The idea for a tube transceiver was borrowed from a foreign magazine. In the magazine of the English QRP club SPRAT No. 67, a diagram of a direct conversion tube receiver was published. Having assembled it and made sure it worked perfectly, I converted this receiver into a transceiver. It is so easy to set up that even a novice radio amateur can assemble it from “junk”, which is usually always at hand.
The high-frequency amplifier is assembled on lamp L1. From it, through circuit L4 L5 C9, the signal is supplied to the mixer, made on lamp L4. From this mixer, the low-frequency signal through the C18 R11 C19 filter goes to the ULF, made on L7. The HF and LF gain can be adjusted using potentiometers R5 and R16.
The local oscillator is assembled according to an inductive three-point circuit on lamp L2. Circuit L3 C3 C2 is tuned to a frequency half as low as the operating frequency, the second harmonic is allocated to circuit L6 C7.
The driver on the L5 lamp amplifies the local oscillator signal to the value necessary to drive the output stage on the L6 lamp to 10 watts.
The transceiver operates in half duplex, i.e. To switch to transmission mode, just press the key. In this case, the cathodes of lamps L5 and L6 are grounded by direct current through the reed switch G1, which will also ground the receiver antenna.
A transceiver that is correctly assembled from serviceable parts does not require adjustment. It is only necessary to set the circuit frequencies using GIR or some other method. When excitation of UHF, resistor R4 is selected. If the ULF gain is insufficient, an electrolytic capacitor with a capacity of 5 - 10 μF is connected in parallel with R19. If you will be working on several ranges, then capacitor C* is selected so that there is no noticeable difference in sensitivity when moving from one range to another.
This transceiver does not use a dedicated frequency offset circuit for RX/TX. This shift occurs automatically due to the difference in the capacitances of the L5 lamp on and off. In my version, the RX/TX offset was 200 - 300 Hz on 160 and 80 meters and almost 1000 Hz or more on 28 MHz.
As lamp L1 you can use 6Zh2P, 6Zh38P, 6Zh9P, 6Zh8. The best tube for a local oscillator is 6Zh2P. But 6Zh1P, 6Zh38, 6Zh9P, 6Zh7, 6Zh8 also work with worse results. Instead of L3, you can use any other lamp or semiconductor zener diode for a voltage of 100 - 150 V. The best lamp for mixer L4 - 6N2P, but you can also use 6N1P, 6N14P, 6N15P. You can use 6P9 as an L6 lamp. You can also use powerful tetrodes without an antidynatron grid by switching the antenna in RX/TX mode using a relay. A 6N1P will work well in a low frequency amplifier (L7).
1 - The coils are made of MLT-2 resistors with a resistance above 100 kOhm, wound along the entire length;
2 - The coils are made of VS-2 resistors with a resistance above 100 kOhm;
* - Above - number of turns, below - winding length in mm;
L1 is wound on top of L2, L4 is wound on top of L5;
L1 and L4 make up about 30% of the turns from L2 and L5, respectively;
The reed switch used was 30 mm long and 3.5 mm in diameter. 300 turns of PEL-0.1 wire were wound on it.
If your antenna is not constant, then constant capacitors C31 and C32 must be replaced with variable ones. In this case, the dimensions of the transceiver will increase. All blocking capacitors were of the SGM type. Circuit and transition capacitors type KT. Capacitors C28, C29, C30 type MBM.
The transceiver was assembled on a chassis made of double-sided fiberglass with dimensions of 200 x 240 x 40 mm. The spatial position of the parts coincided with their position on the diagram. Removable inductors made on sockets from octal series radio tubes made it possible to quickly change the range. The installation of radio elements was carried out using a hinged method.
When replacing C31, C32 with variable capacitors, installing a measuring device in the anode circuit of the L6 lamp, the dimensions of the transceiver will increase, but it will become more convenient to work.
When changing band coils, do not forget to disconnect the anode voltage from the transceiver!
Yu.V. Demin, UR5MMJ
Given below direct conversion transceiver made according to a direct frequency conversion scheme and is intended for SSB and CW radio communications in the 1.8 MHz range. A distinctive feature of the circuit is the use of active filters in the ULF receiver and microphone amplifier, which improve selectivity and reduce the spectrum width of the emitted transceiver signal. Transceiver parameters Sensitivity of the receiving path is at least 2 µV
Bandwidth of the receiving path in terms of level – 3 dB 2.5 kHz
Suppression of non-working sideband during reception and transmission of at least 35 dB
Carrier suppression no less than 40 dB
Output power 10 W
Supply voltage 12 V (stable)
To eliminate 50 Hz interference, the power supply is assembled in a separate housing. An inductive three-point circuit was used as a GPA (VT9) (Fig. 1). The operating frequency of the GPA is adjusted by capacitor C5.2 from 7320 to 7720 kHz. From the output of the source follower (VT10), the heterodyne voltage is supplied to the TTL level generator (VT11, DD1), after which it is supplied to a digital phase shifter - frequency divider by 4 (DD2). The DD3 multiplexer switches the phase shifter channels 0 and 90° with each other during the transition from reception to transmission. Heterodyne signals from the outputs of the multiplexer are supplied to the engines of the balancing potentiometers (R9, R10) of the mixer.
