Conex Club Magazine - no.9 - 2001

Conex Club Magazine - No. 9 - 2001 - AD797 (Ultralow Distortion, Ultralow Noise Op Amp)

Reading time: 3 minute

The main topics presented

1. AD797 (Ultralow Distortion, Ultralow Noise Op Amp)

The AD797 circuit is a microphone amplifier very low noise with applications especially in radiocommunication systems. The capsule contains three operational amplifiers that can be interconnected in various ways but for the same purpose.

The amplification can be controlled in steps of 5dB, can reach 20..30dB. The power supply is differential with 17V.

2. AD831 (Low Distortion Mixer)

The AD831 circuit is a double-band balanced double mixer that can reach up to 500MHz.

The recommended local oscillator level is -10dBm and can be reduced to -20dBm (32mV) if the frequency is below 100 MHz. At 500 MHz the conversion is ensured for the 100mV (-10dBm) level.

The impedance for RF and LO signals is 50 Ohm. The power supply is made with double voltage +/- 5V or single 9-11V.

3. Microprocessors and microcontrollers (dynamic light)

It presents a simple application of an 8031/8051 series microcontroller - a dynamic light with eight LEDs and microprocessor.

An Atmel integrated circuit is used, with a small number of pins (only 20, in a narrow capsule) - AT89C2051. This avoids the disadvantage of 80C51 type circuits, with "large" capsule, with 40 pins.

4. Evaluation of the current capability of the printed circuit paths

Printed circuit paths, due to the low values ​​of their geometric parameters ("path width" and "conductive foil thickness"), do not allow the passage of currents no matter how high.

For this reason, designers and users of electronic PCB modules must take into account, among many other more or less important issues, the current capability of the interconnection routes.

5. Infrared remote control with 16 channels

Technical data:

  • Transmission type: infrared with RC-4 coding;
  • Minimum action distance: 6m in artificial lighting conditions or during the day 6m;
  • Number of digital channels: 16 with selectable logic and momentary actuation;
  • Maximum current absorbed or debited: 10mA / 12V on any output;
  • Receiver power supply: 12V stabilized source;
  • Transmitter power supply: 9V - 6F22 battery.

6. ECAL 2.0 - Calculation program in the field of passive circuits

ECAL is a small software system for primary calculations in the field of passive components and circuits (RLC).

It is useful for amateur electronics engineers in trying to get quick answers in the absence of pencil and paper, but it can also be used successfully by high school students or students who test their knowledge of electricity at school.

7. Watch TV Clock

Experienced TV receiver repairers know that any color device set correctly on a black and white mirror will no longer need further convergence or RGB overlay adjustments. That is why there is a wonder with a complex image and sound.

So, in addition to the image strictly necessary for adjustment, it has at the top of the screen a text that scrolls from right to left, and at the bottom an interesting digital clock.

Due to the multiple possibilities offered by the microcontroller PIC16F84 </strong> Microcontroller. we can simplify the electronic scheme to the maximum.

By implementing a set of instructions we obtain on pin 17 the two synchronization signals V and H and on pins 10, 2, 1 and 18, the video signal in gray tones.

These are added with a network of resistors and are applied to an RF modulator of the type used in videocassettes or built according to a preferred scheme.

The signal generated on pin 7 is applied to the audio input. The clock is adjusted from the two keys, SWH and SWM.

If the execution of the assembly does not pose problems even for beginners, the realization of the program requires the careful study of the set of instructions contained in the microcontroller manual.

8. MC1496 / MC1596

One of the most used telecommunications circuits produced by Motorola is the circuit MC1496 - MC1596. This circuit has been designed for balanced modulator-demodulator functions.

It is widely used by amateur builders, especially radio amateurs who build equipment for the module SSB (J3E).

9. PA - 500W

Radio traffic, especially in international competitions, requires the use of adequate equipment with outstanding technical performance, among which power plays a key role.

Of course, the equipment of the stations is a concern for many radio amateurs and this is due to the publication of this article. This amplifier was selected because it has elements that are easy to purchase even in the amateur radio network.

10. Electronic entertainment

Among the highly appreciated and practiced games is the well-known ping-pong, which, in the absence of a suitable space to set the table, can also be played on the screen of a television receiver.

This solution is given a prestigious solution by the magazine "Practical Electronics" in number 257 by presenting a ping-pong game whose main element is PIC16F84-10P.


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