Menu English Ukrainian russian Home

Free technical library for hobbyists and professionals Free technical library


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

Alteration of the Len-M radio station at 29 MHz - FM. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Civil radio communications

Comments on the article Comments on the article

I have been working with phase modulation in the 29 MHz range since June 1991. The impetus was the article by A. Koval (UA3AFO) in RL N 2/1991 "And no accidents."

For work I use the factory transceiver "LEN". Of the existing modifications of "LEN" (B, C, M), "LEN-M" was rebuilt, which had an operating frequency of about 34 MHz.

The radio station, rebuilt by me, showed the simplicity of alteration, high reliability and convenience for more than a year of operation. Correspondents (in frequency, foreign) invariably rate the modulation quality as very good.

If there is a choice, it is necessary to take a device with an operating frequency as close as possible to 29 MHz - this will facilitate the restructuring.

The receiver of the radio station "LEN-M" is a superheterodyne with two conversions (IF frequencies - 10,7 MHz and 100 kHz). The block diagram of the receiver is shown in Fig.1.

Alteration of the Len-M radio station at 29 MHz - FM
Ris.1

The transmitter of the radio station is made according to the scheme of quadruple frequency multiplication (Fig. 2).

Alteration of the Len-M radio station at 29 MHz - FM
Ris.2

Location of boards on transceiver frames:

Fixed frame-transmitter (view from the side of the radio elements):

Quartz. Modulator LPF Amplifier
generator + и capacity
+ doublers ant. (KT920A,
staby + commut. KT920)
lysator mic. mustache
+
Keys

Movable receiver frame (view from PCB side):

auto- ULF+ Driver + Quartz 0
teak UPC1 + 2-circuit generator
UPC2+ filter
quartz. sq. gene.
filter +
UHF+ 0
mixes.

In the receiver, the local oscillator, UHF must be tuned; in the transmitter - master oscillator, modulator, frequency doublers, power amplifier, output low-pass filter.

RECEIVER

1. Local oscillator

The simplest option that requires minimal costs: you need to unsolder the quartz, the antiparasitic resistor, and replace the capacitor connected between the quartz and the base of the transistor with a jumper. Instead of soldered parts, it is necessary to install the elements shown in Fig. 3.

Alteration of the Len-M radio station at 29 MHz - FM
Ris.3

Coil L1 is wound on a correction coil frame (connected in series with quartz) and has 15 turns of PEL 0,3 wire wound turn to turn. Despite the fact that the coil is wound on a plastic frame, the frequency stability turned out to be sufficient for FM operation. A better coil can be made from a resistor VS-0,5, VS-1, VS-2 by removing the resistive layer from it and winding 12 - 15 turns of PEL 0,3 wire. It is desirable to fill the coil with BF glue and place it in the screen. Varicap - type KV102G or having a similar capacity (KV102, D901, KB 109). Capacitor C2 has a capacitance of 5-15 pF and is selected during tuning. It is advisable to use a trimmer with an air dielectric as C4, because. ceramic trimmers KPK-MP strongly "float".

In the factory version, the receiver's crystal oscillator operates according to the scheme: Fkg = Fsignal + Fpch, i.e. the local oscillator frequency is greater than the signal frequency, so it is necessary to rewind the coils of the loop at the output of the GPA and the coils of the bypass filter at the output of the GPA. The coils are wound turn to turn on the existing frames with PEL wire 0,31 15 turns (circuit capacitance 51 pF) and are tuned to resonance at a frequency of 18,85 MHz at the maximum RF voltage. At the output of the GPA should have a tuning range of 18 - 19,7 MHz.

Unsuccessfully, from the point of view of frequency stability, the GPA board is placed in the radio station case: it is located above the transmitter PA board, as a result, the heat from the terminal transistor, when operating at full power, quickly reaches the frequency setting circuit through the case, and the frequency "floats".

You can deal with this in the following way:

a) careful selection of the TKE-contour (total TKE should be equal to 0);

b) rearrange the GPA board on the transceiver frame away from the PA;

c) radical method: use an external GPA and apply RF voltage via a coaxial cable.

2. UHF

To tune UHF, you must have a generator at a frequency of about 29,6 MHz with output control and an attenuator. It is necessary to set the signal level so that it can be heard in the noise, and adjust the circuit to resonance, each time reducing the signal level at the output of the RF generator. You can use the GIR in the "soft" generation mode for tuning by turning on a small piece of wire at the output of the GIR. After that, try to catch the signal with the receiver, if this fails, increase the signal amplitude. Further - the same as in the case of the generator. To adjust the circuits, it is necessary to solder the tuning capacitor KPK-MP 8 - 30 pF from the side of the printed wiring in parallel with the circuit capacitor, to "catch" the resonance. Having determined the capacitance of the tuning capacitor by eye, we solder a constant instead of it and finally adjust the circuit with the core of the coil (be careful, the cores are fragile and filled with mastic, one careless movement can destroy them!).