The transceiver's RF amplifier is assembled on a field-effect transistor VT1. The RF gain is adjusted by variable resistor R1, which changes the bias voltage at the second gate of the transistor. The input circuit of the RF amplifier is adjusted with capacitor C5. i within a range of 160 m. The output circuit is low-Q, broadband. From it, the signal is fed through the communication coil L3 to the mixer transformer. Diode VD3 prevents the circuit L2, C12 from being bypassed by transistor VT1 when switching to transmission mode.
In a single-way mixer, a well-known circuit based on T-bridge RLC links is used as a low-frequency phase shifter. From the output of a single-band signal mixer, a low-frequency filter is supplied through a two-stage low-pass filter.
In the ULF, after the preliminary amplification stage, a fourth-order active filter (DA1) is used, which further increases the selectivity of the receiving path. In CW reception mode, an LC circuit is connected in parallel with the volume control. The ULF DA2 output microcircuit operates in a lightweight mode for a 100-ohm load.
The microphone amplifier of the transmitting path also contains an active filter. The output of the active filter is loaded onto the source follower (VT8). The function of diode VD11 is similar to that of VD3. For the CW mode, a separate tone generator (VT5) is used in the transmitting path. During transmission, the audio signal from the output of the microphone amplifier is fed through a low-pass filter to a single-sideband driver. From the output of the SSB shaper, the signal is fed to the transceiver's power amplifier. The transceiver's power amplifier is three-stage. The final stage is assembled using a VT15 transistor according to a circuit with a grounded collector. From it, the signal goes to the P-circuit, and then through capacitors C89, C90 and contacts K1.1 of the antenna relay to the antenna. The cascade on VT16 provides a “self-listening* mode when working with a telegraph.
Transceiver design. The transceiver is located on 6 boards (Fig. 2):
board 1 – GPA digital phase shifter, switch for channels 0 and 90″, power supply for TTL microcircuits; board 2 – URCH;
board 3 – single-band mixer and passive low-pass filter; board 4 – ULF;
board 5 – microphone amplifier and 1 kHz generator; board 6 – preliminary stages of the transceiver power amplifier.
Boards 2 and 6 are located in the basement of the transceiver chassis. The power amplifier is placed in a separate shielded housing with a partition between the preliminary and final stages. All connections between the boards, except for the power wires, are made with shielded wire, and the RF circuits are made with coaxial cables.
The most critical components of the transceiver are the VFO and the single-band mixer. Particular attention should be paid to the design of the VFO circuit, since the stability of the transceiver frequency depends on it. The VFO frequency drift should not exceed 100 Hz per hour after warming up the transceiver for 10 minutes. The VPA coil is wound on a ceramic tube with a diameter of 6 mm and a length of 15 mm. As a frame
The coil uses a CBG capacitor housing. To do this, the capacitor should be unsoldered and the contents removed. Then use a file or sandpaper to cut the fastening rings. They will be the contact points for the IZ winding. To wind the coil more tightly, it is necessary to solder the tap first. After this, with tension, turn to turn, wind the coil, and solder its ends to the contact points. On top of the coil, with epoxy glue, you need to glue a textolite or other threaded sleeve, for example, from the IF circuits of pocket receivers, into which you screw a standard 600NN ferrite core. Place the GPA circuit in the screen.
Capacitors C76-C78 are soldered directly on the back side of board 1 between the positive and common terminals of each of the digital microcircuits DD1-DD3. Capacitor C72 is located near the collector of transistor VT12. Such measures make it possible to completely avoid RF radiation through the power circuits of microcircuits. Interference can be audible during reception in the form of noise or hum with a certain sampling when adjusting the GPA.
The mixer coils L6, L9, L10 are wound with a wire folded in half, after which the beginning of one winding is connected to the end of the other winding. This tap is the midpoint of the coils. The winding data of the transceiver coils are given in Table 1. The standard size of the rings of all coils, except for the low-pass phase shifter coils 19, L10 and low-pass filter coils U1, L12, can be changed in any direction. Options for possible replacement of parts used in the transceiver are given in Table 2. The RES-47 relay is used as an antenna switch, but any relay with a low contact capacitance is suitable.
The transceiver has separate high-frequency and low-frequency paths for reception and transmission; common to both modes are a mixer-modulator and a smooth range generator.
The smooth range generator (VFO) is made on two field-effect transistors VT5 and VT6 with source coupling. It operates at a frequency equal to half the frequency of the received or transmitted signal. When operating for reception and transmission, the output circuits of the GPA are not switched and the load on the GPA does not change. As a result, when switching from receiving to transmitting or vice versa, the VFO frequency does not deviate. Adjustment within the range is carried out using a variable capacitor with an air dielectric SJ, which is part of the GPA circuit.
