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HF receiver KARLSON

The receiver circuit is a superheterodyne with double frequency conversion and a quartz first local oscillator. The use of domestic 174-series microcircuits is justified in principle due to the availability of their acquisition. Covered frequency ranges: 80 , 40 , 20 , 15 And 10 meters. Type of work: public address reception SSB And CW radio stations. Sensitivity: 0.3 µV. Nutrition: 8-9V DC, when consumed in silent mode 26mA, which makes it possible to power the receiver from a battery of the (6F22) “Krona” type.

The features of the scheme are:

tunable input selector,
input signal attenuation attenuator,
simple range switching,
using a set of quartz resonators from UW3DI,
two-level, high-speed IF AGC system,
non-tunable bandpass filter 1st IF,
use of EMF as a main selection filter,
reference oscillator with frequency correction element,
LED S-meter,
IF gain adjustment,
bass gain adjustment,
stable operation of cascades,
high repeatability of the design.

The input circuit, tunable across ranges, acts as the first high-resonance selecting device. This made it possible, with an appropriate gain margin, to abandon the range-tunable three-circuit filter of the 1st IF, thereby eliminating the cumbersome, multi-section adjustment control unit. The selective input circuit of the receiver allows operation with a coaxial antenna feeder.

To reduce the noise level, the K174PS1 microcircuit is powered with a voltage of no more than 8 V. Its load by the C7 L3 circuit is asymmetrical, because the existing symmetry of the input circuit and the quartz local oscillator is sufficient. Tuning frequencies of the 1st IF: 6.0….6.5 MHz.

The attenuator works on the principle of controlling the magnetic flux in the core. If instead of R1 you install a variable resistor with a resistance of 1 kOhm, then such a smooth attenuator will provide maximum attenuation at short circuit no less than 40 dB.

The second frequency converter with a separate GPA and amplifier on 500kHz, assembled on the K174XA2 chip. With a supply voltage of 8V, a minimum noise level of the amplifier and a high slope of the AGC control characteristic are ensured. The 500 kHz IF frequency allows full implementation of the chip's gain, which is abundant in the double-conversion circuit.

The AGC system for IF is two-level. One AGC detector diode VD6 (germanium) is quite sufficient to provide high-speed gain control of the stages. This became a possible exception from the classical variants of the circuits of all detector load resistors, except for the input of the microcircuit (at pin 9). In turn, this made it possible to reduce the capacitance of capacitor C31, which determines the gain recovery time, and further improve the dynamic characteristics of the AGC in terms of response speed. A chain of series-connected diodes VD7, VD8 forms the AGC release time constant by averaging the voltage on capacitor C31 for the recovery time to always be equal 0.7s, which eliminates the effect of signal “dropout” from the operation of powerful local transmitters. Resistor R11 creates a bias voltage on the detector VD6, providing a delay in the response of the AGC to the input signal level S = 3. When the input signal level reaches S=9 and above, the second level gain control stage begins to operate. Through a chain of series-connected diodes VD2, VD3 (silicon and germanium), the total voltage threshold for starting gain control of the RF stage of the frequency converter of the K174XA2 microcircuit is provided. At the same time, comfortable reception at sound level DX and local operators– is the same. Forced, parallel, independent supply of control voltage from the RF gain regulator, through the decoupling diode VD5, changes the IF gain to the operational level and, as a result, reduces noise without blocking the S-meter indication.

The GPA is made according to the classical design. Frequency overlap 5.5….6.0 MHz carried out by a variable capacitor with an air dielectric. To ensure temperature stability, it is necessary to use capacitors of the type C13, C16, C17 CSR. Without special measures, using a contour coil on a polystyrene frame and winding with PEV wire, stability was obtained, characterized as a change in the generation frequency in 1 hour to 120 Hz.

An audio low-pass filter consisting of C36, C37, C38 and Dr1 at the ULF input creates a cutoff audio frequencies higher 3 kHz.

The low-frequency amplifier on the K174UN4 microcircuit provides high-quality amplification for the operation of headphones or a small-sized speaker with a power of up to 1 W. Elements of private correction form the speech frequency spectrum.

Details and design.

HF transformers T1, T2 are wound into three and, accordingly, two, wires of PEV 0.1 grade on ferrite rings of any brand with a diameter of 4-10 mm. The number of turns is 10. The series windings are connected “beginning to end”.

Coils L7, L10 are used ready-made from the IF-465 pocket receiver. They are wound on sectional frames, placed in ferrite cups and enclosed in metal screens. The number of turns of the loop coils has already been completed at a frequency of 465 kHz. All that remains is to wind up the communication coils L8, L11 with PEL or PELSHO wire, 15 turns each, and rebuild the circuit with the core to a frequency of 500 kHz.

Bandpass filter coils L3, L4, L5 each have 18 turns, and L6 - 4 turns, wound with PELSHO 0.1 wire and placed in small-sized carbonyl cups of the SB type.