If there is no RF generator, you can adjust the UHF according to the level of operation of the PN system as follows: set the sensitivity of the IF with the "per PN" knob to the response limit, but so that the noise is not heard, then adjust the circuit with a trimmer capacitor until noise appears at the output, reduce the PN level again etc., until resonance is found. You can also tune the receiver to an over-the-air signal, if available.

TRANSMITTER

The restructuring of the transmitter begins in the same order as the receiver: it is necessary to solder the quartz that shunts its resistor, and the capacitor connected in series with the quartz. Instead of a capacitor, a jumper is installed, and instead of quartz, a circuit shown in Fig. 4 is installed.

Alteration of the Len-M radio station at 29 MHz - FM
Ris.4

Then, the frequency of 7,4 MHz is set by the capacitors of the frequency-setting circuit and the circuit at the GPA output is tuned to resonance. With the specified data, the operating range of the transmitter is 29,3-29,7 MHz. The FM modulator usually requires a small adjustment of the coil core for the best signal quality (requires a monitoring receiver).

The doublers are tuned as follows: a frequency meter and an RF voltmeter are connected to the output of the doubler through a small capacitance and, selecting the capacitances of the circuits, tune the circuit at the output of the first doubler to 14,75 MHz, and at the output of the second to 29,55 MHz. The power amplifier in my case did not require adjustment (due to broadband), however, with a large difference in the operating frequency from 29 MHz, it will be necessary to select capacitors in the PA circuits. At a dangerous voltage level at the output transistor (high SWR), the red LED of the built-in SWR meter starts flashing. You can make a slight refinement to the PA circuit: instead of a trimmer resistor that regulates the output power, install either a 2,2 k variable resistor and bring it to the front panel instead of the "Dur. Receive / Receive" button, or use this button for discrete power switching. To do this, instead of a tuning resistor, you need to install two constants (3 k and 5 k), selecting them according to the required power. The QRP mode is necessary for conducting local communications and for experimental work.

To facilitate the combination of RX and TX frequencies, you can turn on the GPA TX in the receive mode, for which you need:

1) install a diode (KD522) in the power supply circuit of the GPA TX, breaking the printed conductor between the key and the GPA;

2) apply +10 V to the GPA TX through the free contact group of the "call" button (thus it will perform two functions:

"call" in TX mode and "tuning" in RX mode);

3) install a zener diode, KS 168, in the power supply circuit of the GPA TX (after the 100 Ohm ballast resistor).

Setting console

Initially, the knobs for the RX and TX tuning potentiometers were installed inside the case instead of the "Day receive / receive" and "Call" buttons, but this turned out to be very inconvenient, because. lack of space does not allow a sufficiently accurate scale to be established. Therefore, it was decided to mount the potentiometers and the stabilizer as a separate console (Fig. 5).

Alteration of the Len-M radio station at 29 MHz - FM
Ris.5

The console is connected to the transceiver using a multicore cable (4 cores), optionally shielded. There are "beaks" on the axis of the potentiometers, and graduations at 50 kHz are applied to the panel of the remote control. As experience has shown, such discreteness is sufficient for work. To control the frequency and work through repeaters, I use a frequency meter (TsSh-01) with a divider by 10 on K500IE 137 (TsSh-02).

A few words about the tactics of work on 29 FM.

The bulk of the stations operate in the frequency range 29,45 - 29,6 MHz. About the frequency 29.600 - especially. This is an international general call frequency, you cannot make QSOs here, but you can only work on a general call, and as soon as you are answered, immediately switch to another frequency. For example: "PSE QSY 29.540", or "All 10 FM, here ........ listening on 29,500".

The frequencies of the section 29,600 - 29,700 MHz are used for repeater transmitters: in these sections you can hear their call signs. For example, the Hungarian repeater HA29BME (Budapest) operating at a frequency of 685 MHz, when opened, issues its call sign by tone telegraph. The American repeater in New Boston W5NTE (1) gives out a kind of three-tone message, and occasionally the machine "pronounces" the call sign "voice".