The transceiver is designed to transmit and receive SSB and CW in the 28-29.7 MHz range. The device is built according to a direct conversion scheme with a common mixer-modulator for reception and transmission.
Specifications:
In SSB transmission mode, the signal from the microphone is amplified by operational amplifier A2 and fed to a phase shifter using elements L10, Lll, C13, C14, R6, R7, which provides a phase shift of 90° in the frequency range 300-30-00 Hz.
In the L4C5 circuit, which serves as the general load of the mixers on diodes VD1-VD8, the upper sideband signal is allocated in the range of 28-29.7 MHz. The L6R5C9 high-frequency wideband phase shifter provides a 90° phase shift in this range.
The selected single-sideband signal is fed through capacitor C6 to a three-stage power amplifier using transistors VT7-VT9. The stage of pre-amplification and decoupling of the output circuit of the mixer-modulator is made using a VT9 transistor. The high input impedance combined with the low capacitance of C6 ensures minimal impact of the power amplifier on the C5L4 circuit. The VT9 collector circuit includes a circuit configured to the middle of the range. The intermediate stage on the VT8 field-effect transistor operates in class B mode, and the output stage operates in class C mode.
The U-shaped low-pass filter on the C25L13C26 cleans the output signal from high-frequency harmonics and ensures that the output impedance of the output stage is matched to the characteristic impedance of the antenna. Ammeter PA1 is used to measure the drain current of the output transistor and indicates the correct settings of the P-circuit.
The telegraph mode is ensured by replacing amplifier A2 with a sinusoidal signal generator with a frequency of 600 Hz (Fig. 21). Switching CW-SSB is done using switch S1. The telegraph switch controls the bias of VT11 of the generator preamplifier and, therefore, the supply of a low-frequency signal to the modulator.
In receive mode, 42 V power is not supplied to the transmitter stages, and the power amplifier and microphone amplifier are turned off. At this time, a voltage of 12 V is supplied to the stages of the receiving path.
The signal from the antenna enters the input circuit L2C3 through the coupling coil L1; it matches the loop impedance to the antenna impedance. The transistor VT1 is used for AMP. The gain of the cascade is determined by the bias voltage at its second gate (divider across resistors R1 and R2). The load of the cascade is circuit L4C5, the connection of the RF cascade with this circuit is carried out through the communication coil L3. From the coupling coil L5, the signal is supplied to a diode demodulator using diodes VD1-VD8.
Coils L8, L9 and a phase shifter on L10 and L11 highlight signal 34 in the frequency band 300-3000 Hz, which is fed through capacitor C15 to the input of operational amplifier A1. The gain of this microcircuit determines the basic sensitivity of the transceiver in receive mode. Next comes amplifier 34 on transistors VT2-VT4, from the output of which signal 34 is sent to small-sized speaker B1. The reception volume is adjusted using a variable resistor R15. In order to eliminate loud clicks when switching “reception-transmission” modes, power is supplied to the UMZCH on transistors VT2-VT4 both during reception and transmission.
Most of the transceiver parts are installed on three printed circuit boards, sketches of which are shown in Fig. 22-24, On the first board there are parts of the input RF receiving path (on transistor VT1), parts of the mixer-modulator with phase-shifting circuits, as well as parts of the local oscillator. The second board contains low-frequency stages on microcircuits A1 and A2 and transistors VT2-VT4. The third board houses the power amplifier of the transmitting path.
The board with the mixer-modulator, RF amplifier and GPA is shielded. The “reception-transmission” modes are switched by a pedal, which turns on and off the 42 V voltage and controls two electromagnetic relays, one of which switches the antenna, and the second supplies 12 V voltage to the receiving path. The relay windings are powered by a voltage of 42 V, and in the de-energized state the relay contacts switch on the receiving mode.
To power the transceiver, a basic stationary power supply is used, from which a constant stabilized voltage of 12 V with a current of up to 200 mA and a constant unstabilized voltage of 42 V with a current of up to 1 A are supplied.
Winding data of transceiver coils Table 4
The transceiver uses fixed MLT resistors for the power indicated in the diagrams. The adjusted resistor is SPZ-4a. Loop capacitors are necessarily ceramic, tuning capacitors are KPK-M. Electrolytic capacitors - type K50-35 or similar imported ones. Variable capacitors of the local oscillator and output circuit are with an air dielectric.
To wind the contour coils of the URCH, mixer and transmitter, ceramic frames with a diameter of 9 mm with tuning cores SCR-1 are used (plastic frames from the UPCH paths of old tube TVs are also possible, but their thermal stability is much worse than that of ceramic ones). Low-frequency mixer-modulator coils L8 and L9 are wound on ring cores K16x8x6 made of 100NN or higher frequency ferrite (100HF, 50HF). Coils L10 and L11 are wound on OB-ZO frames made of 2000NM1 ferrite. The coils of erasure and magnetization generators of semiconductor reel-to-reel tape recorders were wound on such cores. The winding data of the transceiver coils are given in table. 4.