The input selector coils are wound on frames with a diameter of 6-8 mm, with Litz wire with windings: L1 - 8 turns, L2 - 10 turns, L3 - 30 turns (in bulk) with a tap from the 10th turn at the bottom. The L13 GPA coil has 30 turns wound on a frame with a diameter of 6-8 mm, turn to turn with 0.35 PEV wire and placed in a screen.

Small-sized variable capacitor C1 from a pocket receiver with a solid dielectric. Capacitor C12 is a small-sized type with rotation bearings and a mechanical vernier of any design, preferably with a deceleration of no more than 10 kHz per turn of the tuning knob.

One of the windings of the low-pass transformer from the pocket receiver is used as a choke Dr1 of the low-pass filter. The K174UN4 chip is equipped with a small cooling radiator.

KD522 diodes can be replaced with any silicon pulse diodes, and D9 with any HF germanium diodes. Instead of VD13, any rectifier diode can be used.

The range switch is a small biscuit type. The length of the connecting wires to the quartz resonators should be as short as possible.

During installation, the attenuator switch should be located near T1.

Settings.

Circuit tuning frequencies:

L3, C7 - 6.25 MHz L4, C8 - 6.0 MHz L5, C9 - 6.5 MHz L7, C28 - 500kHz L10, C35 - 5 00kHz

The procedure for setting up the radio receiver is as follows:

connect a frequency meter or control receiver to C22 and adjust the core L13 to set the GPA overlap frequency in the range of 5.5...6.0 MHz. If necessary, to “stretch” the capacitance, install a gray KT type constant capacitor in series with the variable capacitor of the receiver settings.
connect the RF voltmeter to L11 and rotate the core of the L10 C35 circuit to achieve its maximum reading;
connect the GSS to L6 and supply an RF unmodulated signal with a frequency of 500 kHz,
varying the gain control RF, adjust the core circuit L7 C28 to the maximum glow of the S-meter LED and the sound of beating in the loudspeaker;
connect the GSS to the antenna socket of the receiver, apply an RF unmodulated signal with the tuning frequencies of the bandpass filter of the first IF according to the three tuning frequencies of its circuits. Adjust them according to the maximum illumination of the S-meter and the volume of the beat tone;
without disconnecting the GSS from the antenna, Firstly, turn on the 80 meter reception range and send a test signal with a frequency in the middle of this range. Rotating the capacitor handle SEL find resonance maximum level reception. On the dial of the input selector settings, make a mark on the plexiglass sight in the form of a reception zone for frequencies in this range. If necessary, by adjusting the core of the contour band coil, the resonance zone can be shifted to a convenient place for reading from the dial;
the remaining sections of the bands 40m, 20m, 15m, 10a and 10b are marked on the dial with the cores of the corresponding coils adjusted in the same sequence.

It is very convenient to have three threads of a semicircle with adjustment zones: on the first, closer to the axis of the capacitor, there are marks of 80 and 40 meters, on the second (medium) marks of the ranges of 20 and 15 meters, and on the third, with a large radius, the frequency zone for adjusting the selector in the 10-meter range range.

The excess gain of the 500 kHz IF path can be compensated for by shunt resistor R9 or eliminated from the circuit altogether.

When replacing low-pass filter elements C36 Dr1 C37 C38 with an active low-pass filter assembly assembled on operational amplifiers and made in the form of a small-sized board located vertically on the main board, the electrical and operational characteristics of the receiver are significantly improved, as is the improvement of real selectivity and the reduction of tiring “white noise”. (see my article: “ Active filter low frequencies for a connected radio receiver" ).

Tests receiver were carried out as follows.

1. The following were installed on the table indoors: a TS-870 transceiver, DE1103 and KARLSON. An antenna-wire 1 meter long was connected in turn to each of these devices when receiving the same amateur radio station.

The comparative signal reception level is as follows:

- TS-870 - 8 points - KARLSON- 7 points - DEGEN 1103 - at the level of internal noise.

2. On the table to the same outdoor antenna connected: TS-870 and KARLSON. Signal level of the received control station and AGC comfort KARLSON is not inferior to the factory device, and with a clear advantage in soft, analog sound.

3. We observed work on the air of a neighbor on the IC-718 transceiver and PA on the GU-74 located 500 meters from the reception site. At the same time, the AGC is “choked” on KARLSON is not noticed, and the presence of a strong local station is not felt beyond a detuning of more than 6 kHz.

4. With the antenna turned off, maximum LF and IF gain, the level of internal noise of the receiver KARLSON when working on a 0.5 W 8 Ohm speaker, it does not attract attention.

I would be grateful to see your feedback sent to: [email protected]

10/16/2008 Addition to the article “KARLSON HF receiver”

Below are the drawings printed circuit board:

general form;
type of parts;
view of conductors from the parts side;
view of conductors from the foil side.

