/22 2:47:00 Author:Phyllis

By Benjamin Hinrichs The PGA23I1 stereo audio volume control IC Admittedly, the idea of using a ’digital’ IC for volume adjustment, and further more controlling it using a microcontroller, may evoke a sceptical frown from many an audiophile. Ten years or more ago, this scepticism would certainly have been justified, but the semiconductor industry has made enormous...   (View)

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Design Your Own IC: Prototyping with CPLDs （part 2）

Published:2011/7/22 2:29:00 Author:Amy

by Paul Goossens Experimenter’s board Our experimenter’s board has a rea­sonably simple design. Nevertheless, it has more than enough I/O for per­forming our initial experiments with CPLDs. Naturally, all of the relevant pins of the CPLD are brought out via several connectors, to allow external hardware to work together with the board afterwards. The schematic diag...   (View)

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High-End-Preamp （1）

Published:2011/7/22 2:27:00 Author:Phyllis

By Benjamin Hinrichs The modern design of this preamplifiers yields audiophile specs, convenient operation and an attractive price. This is made possible by using a top-end digitally controlled attenuator/amplifier IC. Analogue audio electronics appears to have entered a dormant stage. In our present age of CDs, DVDs and MP3, traditional preamplifiers have been relegated to the role...   (View)

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Design Your Own IC: Prototyping with CPLDs （part 1）

Published:2011/7/22 2:14:00 Author:Amy

by Paul Goossens Designing a circuit always involves several somewhat disagreeable tasks, such as soldering, looking up the pinouts of ICs and laying out a maze of tracks on a printed circuit board. All of this is now no longer necessary, since you can program your own digital circuit in a CPLD. Experimenter’s board features -CPLD version: EPM7128 -JTAG interface -all I/O lines...   (View)

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Digital Alarm Clock-- Based on a PIC micro （4）

Published:2011/7/22 2:12:00 Author:Li xiao na

by M. Conde de Almeida Construction The artwork of the PCB designed for the clock is shown in Figure 3. The PCB has to be cut in two to separate the main board from the display board. Start by soldering the wire links onto the main board. Then follow the five IC sockets and all low-profile components. The rest of th...   (View)

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Digital Alarm Clock-- Based on a PIC micro （3）

Published:2011/7/22 1:46:00 Author:Li xiao na

by M. Conde de Almeida Control software The entire clock program was written in the PIC Assembly Language using the MPLAB Integrated Development Environment (v. 5.70.40) supplied free of charge by Microchip. The source code and Hex files containing the program ready to be flashed into the PIC microcontroller can be obtained free of charge from the Publisher’s website, see t...   (View)

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Digital Alarm Clock-- Based on a PIC micro （2）

Published:2011/7/22 1:17:00 Author:Li xiao na

by M. Conde de Almeida The hardware Figure 1 shows the complete circuit diagram of the clock. All intelligence (and a lot of logic) is vested in the PIC16F84 MCU in position IC5. Using RA0-RA4 and RB5-RB7 as input port lines and RB0-RB4 as output port lines, a fair amount of executable code run from the on-chip memory is able to take total control of the circuit, requiring just a 5-...   (View)

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Digital Alarm Clock——Based on a PIC micro （1）

Published:2011/7/22 0:55:00 Author:Li xiao na

by M. Conde de Almeida Although digital alarm clocks have been around for years, most of today’s off the shelf products suffer from serious design limitations. For example, many don’t keep track of weekdays and can only store one alarm time. High time for a home-brew design that does a better job. Off the shelf alarm clo...   (View)

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Hands-on CPLDs -Part I: Experimental rev counter （5）

Published:2011/7/21 1:14:00 Author:Li xiao na

By A. Rosenkranzer The PCB and future developments A double-sided PCB has been produced specifically for this tachometer project. The PCB and component placement diagram is shown in Figure 3. Component mounting should be fairly straightforward but take care not to allow any solder debris to enter underneath the PLCC socket where it could short between PCB tracks. Correct orientation of the IC is i...   (View)

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Hands-on CPLDs -Part I: Experimental rev counter （4）

Published:2011/7/20 22:46:00 Author:Li xiao na

By A. Rosenkranzer The remainder Power for the circuit is supplied by the 12 V vehicle battery via connector Kl. Diode Dl prevents damage to the circuit if the supply polarity gets mixed up. LI filters noise spikes on the supply to the 5 V regulator IC2 while CI and C2 are also used to provide noise decoupling. The complete circuit takes about 0.5 A worst case so power dissipation i...   (View)

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