KPZZG transistors can be replaced with KPZOZ with any letter index or with KP302. The KP350A transistor can be replaced with KP350B, KP350V or KP306. Transistor KP325 - on KT3102. Power field-effect transistors KP901 and KP902 can be with any letter indices. Any silicon and germanium (respectively) transistors of the appropriate structure are suitable for UMZCH. Diodes KD503 can be replaced with KD514, and diode D9 with D18.
Literature: A.P. Family man. 500 schemes for radio amateurs (Radio stations and transceivers) St. Petersburg: Science and Technology, 2006. - 272 pp.: ill.
Direct conversion transceiver for 10.116/10.113 mhz “Priyatel-8”.Brief introduction.
I quickly began assembling the direct conversion transceiver “Priyatel-8”, the fact is that I most likely will not have the opportunity to assemble some kind of structure until late autumn. And, according to my criteria, in order not to turn into a lover of “talk”, wandering around numerous forums, you need to collect at least 2 completed structures per year. Simple, very simple, but in the form of a complete design and fully operational, preferably according to a relatively original design. At one time, the QRP club organized a homemade competition at an in-person meeting, a useful event!
By the way, the 5th month of this year is already ending. There was little free time, so I had to work as quickly as possible.
Checking "Prijatel-8" on the air.
30.05.2010.
The construction was completed a couple of days ago, but was not tested on air, in the forests and fields, continuous rains! It’s clear that I’m “sitting on pins and needles,” but nothing can be done. Rain and +9 in the morning and almost until lunchtime on May 30, 2010. However, around lunchtime, enlightenment began to emerge! It doesn’t take long for me to get ready: I put the battery, “Prijatel-8”, phones, key and antenna in my bag and off I go!
It's wet, but it's not raining, at least not yet. And I quickly move forward. No, not to the height of 109.0, for which the antenna is intended, by the time I get there, it will start raining again. I move to a high-rise, where I work QRP/p, when there is no time to move to a greater distance.
The acacia blossomed.
The mountain ash is also not far behind, it has bloomed.
Thorough wind at high altitude.
The antenna must be temporarily suspended in its working position.
I am a supporter of normal, full-size antennas fed via coaxial cable. In this case, it is a dipole for 10 MHz. 
I hook my right shoulder to a tree, fortunately the cord is already thrown there and all that remains is to hook the cord to the insulator. I dig the central pole to which I tie the central insulator of the dipole shallowly into the ground.
It became more fun, the right arm of the dipole is in working position.
Likewise, I dig a hole for the left pole.
A little to the left, in the plane of the antenna, I hammer a peg into the ground, behind which the antenna guy will be fixed.
I wrap the guy around the pole, lift it, dig it in with earth and tie the cord around the peg.
This all happens quite quickly.
Here is the photo of the left arm of the dipole.
Dipole in working position. 
>The passage today is very disappointing. Stations on the bands do not make noise, with the exception of biggans. RD9CX.
If Sergei says that the passage is unimportant, then it is so.
But let's hope. For quite a long time I transmitted CQ de UA1CEG/p to 10113, silence, no one.
I switch to 10116 and there is a QSO! And what a great one!
With QRP station! I didn't count on such luck. The transceiver works great, I obviously overestimated the 9A0QRP report. To celebrate, quite understandably, I suppose.
Returning to reality... The wind is driving a suspiciously dark cloud! You need to leave quickly. I am dismantling the dipole, not without regret. He looked at the prepared fire pit:
No, the planned leisurely tea party is postponed, the cloud is approaching and growing menacingly in size.
I pick up a pace of 120 steps per minute and return home. However, the cloud passed Garbolovo without stopping, so... a few drops fell, but in our area this is not considered rain. But you can’t guess, you don’t want to get wet, and the transceiver test went great!
The transceiver perfectly receives on long LW, 80 meters, without the appearance of broadcasting stations, this is also very cool!
Receiver.
Direct conversion receiver, assembled according to a simple circuit, works like a direct conversion receiver, assembled according to a simple circuit.
There is no need to make unfounded claims to a device of this class. At the same time, a properly adjusted simple PPP has very high characteristics. The performance characteristics of this device, considering such minimal labor and component costs, are excellent!
Any complications, with the aim of dramatically improving the characteristics, first of all, sharply increase the costs of labor, time and components, negating the main advantage - the extreme simplicity of the device. A superheterodyne of a similar class, with an improved SPP, will require significantly less effort, with higher performance.
If, on a simple PPP, interference from broadcasting stations at 7 MHz will be heard in a double band, then if phase demodulation is applied, the same interference will be received, only in one band. But, interference will occur and phase demodulation will not help. Of course, if you apply a lot of effort, you can at least reduce interference leakage.
This is for enthusiasts and originals... Personally, I would prefer, with much less effort and with better results, to assemble a superheterodyne.
Work begins:
Sockets: “Phone”, “Key”, connectors: “+12 volts” - 2 pcs., “Ant TX”, “Ant RX”. Clamp: "Body". That's all.
We install the necessary terminals, connectors, etc. If the shortwave operator does this, then that’s it, he will have a device! Empty talk ends when the tasks of this stage are completed. Only at the keyboard, questions arise one after another, as soon as specific work begins, that’s it, no questions (chatter!).