Option of replacing the 1st IF bandpass filter with a TV IF audio filter

The Layout program file for modernization is posted on http://cqham.ru/trx85_09.htm
File with drawings of printed circuit boards KARLSON _pcb.zip

Possible replacement of microcircuits with analogues:

K174PS1 on SO42P;
K174ХА2 on TCA440, A244D;
K561LA7 to K176LA7, CD4011;
K174UN4 - there are no analogues, but any 9-volt integrated low-frequency amplifier, for example LM386N with the appropriate switching circuit, will do.

Boris Popov (UN7CI)
Petropavlovsk, Kazakhstan. When repositioning in the 40-meter frequency range, the receiver's received frequency band includes the 40-meter broadcasting band.
To implement this mode, it is necessary to make changes to the circuit, highlighted in red.
Diode HF switch KD409 when applied to it forward voltage in SSB it shunts the coupling capacitors to the common wire.
When the voltage is removed from the diode switch in the AM, the EMF windings are bypassed by series-connected capacitors, which ensures an expansion of the EMF bandwidth to approximately 5 kHz.
To eliminate the influence of the combined AM detector on the AGC levels, the AM detector is separated into a separate branch.
The level of the LF signal when receiving AM is much lower and is compensated by the preliminary ULF on the KT3102.

S-meter switching diagram

When receiving CW signals on the KARLSON, the LED S-indicator winks cutely in time.

As an option, I bring to your attention a proven circuit for connecting a dial S-meter based on a microammeter from a tape recorder.

Zener diode and resistors provide compensation for zero readings in the absence of a useful signal and correction of deviations at S = 9.

HF receiver "KARLSON 3"

The receiver is a superheterodyne with double frequency conversion.

Features of the scheme:

Number of ranges – 11;

Thunderstorm (atmospheric static) indicator;

Wideband input filters;

Ring diode high level mixer;

Frequency grid synthesizer (PLL);

Three-input digital scale indicating the frequency of the input signal with a DAC;

Band electronic (diode) switching system;

RF wideband adjustable amplifiers based on two gate field-effect transistors;

Three-band IF filter I;

High frequency IF II providing side channel selectivity;

Quartz filter (FOS) based on PAL resonators;

Integrated path of GPA, OG amplification and detection of IF II;

High-speed AGC on IF;

Pointer S-meter;

Combined bass boost.

The block diagram of the receiver is presented on sheet #1.

Circuit design of the device sheet #2 and #3.

Receiver block diagram

The signal from the antenna Fig. 1, passes the thunderstorm indicator on the neon lamp and a vacuum lightning arrester with a breakdown voltage of 120 V (from the telephone) and through a switchable attenuator (AT) -18 dB (2 points of the S scale) enters a group of switchable bandpass filters (DFT). Depending on the amateur band width and frequency, settings are applied Various types DFT. On the 10-meter range, in all three frequency 500 kilohertz sectors, one common filter of type A is used.

KD409 diodes, which have proven themselves in channel selectors for television receivers, work as diode switches. Compared to electronic keys based on conventional silicon diodes, a reverse blocking voltage is not required here. Of course, replacing KD409 with p -i -n diodes is welcome.

Next, the sub-band filtered signal is fed to a high-frequency amplifier (UHF) assembled on a two-gate field-effect transistor KP327. Its main purpose is a low-noise amplifier with controlled gain from the system automatic adjustment gain (AGC). The diode installed in the source creates a fixed bias on the 1st gate, thereby providing a stable regulating voltage. characteristic when controlling the gain by the 2nd gate. The input impedance of such a stage is adjusted to match the DFT.

Mixer (SM) ring. Connecting two diodes in series in each arm allows you to average the V.A. shoulder characteristics and abandon the balancing resistor, which introduces losses during conversion. Such a garland of diodes requires increased amplitude (power) from the generator within 3-4V eff.

To cover all ranges using the interpolation method, the use of scarce range quartz resonators is not required here. This is achieved using a phase-locked loop (PLL)-based frequency grid synthesizer.

A quartz oscillator (QO) assembled on the K561LA7 logic and its phase inverters create a grid of frequencies (harmonics) at the input of the pulse phase detector (PD) with an interval of 500 kHz of the used quartz resonator.

At the same time, a high frequency (RF) signal from a voltage controlled oscillator (VCO) is received at the PD input. As a result of comparing the period of the VCO signals and the harmonics of the crystal oscillator (CH), a DC voltage of different polarities is present at the output of the PD, depending on the sign of the VCO frequency drift. This voltage is supplied to the varicap frequency control matrix, adding or subtracting from the DC reference voltage at the resistor divider.

Thus, by connecting range capacitors in parallel with the VCO inductor with a diode switch, input into the 500-kilohertz zone of each range is provided for a fixed frequency with auto-tuning according to Table 1.

