also called for operation on the 40 Lo range. In this case, it turns into a system of half-wave vibrators. The use of such an antenna on other bands is not practical due to the possibility of using more efficient antennas.
When working in urban conditions, the described antenna showed good results. It allows semi-
In recent years, supermodulation has been widely used in amateur radio designs. However, the desire to make maximum use of the energy capabilities of screen voltage modulation often leads to signal distortion. Practical testing of modulators with different modulating valves
L,BNVP JlzriJZ3
There are three options for characteristics that provide optimal communication conditions: depending on the operating conditions, you can get either maximum amplification of the correspondent’s signal (Fig. 2, a) or maximum attenuation of the interfering station (Fig. 2, b).
E. ELINEVICH, Talli (UR2CG)
power lengthens the straight section of the modulation characteristic.
Circuits that allow two-grid modulation are shown in Fig. 1 and 2. Essentially, they differ only in the types of lamps used and in the fact that in the circuit of Fig. 1 displacement is carried out due to the grid current.
When using two-grid modulation, all correspondents noted an increase in signal strength and a clear improvement in modulation quality and intelligibility. Long-term operation of transmitters on radio stations UA3RV and UA3RQ, as well as evaluation of signal quality by Soviet
and foreign correspondents, allow us to recommend the diagrams in Fig. 1 and 2 for repetition.
The following should be noted: it is advisable to power the filament of the modulating lamp from a separate source; the selection of the values of Rs and Ci" must be approached carefully, since an excessively large connection of grids can damage the L2 lamp or lead to an expansion of the signal bandwidth.
The most acceptable type of work should be considered the following mode:
at which during pauses the anode current is approximately 20% -25% of the telegraph current.
V. Tamboe (EA3RY)
Double grid CLC modulation
RECEIVER CASE
(6N7S, 6N6P, 6S19P, 6PZS) on transmitters that used GU-50, GU-29 and GK-71 lamps in the final stage showed that even a slight excess of the screen voltage leads to the appearance of nonlinear distortions and an expansion of the signal bandwidth.
In order to obtain 100% modulation, reduce nonlinear distortions and rationally use the advantages of supermodulation, the author used screen voltage modulation and simultaneous modulation on the control grid. In this case, the voltage on the screen grid and the RF voltage on the control grid change according to the same law. This condition makes a correction to the modulation (dynamic) characteristic. In addition, such modulation allows the peak power of the telegraph mode to be exceeded without unduly boosting the screen voltage. It should be noted that some reduction in screen voltage without compromising
“Where can I buy a housing for transistors in “Radio”, 1968, No. 6 and No. 9?” - a new receiver, the description of which is asked by many readers.
As the chief designer of the Moscow EMA plant, T. Parafenyuk M. G. told us, the company has begun producing cases convenient for placing receivers of this type. Case size 152x90X36 mm. The internal projections and positioning of the mounting posts for the board and speaker are the same as in the widely used Sokol receiver. Therefore, the housing can be used as a backup to the factory receiver.
The body is made of impact-resistant bostyrene oxide in various colors. The kit, along with mounting screws and a scale, includes a description and instructions for setting up a superheterodyne amateur receiver with seven transistors.
The photo shows a general view of the body and cover of the receiver case.
RADKO No. 2 .1969 O 89
NEW SUPERMODULATION METHOD
(Based on materials from Amaterske Radio magazine)
“What hasn't been said about amplitude modulation? It seems that all possible AM options have been studied and described: anode, various grids, and supermodulation... So what else is there to write about amplitude modulation?”
With these words begins an article by Jan Szyma (OKUX), a master of radio sports, published in issue No. 8 of the magazine “Amaterske Radio” for 1960. The article is entitled: "Modulation by a serial, gated tube." Simple, economical and, at the same time, more effective compared to other screen modulation schemes, this scheme has been used since May 1960 on the UA3CH radio station. In a short time, its undeniable advantage over the scheme described by Comrade Shadsky - UA3BW (Radio No. 2, 1959) was revealed. The modulator does not have a modulation transformer, eliminating the need to amplify the low-frequency power.
A shortened translation of the article is given below. Minor changes have been made to the modulator circuit due to the use of domestically produced lamps.