The main block of PPP ULF. 
This is the best ULF option, tested in real designs, during real operation on the air. Setting up the ULF is simple; you need to select the values of R3 and R4 so that the voltage at the collector of the third transistor is equal to half the supply voltage, 6 volts in this case.
I think it is clear that the same circuit can be assembled on the famous ones: P27, P28, MP39B, MP40, P15, etc. change the polarity of the power supply and electrolytic capacitors and that’s it, the rest is the same.
The photo shows the assembled ULF.
At the risk of being again accused of “not publishing the complete circuit!”, I believe that this block diagram is more than enough, taking into account the detailed photos and detailed diagram of the ULF and local oscillator.
It’s hard to imagine a shortwave operator who is not able to assemble the PPP according to this description and numerous photographs, but... you never know what happens, probably my message is simply not for him. I still hope that a radio amateur will be able to connect the microcircuit to the input circuit, supply power to the microcircuit and connect the transformer...
Whoever collects will collect.
Popular wisdom: “The one who walks will master the road!” 
The ULF is built into the housing and a tuning capacitor is added to adjust the input circuit.
We assemble the mixer 235PS1 (NE602, NE612, etc.). We connect a matching transformer from a radio receiver, or any suitable similar one, to the mixer.
Photo of the working moment - setting up the local oscillator. At this stage, you need to see how active the quartz you have is, and you may have to provide an emitter follower to reduce the load on the local oscillator. Here everything is decided realistically, practically.
Input circuit. For microcircuits with a symmetrical signal input, for example NE602, NE612, a 3-turn coupling coil is simply wound (the quantity is specified practically) and connected to the corresponding inputs. I do not accept connecting an unbalanced output to the balanced input of a mixer.
Some clarification is required here.
This version of the circuit can provide receiver sensitivity that is absolutely redundant; it simply cannot be implemented. And reducing the connection with the circuit sharply increases the dynamics, the quality factor of the circuit will be very high, which will have a positive effect on selectivity. For now, the presence of interfering broadcast stations, and this is the scourge of PPP, could not be detected at all. And this is when connected to a full-size delta. Of course, final adjustments will be made after a real check of the forests and fields on the air.
Please note that the circuit is of high quality, on a frame made of ribbed HF ceramics, and the tuning capacitor is made with an air dielectric. That is, the quality factor of the circuit is high, which is fundamentally important for the high-quality operation of the device. No Chinese cardboard frames for coils, low-quality capacitors, etc. "modern components". The device is being assembled for on-air operation .
A mixer based on back-to-back-parallel connected diodes shunts the circuit and is completely inferior to this option, without any options. Practically tested. Of course, if you make a completed design, for practical use.
Of course, no one will forbid you to assemble something on a circuit board and, without false modesty, consider yourself an expert in direct conversion technology.
The photo shows the first station heard on the air on this device, when using a soldering iron as an antenna. This is RZ6MM, 21.03 MSK 20.05.2010. But, this is on the 4th floor, in stationary conditions. But still, quite decent.
At this point, I decided that there are doubts about the activity of the quartz and it is better to add an emitter follower. This is also determined practically.
On the 7030, for example, an emitter follower was not needed.
This completes the assembly of the receiving part of the transceiver. Some adjustments may be made during operation, or nothing may be needed. It will probably be possible to increase sensitivity, given the extremely low level of interference in nature, away from populated areas. Let me remind you that in this version the gain margin is very large and sensitivity better than 1 µV is obtained without the slightest difficulty.
Transmitter.
It is known that transistors have a low-impedance output impedance, which creates certain difficulties in matching the low-impedance output of the transmitter with the relatively high-impedance input of the antenna, and some antennas simply have a high-impedance input. You have to painstakingly match the P-circuit at the output of the transmitter, which often requires a lot of effort, otherwise
and the introduction of a two-link P-circuit.
I decided that assembling the so-called “binoculars” - a matching broadband RF transformer would require much less effort and would ensure load matching over a wider range.
The technology is simply ridiculously simple: a piece of shielded wire, for example, a coaxial cable, is cut off, the braid is removed, 6-8 rings are put on and 4 turns of relatively rigid single-core wire are pulled. Stranded is also possible, but it is flexible and more difficult to stretch.
Of course, if you want, you can do it better, using copper tubes... In our case, a simplified version will do just fine. Aesthetes can solder the screen and get hard tubes, which will be more solid. I simply don't have time for such long work. And this option, as practice has shown, works great.
The braid (this is the “primary” winding) is connected to the collector circuit of the output transistor, and from the “secondary” winding the signal is supplied to the P-circuit. 
The work went on “on the march”, so on a piece of paper I sketched what I had used in the transmitter, so as not to forget later.
I hope I won’t offend anyone if I point out that the broadband “binoculars” transformer is placed on a platform made of plexiglass or other dielectric, not directly on the board.
Here is the photo of the transmitter. It doesn't look scary at all, does it?