It is interesting to note that in addition to the 11 amateur bands, the use of a frequency grid synthesizer with other fixed frequencies allows you to create other reception sectors. So, for example, 27 MHz, broadcasting 31 meters, etc.

The important thing here is that in the frequency range from 8 to 23 MHz, only one VCO inductor operates. For other frequencies higher or lower, other inductors will need to be connected.

To ensure stable amplitude across ranges, an automatic level control system (ALC) is used at the synthesizer output. The principle of its operation is based on the formation of a control voltage on the 2nd gate of the KP327, with a fixed voltage by two 1V diodes on the adder and a negative polarity of its value proportional to the RF level at the output of the synthesizer.

From a separate output, through the source decoupling follower on the KP303, the RF signal is also supplied to the first input of the digital scale counter (DSH). The frequency synthesizer must be shielded, and its power must be introduced through pass capacitors.

From the output of the ring mixer (RM), the spectrum of the converted signal is fed to an adjustable, low-noise amplifier of the first (variable) intermediate frequency (IF I), which compensates for signal losses in the passive mixer RM. Installation of a diplexer circuit after the diode mixer is not necessary for reasons of low value

IF I and its wide coverage band.

The load of IFC I is a wideband transformer (WBT) and a three-band non-tunable bandpass filter with a bandwidth of 500 kHz. The amplitude-frequency response (AFC) of the operation of such a filter is shown in Fig. 2. The resonant overlap of the passbands of two (!) adjacent amplitude characteristics is summed up and compensates for amplitude dips from the frequency difference of the series resonance circuits. The participation of the third resonance, relative to the first, is always in antiphase. Thus, the second (middle) circuit with a resonant frequency of 6.25 MHz is the main symmetrical transfer link in the middle of the passband.

There are errors in the PLL phase detector circuit. Instead of a capacitance of 33 pF there should be 0.033 µF and diodes VD4 and VD7 should be turned on in reverse polarity. The correct diagram is shown below.

Next, the spectrum of the IF I signal with a band of 6.0-6.5 MHz is fed to the MC3362 integrated circuit, which converts this frequency into IF II equal to 8867 kHz Fig. 3. This frequency value is dictated by the use of widely available PAL quartz resonators in the design of the main selection filter (FSF). In this case, the tuning frequency of the smooth range generator (VFO) must correspond to

2367-2867 kHz, as the arithmetic difference between IF II and IF I. This generation value is sufficiently stable for the temperature and mechanical stability of the GPA.

In the absence of PAL resonators, it is possible to use another 7 pcs. quartz by one frequency in the frequency range of their resonance 8.5...9.5 MHz, with a corresponding change in the tuning range of the GPA.

The GPA frequency adjustment is electronic using a multi-turn resistor.

The resonance of the quartz resonator of the reference local oscillator (LO) can be corrected by LC elements on the lower slope of the frequency response of the quartz filter (CF) to form the upper receiving sideband (USB). Changing the required reception band across bands occurs automatically (synchronously) with the selected frequency values of the synthesizer grid.

In order to increase the sensitivity of the IF II path, as well as for the presence of a third adjustable amplifier, a low-noise broadband IF II stage was introduced on two gate field-effect transistors KP327, which with three adjustable stages makes it possible to obtain a gain control depth of over 80 dB. From the load PDT of IF II, the amplitude of the IF II signal is supplied to the AGC detector. A resistor connected in series provides a time delay in response to impulse noise. The discharge time constant of the RC circuit is 1s.

Due to the high input impedance field effect transistor first stage + operational amplifier, as a highly sensitive millivoltmeter with a direct current amplifier (DCA), it became possible to use a non-polar capacitor with a capacity of 1 μF, which ensures high speed activation of the AGC ring.

To balance according to DC The S-meter is included in the bridge diagonal. This allowed, regardless of the regulating quiescent current bipolar transistor, in the absence of a useful signal, set the indicator arrow to zero.

From the control outputs of the MC3362 microcircuit, the values of the GPA and exhaust frequencies are supplied to the second and third counting inputs of the digital scale (DS), respectively.

When the GPA generation frequency goes away, a regulating voltage of the digital automatic frequency control (DAFC) appears at the output of the digital frequency control circuit, which is supplied to the built-in automatic frequency control varicap (AFC) of the microcircuit, thereby compensating for the departure of its frequency. When the electronic tuning resistor is rotated, the DAC digital frequency converter does not respond to rapid changes in the measured frequency.

I would like to note the design of the installation on the front panel of the TsSh receiver with LED matrices bright emerald glow. Reading the reception frequency value from such a display is not very pleasant for the eyes. Installing colored protective glass does not allow you to get rid of the visible viewing of the housings of the matrix group. If the indicators are covered tightly with a matte filter made of white paper under transparent plexiglass, or the plexiglass itself is treated from the inside with fine-grained sandpaper, then the appearance of luminous (translucent) display numbers acquires a civilized, mesmerizing effect! When the scale is turned off, only a white rectangle will be visible on the receiver panel, but if it is painted white, the front panel itself will be stylish.