To work through the repeater, you need to set the TX frequency to 100 kHz below the RX frequency and, after giving full power, try to open the repeater by briefly pressing the PTT. The repeater transmitter should respond with "pops" and give out its "business card".

If this fails, try scanning the transmitter at ±10 kHz by quickly depressing and releasing the PTT. Some repeaters, for example, HA4BME, are connected to a single network with 145 MHz repeaters.

Some foreign NAMs use portable (/p) and car (/m) radio stations. Agree, it is interesting to contact a radio amateur who is currently driving in a car somewhere in the vicinity of London.

For everyday communications over short distances, it is desirable to use frequencies below 29,500 MHz, but try not to interfere with satellite lovers.

In order not to miss the passage, I constantly keep the receiver turned on at 29,600.

See you on 29FM!

Author: A.Snopov (UA4CGL); Publication: N. Bolshakov, rf.atnn.ru

See other articles Section Civil radio communications.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Artificial leather for touch emulation 15.04.2024

In a modern technology world where distance is becoming increasingly commonplace, maintaining connection and a sense of closeness is important. Recent developments in artificial skin by German scientists from Saarland University represent a new era in virtual interactions. German researchers from Saarland University have developed ultra-thin films that can transmit the sensation of touch over a distance. This cutting-edge technology provides new opportunities for virtual communication, especially for those who find themselves far from their loved ones. The ultra-thin films developed by the researchers, just 50 micrometers thick, can be integrated into textiles and worn like a second skin. These films act as sensors that recognize tactile signals from mom or dad, and as actuators that transmit these movements to the baby. Parents' touch to the fabric activates sensors that react to pressure and deform the ultra-thin film. This ... >>

Petgugu Global cat litter 15.04.2024

Taking care of pets can often be a challenge, especially when it comes to keeping your home clean. A new interesting solution from the Petgugu Global startup has been presented, which will make life easier for cat owners and help them keep their home perfectly clean and tidy. Startup Petgugu Global has unveiled a unique cat toilet that can automatically flush feces, keeping your home clean and fresh. This innovative device is equipped with various smart sensors that monitor your pet's toilet activity and activate to automatically clean after use. The device connects to the sewer system and ensures efficient waste removal without the need for intervention from the owner. Additionally, the toilet has a large flushable storage capacity, making it ideal for multi-cat households. The Petgugu cat litter bowl is designed for use with water-soluble litters and offers a range of additional ... >>

The attractiveness of caring men 14.04.2024

The stereotype that women prefer "bad boys" has long been widespread. However, recent research conducted by British scientists from Monash University offers a new perspective on this issue. They looked at how women responded to men's emotional responsibility and willingness to help others. The study's findings could change our understanding of what makes men attractive to women. A study conducted by scientists from Monash University leads to new findings about men's attractiveness to women. In the experiment, women were shown photographs of men with brief stories about their behavior in various situations, including their reaction to an encounter with a homeless person. Some of the men ignored the homeless man, while others helped him, such as buying him food. A study found that men who showed empathy and kindness were more attractive to women compared to men who showed empathy and kindness. ... >>

Random news from the Archive

telephone microscope 07.10.2008

Mobile phones continue to acquire new features.

Specialists in medical devices from the University of California (USA) have designed an optical attachment for a camera phone that turns the device into a microscope with a magnification of two to 50 times. A doctor armed with such a telephone can send a photograph of a patient's blood sample from any remote location to his colleagues in a large medical center and receive advice.

Prototypes of the device are already being tested by doctors in the Philippines and Colombia. In addition, the creators of the microscope phone believe that farmers will be able to send enlarged pictures of pests or plant pathogens to specialists and receive recommendations on how to deal with misfortunes.

Other interesting news:

▪ NB3N3020 - new frequency multiplier

▪ ASUS Zenbook Flip UX360 Hybrid Notebook

▪ Pedals in front make the bike more comfortable

▪ Silicon clock, not electronic

▪ Electric bus on hydrogen

News feed of science and technology, new electronics

 

Interesting materials of the Free Technical Library:

▪ section of the site Lecture notes, cheat sheets. Selection of articles

▪ article Road traffic injuries. warning rules. Basics of safe life

▪ article What is a UFO? Detailed answer

▪ article Cuts friction. home workshop

▪ article Metal detector based on the principle of an electronic frequency meter. Encyclopedia of radio electronics and electrical engineering

▪ article Rapid nickel plating. Chemical experience

Leave your comment on this article:

Name:


Email (optional):


A comment:





All languages ​​of this page

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

www.diagram.com.ua

www.diagram.com.ua
2000-2024