Meanwhile, without “binoculars” I fiddled and fiddled... I couldn’t really match the transmitter with a 75 ohm load! I have a KT920A installed in the pre-final stage, which is a clear luxury, but I have run out of KT610.
I don’t like the KT911 that are available, because of their tendency to self-excite, the KT603 is somewhere, but I haven’t found it.
Pay attention to the zener diode chain (D816, in this case) in series with the RF diode (KD503, in this case), this chain is visible in the photo.
This chain should protect the transistor from breakdown by high voltage, for example, you hooked your foot on the antenna or cable and disconnected the antenna from the antenna socket. As a rule, this leads to instant breakdown of the transistor.
A zener diode-diode circuit, designed for a voltage below the maximum permissible voltage of a given transistor, reliably protects the output transistor.
And the large area of the cooling surface reliably protects the transistor from thermal failure; in this case, the transistor is securely screwed to the housing. It is doubtful that the battery capacity will be enough to heat the case to the maximum permissible temperature for a given transistor, and you will indifferently observe this lengthy process.
The output signal has the shape of a regular sinusoid in a very wide change in load (active, finite resistors 75 ohms and higher) - from 37.5 ohms - in parallel 2 resistors of 75 ohms (did not load below) to 500 ohms. When the load is turned off, the sine wave is also correct. Obviously, the merit of the “binoculars” is in the normal operation of the transmitter, when the load changes within a very wide range.
I do not indicate the frequency change capacity, because they are selected individually for a specific quartz specimen. If quartz provides a much longer tuning area, then you can generally install a switch and provide several operating frequencies, in this case there are 2 of them.
If desired, you can provide an emitter follower between the quartz local oscillator and the pre-terminal amplifier, but this is rather a reinsurance. But, if the quartz is not very active, there are doubts, it is better to provide an emitter follower. This will not cause you too much trouble and expense. 
Working moment - connected the light bulb. In reality, the light bulb does not glow as brightly as the camera perceives it.
Self-control.
Self-monitoring in a direct conversion transceiver is not a routine task at all.
Of course, if you put a toggle switch (button, pedal) “receive-transmit”, then there is nothing to talk about. But, I want without buttons, toggle switches, pedals - press the key and you’re on the air.
Connect a multivibrator generating a frequency of 600-800Hz to the ULF. I pressed the key and a signal was heard in the ULF. Elementary, isn't it? Elementary, if it is not a hardware device, but an imaginary, fictitious one. You connect... but the quality is not so great, and it also works differently on different antennas. It wheezes, it's just annoying.
Oleg Viktorovich RV3GM also spoke about the difficulty of organizing high-quality self-control in the Chamber of Commerce and Industry, and he is a recognized practitioner in the direct conversion technique.
In the end, I built in a capsule connected to a multivibrator and decided that this, if not the most optimal, was still a solution: 
There was free space. Let the capsule work. I didn't drill any holes in the lid, the volume was sufficient. Maybe in the forest, when there is a strong wind, it will be a bit weak to hear, then you will have to make changes. But it's unlikely.
The photo shows “creative chaos”, the stage of completing the transceiver assembly.
This will not surprise the soldering radio amateurs at all.
The so-called front panel. I always install LEDs; they signal the device is turned on and bring the device to life. The second LED reflects the manipulation of the transmitter:
The most “ceremonial” type of the “Priyatel-8” transceiver:
This transceiver will have to work in forests and fields, in different weather conditions, be subject to shocks and other mechanical influences, be exposed to rain, fog to be sure, work in the cold, etc. That's why I always photograph devices before field testing begins. The appearance of this device will never be better, even the body will be scratched and the covers will be dented.
There is nothing to say about pieces of paper with inscriptions; they will have to be updated several times.
05/28/2010 transceiver completed. It took a while no terms:
"weekend design"
I don't admit it.
1. About transistors.
In general, all the detailed explanations are in my messages... But, you need to look through several messages.
I will try, at least briefly, to give an explanation, and those interested can look in detail in previous detailed messages in the archive of the RU QRP club.
So, about my favorite MP101, P28, etc. Why not KT3102, KT3107, etc., or imported consumer goods?
In ULF PPP, it is most advisable to use cascades with direct connections; any additional transition capacitors introduce additional noise, phase distortion, etc.
ULF in direct conversion technology is the main amplification element and must have a very high gain.
Let's say Ku = 50,000. I believe that no one expects, by applying 1 volt of voltage to the input of the amplifier, to receive 50,000 volts at the output?
The reference literature states: “Current transfer coefficient in mode small signal
" As the input signal level increases, the ULF gain will decrease, until the ULF is blocked.
ULF on high-frequency transistors will have a very wide bandwidth; when the signal of its local oscillator leaks into the ULF input, the gain will decrease, until it is turned off.
The MP101 has a cut-off gain frequency of 0.5 MHz (!!), which is ideal for a direct conversion receiver (transceiver). Of course, RF transistors can also be used, but it is very likely that they will self-excite in the microwave and reduce the gain due to leakage of the signal from their local oscillator. Self-excitation is easily detected with an oscilloscope. But elimination, sometimes, requires a lot of effort, up to the need to replace the transistor(s)!