We will use an HF converter, resulting in a short-wave double-conversion superheterodyne with a variable first IF and a quartzed first local oscillator. This solution, with a relatively low IF, provides not only good selectivity for both the adjacent channel and the mirror channel throughout the entire HF range, but also high stability of the tuning frequency. Due to this, a similar structure for constructing HF receivers (and transceivers, for example the legendary UW3DI) was very popular in the pre-synthesizer era. Since the expansion of the number of HF bands of such a receiver is limited only by the availability of quartz for the first local oscillator at the required frequencies, which, as in the old days, and, unfortunately, now, in the current difficult economic conditions, represents a certain problem, a converter was developed that covers the main HF ranges using only one (maximum two) quartz resonators. I have already implemented a similar solution in two-tube superheterodyne and showed good results.

The schematic diagram of the first version of the HF converter is shown in Fig. 2. and is already familiar to many, because in fact, it is an adaptation for semiconductors, already familiar to us from the above publication of a tube converter.

This is a four-band converter that provides reception on the 80,40,20 and 10m bands. Moreover, on 80m it performs the functions of a resonant UHF, and on the rest - a converter with a quartz local oscillator. A local oscillator, stabilized by just one non-deficient 10.7 MHz quartz (a resonant frequency in the range of 10.6-10.7 MHz is acceptable without significant differences in operation), operates on 40m and 20m on the fundamental harmonic of quartz, and on the 10th range on its third harmonic (32 ,1MHz). The scale can be a simple mechanical one with a width of 500 kHz on the ranges 80 and 20 m - direct, and 40 and 10 - reverse (similar to that used in UW3DI). To ensure the frequency ranges indicated in the diagram, the tuning range of the basic single-band receiver described in the first part of the article was chosen to be 3.3-3.8 MHz.

The signal from the antenna connector XW1 is fed to an adjustable attenuator made on a dual potentiometer 0R1 and then through the coupling coil L1 goes to a dual-circuit bandpass filter (BPF) L2C3C8, L3C19 with capacitive coupling through capacitor C12. In view of the fact that an antenna of any random length can be used with the receiver, and even when adjusted by an attenuator, the resistance of the signal source at the PDF input can vary over a wide range, in order to obtain a fairly stable frequency response under such conditions, a matching resistor R1 is installed at the PDF input. The ranges are switched using the SA1 switch. In the contact position shown in the diagram, the 28 MHz band is turned on. When switching to 14 MHz, additional loop capacitors C2, C7 and C16, C18 are connected to the circuits, shifting the resonant frequencies of the circuits to the middle of the operating range and an additional coupling capacitor C11. When switching to the 7 MHz range, additional loop capacitors C1, C6 and C15, C17 are connected, shifting the resonant frequencies of the circuits to the middle of the operating range and an additional coupling capacitor C10. When switching to the 3.5 MHz range, capacitors C5, C14 and C9 are connected to the PDF circuits, respectively. To expand the band on the 80 m band, resistor R4 was introduced. This four-band PDF is designed for the use of a large, full-size antenna and is made according to a simplified design using only two coils, which turned out to be possible thanks to several features - the upper ranges, where greater sensitivity and selectivity are required, are narrow (less than 3%), the lower 80 m, where very the level of interference is high and a sensitivity of about 3-5 μV is quite sufficient - wide (9%). The applied circuit has the highest voltage gain at 28 MHz with an almost proportional frequency reduction towards 3.5 MHz, which reduces some gain redundancy in the lower ranges.

The receiver local oscillator is made according to a capacitive three-point circuit (Colpitts version) on transistor VT1 connected with the OE. In this circuit, generation of oscillations is possible only with inductive reactance of the resonator circuit, i.e. the oscillation frequency is between the frequencies of serial and parallel resonances, and this condition is valid both at the frequency of the main resonance of quartz and at its odd harmonics. When generating at a fundamental frequency of 10.7 MHz (on the 40 and 20 m ranges), the local oscillator circuit consists of a quartz resonator ZQ1 and capacitors C4, C13. On the 10th range, using switch section SA1.3, inductor L3 with an inductance of 1 μH is connected to the collector circuit VT1 instead of load resistor R3, which, together with C13, the capacitance of the collector junction VT1 and the mounting capacitance, forms a parallel resonant circuit tuned to the frequency of the third harmonic of quartz (approximately 32.1 MHz), which ensures activation of quartz at the third harmonic. Resistor R2 determines and quite rigidly sets (due to deep OOS) the operating mode of transistor VT1 for direct current. The C22R6C24 chain protects the common power circuit from penetration of the local oscillator signal into it.