The article says: - Modulation onto the screen grid can be done in different ways. Recently, screen modulation has been used to obtain the so-called “supermodulation”, which allows modulation “peaks” to exceed telegraph power, which until recently was considered possible only with anode-screen modulation. The proposed modulation method makes it possible to change its mode within a wide range from “symmetrical” to a mode with an adjustable carrier level (known as CLC - controlled level carrier), in which during pauses the carrier radiation is several times less than the carrier frequency level of conventional “traditional” AM schemes . Changes in the carrier level in time with modulation, as well as the physical process during the described modulation method, when the modulating voltage source is the power source of the screen grid and a number of other circuit features create the conditions for obtaining deep, almost 100% modulation without the danger of overmodulation. This was confirmed during the operation of the same transmitter with both anode-screen and supermodulation. The well-known method of screen modulation with a modulator lamp connected in parallel (Fig. 1, a) cannot give any gain, since at resistance R (or LF choke),
being the load of the modulating lamp L2, part of the voltage supplying its screen grid also drops. Increasing the modulation depth beyond 70% with such a circuit is almost impossible without distortion. The use of sequential switching on of a modulation lamp (Fig. 1.6) opens
completely new opportunities that were underestimated before. One of them is the possibility of fully using the dynamic characteristics of the lamp when switched on in this way and forms the basis of the principle of the described method. On the diagram (Fig. 2)
it can be seen that the sound voltage from the microphone amplifier is supplied to the grid of the lamp Lg, the operating point of which is set by potentiometer R. The value Ri determines the maximum anode current of the lamp Li when it is open. The Lg lamp works as a cathode follower. The operating point of the lamp Lg depends on the data of the divider Rs Ri- The value of Rs must be commensurate with or exceed /?-, the locked lamp Lg. The optimal value of the modulating voltage on the screen grid of the modulated lamps depends on the correct choice of resistance Rs.
py. The blocking voltage -100 V, to which the cathodes Lg and Lg are connected, can be taken from the grid bias rectifier of the transmitter. Lamp L, in the absence of U3B on its grid, is open, lamp L2 is closed, and the voltage on the screen grid of the output stage lamp (PA) is close to zero. If there is voltage on the grid of the Lg lamp, it begins to close, and the current through Lg increases, and the voltage on the screen grid of the RA lamp increases, and the faster, the greater the anode current of the Lg lamp and the lower the internal resistance of the anode-grid section. The presence of current coupling between the Lg and Lg lamps and the high input impedance of the cathode follower provide better modulation quality than with other methods of supermodulation onto the screen grid. The schematic diagram of the modulator and microphone amplifier is shown in Fig. 3. In Fig. Figure 4 shows a diagram of a modulator option for transmitters, the final stage of which has a lamp with screen grid currents exceeding 30-40 mA at 1!g above - 350 V. Setting up a transmitter for telephone operation with a modulator according to the diagram in Fig. 3 is easy. After tuning the transmitter for maximum output to the antenna in telegraph mode, the screen grid is connected to the cathode of the L lamp using a switch Pg (CLC position). By changing Ru (or changing the value of the blocking voltage) the carrier level in pauses is set. To operate in the so-called “symmetrical mode” R, set in such a position that the anode current of the lamp
RA constituted the “telegraph” current
(during modulation, 1a should reach the telegraph value if the effective value of the modulating voltage on the screen grid corresponds to Uc2 of the telegraph mode).
To obtain the supermodulation effect, the value of the “silence” current is 1 1
reduced to -- and even to -3- current 4 o
in telegraph mode. If a change in the value of R„ does not provide the indicated changes in the RA mode in the absence of modulation, the value of the resistances should be slightly reduced or /?, or /?20, the negative voltage can be slightly increased from -100 to -150 V. The degree of carrier attenuation during pauses also depends on the ratio of U& to Un of the PA lamp. The more this is related
A simple circuit of an AM HF transmitter for the amateur 3 MHz band for a novice radio amateur: a detailed description of the operation and device
Proposed transmitter circuit does not contain scarce parts and is easily repeatable for beginning radio amateurs taking their first steps in this exciting, exciting hobby. The transmitter is assembled according to the classical design and has good characteristics. Many, or rather, all radio amateurs begin their journey with just such a transmitter.
It is advisable to start assembling our first radio station with a power supply, the diagram of which is shown in Figure 1:
picture 1:
The power supply transformer can be used from any old tube TV. The alternating voltage on winding II should be about 210 - 250 v, and on windings III and IV 6.3 v each. Since the load current of both the main rectifier and the additional one will flow through diode V1, it must have a maximum permissible rectified current twice as large as the other diodes.
Diodes can be taken of the modern type 10A05 (sample voltage 600V and current 10A) or, even better, with a voltage reserve - 10A10 (sample voltage 1000V, current 10A), when using more powerful lamps in the transmitter power amplifier, we need this reserve It can be useful.
Electrolytic capacitors C1 – 100 µF x 450V, C2, C3 – 30 µF x 1000V. If you don’t have capacitors with an operating voltage of 1000V in your arsenal, then you can make up 2 series-connected capacitors of 100 μF x 450V.
The power supply must be made in a separate housing, this will reduce the overall dimensions of the transmitter, as well as its weight, and in the future it will be possible to use it as a laboratory one, when assembling structures on lamps. Toggle switch S2 is installed on the front panel of the transmitter and is used to turn on the power when the power supply is under the table or on the far shelf, where you really don’t want to reach (can be excluded from the circuit).