There is no point in using RF transistors; it is only fraught with unnecessary problems; often blocking capacitors do not help eliminate self-excitation. Personally, if I have specialized low-frequency transistors, I avoid using high-frequency transistors in ULF.
Now about the use of “tape” capacitors, such as MBM.
Again, modern, beautiful, elegant ceramic capacitors often begin to work in the ULF not as capacitors, but like quartz, they begin to generate hundreds of kilohertz HF.
The prospect of choosing non-generating capacitors does not appeal to me at all!
Here the photo shows a sine wave generated by a very modern, very elegant capacitor. There are no problems with the “ribbon” capacitor!
The microcircuits contain RF transistors, and the leakage of the local oscillator signal to the input will reduce the gain, even to the point of blocking the microcircuit.
Everyone, probably except me, loves the LM386, which makes noise like a primus stove, requires serious consideration of protection from HF interference, eats significantly more, and has a gain significantly lower than the ULF tested in “battles and campaigns” on domestic MP101, MP103 and etc. These transistors work flawlessly in TPP and at -30 degrees.
So: I use MP101, MP103, in this case, not out of originality, not because of: “ ^
This modern element base is NOT interesting
.", A
due to the fact that this is the best option, actually tested in assembled structures, which were actually tested on air, moreover, in forests and fields, under various weather conditions, even down to brutal frost!
I don’t want to create difficulties for myself by using “modern components” and then overcome them! This is not for everyone
…
2. About microcircuits.
Regarding the use of microcircuits... I have a number of imported microcircuits (TNX DL7PGA, Vladimir is my constant friend... and opponent.) I prefer domestic 235PS1 rather than NE602. Although, objectively, these microcircuits are approximately the same class. Domestic ones are less noisy and have a metal screen, which eliminates extraneous interference directly onto the chip body (NE602). And, domestic microcircuits have undergone strict selection to ensure compliance with the parameters of the specifications.
Next pair: 435UR1 and TL592. Here the domestic microcircuit is clearly superior in terms of noise, efficiency, amplification, and here the shielding of the microcircuit body is very important. All this has been tested in practice.
Also about imported microcircuits: there are a lot of microcircuits of disgusting quality, unknown manufacturer and simply non-working. Of the 3 stereo amplifier microcircuits purchased, 100% of the microcircuits had only one channel working; of course, not a single microcircuit produced the declared 20 watts of output power.
When I tried to purchase stabilizer chips, I was immediately told: “Don’t take it!” Rubbish, not workers!
Personally, I still prefer, if possible, to use reliable components. In a word, with microcircuits it is more difficult, if there is a guarantee that the microcircuits are branded, have passport specifications, that’s one thing. But if there is obvious substandard condition, unknown manufacturer, inscriptions at random, this is a completely different matter!
About domestic electrolytic capacitors.
On all kinds of forums, only a hopelessly lazy participant did not “kick” domestic components! Specially
I demonstrate domestic electrolytic capacitors: 
A box of such capacitors came into my possession at the beginning of this year, 2010. Packed, no one has put these capacitors under voltage since the moment of manufacture. 1975, by the way! I decided to check the condition of these advanced capacitors.
I parallel a dozen of these capacitors and connect them to the network through a current-limiting resistor and diode. Wonderful! No lumbago, crackling, rustling or other negative phenomena. After a while, I turn it off, take a pause, during which, as I assumed, the capacitors should be completely discharged, and short-circuit the terminals... A wire with a diameter of about 0.5 mm was broken at the moment, a mark appeared on the screwdriver, and the volume of the discharge was comparable to a pistol shot.
By the way, I had complete confidence in these capacitors and used them in the power amplifier on the GU-81M as a tribute to these glorious components. Excellent capacitors. And in parallel to them, in the PA, I soldered a resistor so that they would discharge after turning off.
The following are excellent capacitors:
Capacitors of the "ETO" brand. Manufactured in 1970 (I was in my 3rd year at that time...), this board was lying around somewhere, I don’t even remember where I got it from... Constantly, when required, I unsolder these capacitors from the board and use them. They work like new! Unfortunately, there are only 7 pieces left, the rest are in progress.
They look unpretentious, they are already about 40 years old, and they enjoy my complete trust and respect. Great capacitors!
Another board of excellent capacitors. 1989, the capacity corresponds to the rated value, with a margin, the self-discharge is surprisingly low. No similar imported ones from “Chip and Dip” even come close to matching the parameters. But, to be fair, imported ones are smaller in size. Self-discharge and drying out of imported capacitors, to put it mildly, are inferior to domestic ones... Already, judging by one topic in the forum, electrolytic capacitors have begun to dry out in “thousanders”. This is in the newest transceivers...
And all sorts of good old R-250M, M2, R-309, “Mole-M”, R-326, etc. which are over 40 years old, work flawlessly. What can we say about my R-326M, which is only about 20 years old!