The selected DFT signal is fed to the mixer - the first gate of the field-effect transistor VT2. Its second gate receives a local oscillator voltage of the order of 1...3 Veff through capacitor C20 (in the 80m range, power is not supplied to the local oscillator and transistor VT2 operates in a typical resonant UHF mode). As a resonant load, the full winding of the communication coil L1 of the base receiver is connected to the drain VT2 (see diagram in Fig. 1), on which the signal of the 1st intermediate frequency (3300 - 3800 kHz) is isolated.

Section SA1.4 of the range switch switches the frequency of the reference local oscillator (USB signal) so that the traditional amateur radio reception of the upper sideband on the 80 and 40m bands and the lower one on the 10 and 20 m bands is ensured. The +9V converter supply voltage is stabilized integrated stabilizer DA1.

If it is possible to purchase modern small-sized quartz with a fundamental frequency (first harmonic) of 24.7-24.8 MHz, then you can make a converter for 5 ranges (see Fig. 3).
Minor changes in the switching outputs of the SA1 range switch are mainly associated with the introduction of the fifth range. To connect the Makeevskaya digital scale (TSH), a buffer amplifier VT3 and a fifth section of the switch SA1.5 (not shown in the diagram in Fig. 3), which controls the DS counting mode, are provided. The circuit turned out to be simple in appearance, but... just imagine how many wires will need to be run just between the five sections of the SA1 switch and the board!

When repeating the described converters, it is necessary to follow the traditional rules for installing RF devices and ensure a minimum length (no more than 4-5 cm) of the conductors connecting the converter to sections SA1.1, SA1.2 and SA1.3 in order to minimize the reactivity they introduce into the resonant circuits ( when installed in the form of a “web-tangle”, this is mainly inductance), which can significantly complicate the adjustment of the circuits in the upper ranges. It was the failure to comply with these rules that was the reason for the failures of some colleagues in the manufacture of tube super on printed circuit boards.

In order to simplify the design and ensure its good repeatability, a universal design of a 4/5 band converter with electronic range switching was developed, the schematic diagram of which is shown in Fig. 4.

Don't be scared! 🙂 The basis of the converter remains the same. Large quantity additional parts are a price for versatility of use and electronic control of range switching. For the four-band (single-quartz) version, all elements except those shown in orange are installed, and for the two-quartz version, all elements except those shown in green are installed. Switching of the PDF ranges is carried out using relays K1-K4, controlled by a single-section switch SA1 (i.e. only 5 wires grounded by HF). Switching the operating mode and generation frequency of the first local oscillator is carried out by transistor switches VT2, VT3, controlled by a resistive decoder R14, R17, R18, R19. The CB counting mode is controlled by the diode decoder VD3, VD5, VD6, VD7, VD10, and the received side is switched by the diode decoder VD4, VD8, VD9. These control algorithms are shown in the tables in Fig. 5.

It also reflects Features of connecting the Makeevskaya digital scale. In the old version of the TsSh (see. description), which is used in the author’s version, to set the required counting formula (see Fig. 5) in three-input mode, two control signals F8 and F9 are used. IN modern version TsSh Makeevskaya co. LED indicators called “Unique LED” (see. description) the continuity of control of the counting mode is preserved and the corresponding pins are called K1 and K2 (shown in brackets in the diagram in Fig. 4). But in the modern economical version of the TsSh Makeevskaya with LCD indicators called “Unique LCD” (see. description) the counting mode is controlled by only one output, switching either the mode of addition or subtraction of all arguments (i.e., the measured frequencies of three generators), but the counting formula we need can be pre-programmed and saved in non-volatile memory- in our case (see table Fig. 6) it is necessary to indicate that argument F3 is always negative. The same single-pin control of the counting mode is also supported by the Unique LED digital switch, so that if desired, it can be programmed and connected in the same way as the Unique LCD digital switch.

Converter design. All converter parts are mounted on a board made of single-sided foil fiberglass laminate measuring 75x75 mm. A drawing of it in lay format is available. In order to reduce the size, the board is designed to install mainly SMD components - resistors of standard size 1206, and capacitors 0805, imported small-sized electrolytic ones. Trimmers CVN6 from BARONS or similar small-sized ones. Relays with an operating voltage of 12 V are small-sized imported relays with 2 switching groups of a widely used standard size, produced under different names - N4078, HK19F, G5V-2, etc. As VT1, VT5 you can use almost any silicon n-p-n transistors with a current transfer coefficient of less than 100, BC847-BC850, MMBT3904, MMBT2222, etc., as VT2, VT3 you can use almost any silicon p-n-p transistors with a current transfer coefficient of less than 100, BC857-BC860, MMBT3906, etc. Diodes VD1-VD10 can be replaced with domestic KD521, KD522. The receiver coils L1-L4 are made on frames with a diameter of 7.5-8.5 mm with an SCR trimmer and a standard screen from the IF circuits of the color block of Soviet color televisions. Coils L2-L3 contain 13 turns of PEL, PEV wire with a diameter of 0.13-0.3 mm, wound turn to turn. Communication coil L1 is wound on top of the bottom of coil L2 and contains 2 turns, and communication coil L4 is wound on top of the bottom of coil L3 and contains 7 turns of the same wire. Choke L5, used in a single-quartz version, is a small-sized imported one (green striped). If necessary, all coils can be made on any other frames available to the radio amateur, of course changing the number of turns to obtain the required inductance and, accordingly, adjusting the printed circuit board drawing to the new design. Photo of the assembled board.