Figure 2:
Modulator details:
C1 – 20mkfx300v, C7 – 20mkfx25v, R1 – 150k, R7 – 1.6k, V1 – D814A,
C2 – 120, C8 – 0.01, R2 – 33k, R8 – 1m variable, V2 – D226B,
C3 – 0.1, C9 – 50mkfh25v, R3 – 470k, R9 – 1m, V3 – D226B,
C4 – 100 µFx300V, C10 – 1 µF, R4 – 200k, R10 – 10k,
C5 – 4700, C11 – 470, R5 – 22k, R11 – 180,
C6 – 0.1, R6 – 100k, R12 – 100k – 1m
Electret microphone from a cassette recorder or telephone headset (tablet). The part of the circuit highlighted in red is necessary to power the microphone; if you intend to use only a dynamic microphone, then it can be removed from the design. Trimmer resistor R2 sets the voltage to + 3V. R8 – modulator volume control.
The output transformer is from a tube receiver or a TV of the TVZ type; you can also use vertical scan transformers TVK - 110LM2, for example.
The setting consists of measuring and, if necessary, adjusting the voltages at terminals (1) +60V, (6) +120V, (8) +1.5V of the 6N2P lamp and at terminals (3) +12V, (9) +190V 6P14P.
Figure 3:
Transmitter details.
C1 – 1 section gearbox 12x495, C10 – 0.01, R1 – 68k
C2 – 120, C11 – 2200, R2 – 120k
C3 – 1000, C12 – 6800, R3 – 5.1k
C4 – 1000, C13 – 0.01, R4 – 100k variable
C5 – 0.01, C14 – 0.01, R5 – 5.1k
C6 – 100, C15 – 0.01, R6 – 51
C7 – 0.01, C16 – 470 x 1000V, R7 – 220k variable
C8 – 4700, C17 – 12 x 495, R8 – 51
C9 – 0.01, R9 – 51
R10 – 51
The GPA coil L1 is wound on a frame with a diameter of 15 mm and contains 25 turns of 0.6 mm PEV wire. The inductor in the cathode of lamp L2 is factory-made and has an inductance of 460 μH. In my design, I used a choke from a TV, wound on an MLT - 0.5 resistor with a wire in a slot winding. Chokes L3 - L6 are wound between the cheeks on old-style VS-2 resistors and have 4 sections of 100 turns of PEL-2 wire with a diameter of 0.15 mm. Chokes L7 and L8 each have 4 turns of PEV wire with a diameter of 1 mm wound on top of resistors R8 and R9 MLT-2 with a resistance of 51 Ohms and serve to protect the final stage from self-excitation at high frequencies. The anode choke L9 is wound on a ceramic or fluoroplastic frame with a diameter of 15 - 18 mm and a length of 180 mm. PELSHO wire 0.35 turn to turn and has 200 turns, the last 30 turns in increments of 0.5 - 1 mm.
The L10 contour coil is wound on a ceramic, cardboard or wooden frame with a diameter of 50 mm and has 40 turns of PEL-2 wire with a diameter of 1 mm. When using a wooden frame, it should be well dried and varnished, otherwise, when exposed to high RF current, it will dry out, which will lead to deformation of the winding and possibly even a breakdown between the turns.
C17 is a double unit from a tube receiver with plates removed through one in a movable and fixed block.
Variable resistor R4 sets the bias on the control grid of the 6P15P lamp, and resistor R7 sets the bias for 6P36S lamps.
Relays can be of any type for a voltage of 12V with a gap between contacts of 1mm with a switching current of 5A.
Ammeter for current 100 mA,
The final stage is tuned to resonance using the minimum milliammeter readings.
The bias circuit is shown in Figure 4:
Figure 4:
Transformer T1, any step-down transformer 220v/12v with reverse connection. The secondary (step-down) winding is included in the filament circuit of the lamps, and the primary serves as a step-up winding. The output of the rectifier is about -120V and is used to set the bias of the lamps of the final stage of the transmitter.
Useful thing!
The figure above shows a diagram of the field strength indicator. This is a circuit of the simplest detector receiver, only instead of headphones, it has a microammeter, by which we can visually observe the signal level when tuning the transmitter to resonance.
The CLC modulator in TLG mode applies a negative voltage to the grid of the left half of lamp L2, which turns off the lamp. In this case, a large positive voltage from resistor R1 opens the right half of L2, which ensures that positive voltage is supplied to the screen grid L1. In the case of operation in the TLF mode, the low-frequency signal arriving at the grid of the left half of lamp L2 causes a change in its anode current.
As a result, the anode current of the right half of lamp L2 and the screen voltage of lamp L1 change, which leads to the appearance of a modulated signal at the output of the transmitter. The CLC modulator practically does not require adjustment. It is only necessary to set, using potentiometer R3, the anode current of lamp L1 when silent in the TLF mode equal to 20-25% of the value of the anode current in the TLG mode. If this cannot be achieved, the bias voltage should be increased or the excitation voltage of lamp L1 should be reduced. The CLC modulator has been in use at the radio station for a long time. In all cases, the quality of modulation was assessed positively by correspondents.
