Range low-pass filter switch in transistor power amplifiers. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

Range low-pass filter switch in transistor power amplifiers. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Knots of amateur radio equipment. Filters and matching devices

Comments on the article

When manufacturing a low-pass filter, to a transistor power amplifier, at the output of which there are two KT957, the question arose, how is it more expedient to switch filters? Typically, the low-pass filter is switched using relays that are energized in the operating range. To get rid of this, the author installed polarized relays RPS-32, because.

for switching, they require a short-term voltage supply to the "working" windings. In addition, using these relays to increase reliability, it is convenient to connect both groups of contacts in parallel. The voltage to the relay is supplied from the power amplifier power supply.

When the power amplifier power supply is initially turned on, through the normally closed contacts K13.1 of the K13 relay (Fig. 1), the lithium circuit of the "working" windings of the K7-1 and K8-1 relays is closed.

Range low-pass filter switch in transistor power amplifiers
Ris.1

The contacts of these relays K7.1 (2) and K8.1 (2) connect the low-pass filter of the 20-meter range to the output of the power amplifier and the matching device (Fig. 2). At the same time, through the VD16-VD20 diodes, power is supplied to the "pull-off" windings K1-2, ... K6-2, K9-2, ... K12-2 of the relay of the remaining ranges (Fig. 1), which leads to a short circuit to the low-pass filter housing other ranges as shown in Fig.2.

Range low-pass filter switch in transistor power amplifiers
Ris.2

In series with the relay winding K13, resistance R1 is connected, and in parallel with the relay winding, an electrolytic capacitor of 15,0 microfarads is connected. The capacitor is charged, the K13 relay is activated and de-energizes the "working" windings of the 13.1-meter range and the "blow-off" windings of the rest with contact K20.

When switching to another range, you must briefly press the corresponding button S1-S6. In this case, the power supply circuit of the "working" windings of the selected range will be closed, and through the diodes - the "flip" windings of the relays of the remaining ranges. The current flows through the relay only for the time the buttons S1-S6 are pressed until certain relays are activated.

At the LPF input, the relay contacts are connected in parallel (Fig. 2). At the output - one group can be used to switch the LEDs indicating the included range.

Details

As VD1...VD30, KD908A diode assemblies were used, which made it possible to reduce the dimensions of the printed circuit board. VD31....VD42 - KD510 or similar. Instead of the RPS-32 relay, you can use the RPS-20. Relay K13 - RES34, for an operating voltage of 12-18 V, other similar relays can be used. Blocking capacitors C1 ... C24 of 0,01-0,1 μF, for an operating voltage of at least 40 V.

The entire setting of the switch comes down to the selection of the resistance R1, to force the 20-meter range to turn on after the power is turned on.

The low-pass filter switch works with a transistor amplifier with an output power of about 250 watts. The low-pass filters are made according to the standard scheme and were tuned using a frequency response meter.

Author: Nikolai Kononov (RW6HW), Stavropol; Publication: N. Bolshakov, rf.atnn.ru

See other articles Section Knots of amateur radio equipment. Filters and matching devices.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

The threat of space debris to the Earth's magnetic field 01.05.2024

More and more often we hear about an increase in the amount of space debris surrounding our planet. However, it is not only active satellites and spacecraft that contribute to this problem, but also debris from old missions. The growing number of satellites launched by companies like SpaceX creates not only opportunities for the development of the Internet, but also serious threats to space security. Experts are now turning their attention to the potential implications for the Earth's magnetic field. Dr. Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics emphasizes that companies are rapidly deploying satellite constellations, and the number of satellites could grow to 100 in the next decade. The rapid development of these cosmic armadas of satellites can lead to contamination of the Earth's plasma environment with dangerous debris and a threat to the stability of the magnetosphere. Metal debris from used rockets can disrupt the ionosphere and magnetosphere. Both of these systems play a key role in protecting the atmosphere and maintaining ... >>

Solidification of bulk substances 30.04.2024

There are quite a few mysteries in the world of science, and one of them is the strange behavior of bulk materials. They may behave like a solid but suddenly turn into a flowing liquid. This phenomenon has attracted the attention of many researchers, and we may finally be getting closer to solving this mystery. Imagine sand in an hourglass. It usually flows freely, but in some cases its particles begin to get stuck, turning from a liquid to a solid. This transition has important implications for many areas, from drug production to construction. Researchers from the USA have attempted to describe this phenomenon and come closer to understanding it. In the study, the scientists conducted simulations in the laboratory using data from bags of polystyrene beads. They found that the vibrations within these sets had specific frequencies, meaning that only certain types of vibrations could travel through the material. Received ... >>

Random news from the Archive

19" LCD display from Buffalo Corporation 08.01.2004

Buffalo Corporation has released the FTD-G911 AD - 19" LCD display with the new MVA TFT matrix. The display went on sale at the end of December for about 770 USD.

Maximum screen resolution - 1280x1024 pixels Display brightness - 250 cd/m2, contrast ratio - 600:1, viewing angle - 170 degrees in any direction, response time - 25 ms. Connection interface - D-Sub and DVI-I. Dimensions - width 415 mm, thickness 193 mm, height 437 mm, weight - 7,4 kg.

Other interesting news:

▪ Water turns into fuel

▪ Revolutionary smartphone from Nokia

▪ HDR10+ High Dynamic Range Open Video Standard

▪ High power controller with over 90% efficiency

▪ Solid state optical nanodrive

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Normative documentation on labor protection. Article selection

▪ article What gets away with thieves, thieves are beaten for that. Popular expression

▪ How long can a camel go without water? Detailed answer

▪ article Technician-defectoscopist for magnetic and ultrasonic testing. Standard instruction on labor protection

▪ article Oscilloscope calibrator. Encyclopedia of radio electronics and electrical engineering

▪ article Traveling scarf. Focus Secret

Leave your comment on this article:

All languages of this page

Home page | Library | Articles | Website map | Site Reviews