Settings is also quite simple and standard. After checking the correct installation and DC modes, we connect a tube voltmeter to the VT5 emitter (connector J4) to monitor the local oscillator voltage level alternating current(if you don’t have an industrial one, you can use a simple diode probe, similar to that described in) or an oscilloscope with a bandwidth of at least 30 MHz with a low-capacitance divider (high-resistance probe); in extreme cases, connect it through a small capacitance.

Switching to the 40 and 20m ranges, we check for the presence of an alternating voltage level of about 1-2 Veff. We similarly check the operation of the local oscillator on the 15 and 10m bands. This is for a two-quartz version, but if we make a single-quartz (quad-band) version, then we turn on the 10m range and by adjusting C25 we achieve the maximum generation voltage - it should be approximately the same level. Then, by connecting a frequency meter (FC) to connector J4, we check the local oscillator generation frequencies for compliance with the data in the table shown in Fig. 5.

If you have devices such as frequency response meter or GSS, or better yet NWT, it is better to configure the PDF independently from the base receiver. To do this, we temporarily close resistor R5 with a wire jumper so that the local oscillator signal does not interfere with us, connect a 220 ohm load resistor to connector J2, and connect it to the NWT input (or an output indicator, for example, an oscilloscope with a bandwidth of at least 30 MHz with a low-capacitance divider (high-impedance probe) sensitivity no worse than tens of mV). On antenna input connect the NWT output (GSS or frequency response meter). For correct measurements, we set its output level so that there is no noticeable overload of the two-gate transistor, which in this case works as a UHF. The absence of overload can be determined by the unchanged frequency response when the signal decreases, for example, by 10 dB or, in the case of using GSS, the proportionality of the change in its output level to the change in the input level, even by the same 10 dB. It is recommended to carry out such a check (to ensure that the measuring path is not overloaded) regularly., so as not to step on the typical rake for beginners.

And we move on to setting up the PDF, starting from the 80m range. By adjusting the trimmers of coils L2, L3, we achieve the required frequency response on the screen (if we configure it using the GSS, then we set the average frequency of the range to 3.65 MHz on it and achieve the maximum output signal). Then we move on to setting up the PDF on other bands, starting from 10m, but we don’t touch the coil cores anymore! And we adjust the trimmers corresponding to the ranges - on the range of 10m - these are C5, C20, 15m - C10, C19, 20m - C9, C18, and 40m - C8, C17.

The interconnection diagram is shown in Fig. 6. The +5V power supply is provided by an external integrated stabilizer 0DA1, mounted on the metal body of the receiver for better cooling. Filter 0С2.0R3 provides decoupling of the digital switch supply and reduces the heating of the 0DA1 stabilizer when using digital switch with LED indicators, consuming up to 200 mA. When connecting the economical “Unique LCD” digital switch, which consumes only 18 mA, the recommended filter ratings are indicated in parentheses, and the permissible power dissipation of resistor 0R3 can be reduced to 0.125 W. After connecting the converter (if the boards were configured separately from each other) to the base receiver, you need to check whether the pairing of the first circuit of the 1st IF (on coil L2 Fig. 1.) has gone missing and, if necessary, adjust it according to the method outlined in the first part of the article. It is better to do this on some wide range, for example on 10 or 15m, so that the PDF does not significantly limit the bandwidth of the entire RF/IF path of the receiver when tuning across the entire range of the 1st IF.

Photo appearance assembled five-band receiver

photo of its installation:

A correctly configured receiver has a sensitivity at s/n = 10 dB no worse (probably noticeably better, but I can’t measure it more accurately with the equipment now available) 0.4 µV (10m) to 2 µV (80m). For a long time the receiver was tested with a surrogate antenna (15 meters of wire from the 4th floor to a tree), I like how it works. Thanks to the wonderful GDR-rovsky EMF, it sounds juicy and beautiful (as long as the frequency neighbors don’t interfere 🙂), efficient (I almost never use an attenuator) and the AGC works smoothly, the GPA frequency is quite stable without any thermal stabilization work, the initial run-out is less than 1 kHz, therefore, immediately upon switching on, the Makeevskaya DAC is activated and you can use the receiver without any warm-up - the frequency stands rooted to the spot during any switching of bands.

You can discuss the design of the receiver, express your opinion and suggestions at forum

S. Belenetsky,US5MSQ Kiev, Ukraine

Main technical characteristics:

Frequency range………………………………………………………………...... 80 - 10 m,

Modulation type…………………………………………………………………………… SSB,

Sensitivity……………………………………………………………...0.3 µV,

Bandwidth……………………………………………………………… 2.4 kHz,

Dynamic range………………………………………………………........ 100 dB,

Suppression of inter.mod. not less…………………………….. – 70 dB,

Switchable UHF……………………………………………...+8 dB,

Disable impulse suppressor interferenceduration ... from 0.1 μs to 2 ms,

Tunable notch filter with band………...70 Hz,

Depth of suppression not less than……………………………... – 65 dB,

Two-level IF AGC with dynamic limiting... 85 dB,

Supply voltage………………………………………………………......... 12 - 13.8 V,

Current consumption……………………………………………………………........... 65 mA.

The structure consists of three blocks:

Receiver main board;

GPA unit;

Digital scale-frequency meter.

Replacing the last two blocks with an integrated frequency synthesizer allows you to create a compact receiver design with an additional set of service functions.

Below are circuit diagrams main unit and GPA.

Digital scale – “Makeevskaya”.

To simplify and not to clutter the drawing, there is no numbering of radio elements in the diagram.

The receiver is a double frequency conversion superheterodyne with fixed IFs. This decision was made due to the problems of manufacturing high-quality quartz filters with one conversion and distributing the gain across frequencies with double conversion in order to obtain stable amplification as a whole.

The use of SIF TV as a pre-selection filter with a passband of 300 kHz protects the K174XA2 input from powerful out-of-band interference, and also simplifies the selection of quartz resonators for the 1st IF and XO with a spacing of 500 kHz. Imported analogue filter FP1P8-62.0 ( yellow dot on the body) – SFT5.5MA.

The IF value, depending on the filter used, can be 6.5 MHz with appropriate adjustment of the frequencies of the VFO and quartz resonators.

The K174XA2 chip, in addition to high gain at a frequency of 500 kHz, has built-in stages of effective AGC.

A highly dynamic, switchable AMP is in demand in the HF bands.

The use of a double balanced mixer provides a high level of intermodulation interference suppression.

Suppression of the interfering carrier is carried out by switching on a serial resonance quartz resonator in parallel with the oscillatory circuit and an EMF tunable in the passband using a variable capacitor with a solid dielectric from a pocket receiver, the sections of which are paralleled.

When several resonators are connected in series, the rejection band decreases. So, with one resonator (at a level of 6/50 dB) - 400/1000 Hz, with two - 200/450 Hz and with three - 70/200 Hz.

The p-i-n diode turns off the NOTCH node.

A short comment on the operation of the impulse noise suppressor (NB) circuit.

All modern transceivers have a built-in NB, but only a few operators use it, and mainly when there is interference from the car’s ignition, because the NB reacts clearly only to them (single ones); it reacts mediocrely to lightning discharges (smeared).

Most importantly, when receiving a powerful station near a frequency (outside the filter passband), the useful signal is distorted, because In the voice spectrum of the SSB signal there are short pulses that, in the form of keying the receiving path, “tear” the useful signal.

A time delay was introduced into the KARLSON-II receiver circuit for operation far after the end of the interference pulse based on a one-shot device assembled on the K561LA7 logic.

Thus, interference with a duration of 1 μs to 2 ms fits into the interval of a running monostable with delay elements of 2 ms.

When checking the functionality of this circuit unit, the receiver did not respond at all to the pulses of a gas electric lighter near the antenna itself and in the distance. Smeared pulses from light switches are also successfully suppressed. I think that the lightning strikes are over.

It should be noted that the S-meter reading in the receiver is not blocked by the IF (RF) gain knob. This was done specifically in order to set the desired gain and read the S-meter reading at it, and not like in imported devices.

That is, “as I hear, so I see.”

The circuit tuning frequencies in the diagram are highlighted in red.

An active low-pass filter assembled on low-noise operational amplifiers cuts off frequencies above 2.4 kHz, thereby suppressing tiring “white” noise and adjusts the frequency response of the EMF to the characteristics of comfortable broadcast reception.

Job electrical diagram The KARLSON-II receiver can be characterized in comparison with the reception performance of the IC-706MKII transceiver.

So, while listening to the same SSB memorial station on May 9, operating from the 3rd district on the 20-meter band, someone from Western Europe began to jam it (you can guess who!) and the IC received only " porridge."

The KARLSON-II radio path allowed me to continue to clearly hear the memorial and this asshole at the same time.

B. Popov (UN7CI)

Petropavlovsk, Kazakhstan

The use of SIF TV as a pre-selection filter with a passband of 300 kHz protects the K174XA2 input from powerful out-of-band interference, and also simplifies the selection of quartz resonators for the 1st IF and XO with a spacing of 500 kHz. An imported analogue of the FP1P8-62.0 filter (yellow dot on the body) is SFT5.5MA.