Final part.
As usual, best wishes to all of us! And see you on air, including QRP/p!
73! Sincerely, UA1CEG, Yuri Alexandrov, Garbolovo village, Vsevolozhsk district, Leningrad region. LO-23,KP50FI.
Website: UA1CEG.narod.ru
With the spread of the Internet, amateur radio, unfortunately, gradually began to fade away. Where did the army of radio hooligans go, the legions of “fox hunters” with direction finders and their other colleagues... Gone, only crumbs remain. There is no mass agitation at the state level and, in general, the value system has changed - young people more often prefer to choose other entertainment. Of course, Morse code is not often used in the current digital age and radio communication in its original form is increasingly losing its position. However, amateur radio as a hobby is a cross between the romance of wanderings and considerable skills and knowledge. And the opportunity to squeak your brains, and use your hands, and rejoice in your soul.
And yet I did not disgrace my brothers,
but he embodied their forces by combining:
I, like a sailor, navigated the elements
and, like a gambler, prayed for luck.
M. K. Shcherbakov “Song of the Page”
But to the point. So.
When choosing a design to repeat, there were several requirements arising from my initial knowledge in the field of designing RF equipment - the most detailed description, especially in terms of configuration, no need for special RF measuring instruments, accessible element base. The choice fell on the direct conversion transceiver of Viktor Timofeevich Polyakov.
Transceiver – communication equipment, radio station. The receiver and transmitter are in one bottle, and they share some of the cascades.
Entry-level SSB transceiver, single-band, 160m range, direct conversion, tube output stage, 5 W power. There is a built-in matching device for working with antennas of various impedances.
SSB - single-sideband modulation (Amplitude modulation with one sideband, from the English Single-sideband modulation, SSB) - a type of amplitude modulation (AM), widely used in transmitting and receiving equipment for efficient use of the channel spectrum and the power of transmitting radio equipment.
The principle of direct conversion to obtain a single-sideband signal allows, among other things, to do without specific radio elements inherent in a superheterodyne circuit - electromechanical or quartz filters. The 160m range for which the transceiver is designed can be easily changed to a range of 80m or 40m by reconfiguring the oscillating circuits. The output stage is based on a radio tube, does not contain expensive and rare RF transistors, is not picky about the load and is not prone to self-excitation.
Let's take a look at the circuit diagram of the device.
A detailed analysis of the circuit can be found in the author’s book; there is also the author’s printed circuit board, the transceiver layout and a sketch of the housing.
Compared to the original design, the following changes were made to its execution. First of all - the layout.
The transceiver version, designed to operate on the lowest-frequency amateur band, fully allows for a “low-frequency” layout. In our own design, solutions were used that were more applicable to RF equipment, in particular - each logically complete node was located in a separate shielded module. Among other things, this makes it much easier to improve the device. Well, I was encouraged by the possibility of simple retuning to 80 or even 40m bands. There such a layout would be more appropriate.
The “Receive-transmit” toggle switch has been replaced by several relays. Partly due to the desire to control these modes from a remote button on the microphone base, partly due to a more correct layout of the signal circuits - they no longer needed to be dragged from afar to the toggle switch on the front panel (each relay was located at the switching point).
The design of the transceiver includes a vernier with greater retardation and , this makes it much more convenient to tune in to the desired station.
What was used.
Tools.
Soldering iron with accessories, radio installation tool and small metalworking tool. Metal scissors. A simple carpentry tool. I used a milling machine. Blind rivets with special pliers for their installation came in handy. Something for drilling, including holes on a printed circuit board (~0.8mm), can be contrived with one screwdriver - the scarves are specific, there are few holes. Engraver with accessories, hot glue gun. It’s good if you have a computer with a printer at hand.
Materials.
In addition to radioelements - mounting wire, galvanized steel, a piece of organic glass, foil material and chemicals for the manufacture of printed circuit boards, and related small items. Thin plywood for the body, small nails, wood glue, a lot of sandpaper, paint, varnish. A bit of polyurethane foam, thin dense foam - "Penoplex" 20mm thick - for thermal insulation of some cascades.
First of all, in AutoCAD, the layout of both the entire device and each module was drawn.
The modules themselves were manufactured - printed circuit boards, “beds” of module casings made of galvanized steel. The boards are assembled, loop coils are wound and installed, the boards are soldered into individual shield casings.
Variable capacitor for local oscillator - with every second plate removed. I had to disassemble and unsolder the stator blocks, then put everything back in place.
The body is made from 8 mm plywood, after adjusting the openings and holes, the box is sanded and covered with two layers of gray paint. The inside of the box is finished with the same galvanized steel and the final installation of elements and modules has begun.
The bib switch and the variable capacitor of the matching device are located near the antenna connector, this allows the connecting wires to be shortened as much as possible. To control them from the front panel, shaft extensions made of 6mm threaded rods and connecting nuts with stoppers are used.
The tuning vernier axis was made from a shaft from a broken inkjet printer; on the same axis there was a braking unit, which was also useful. The groove holding the vernier cable was made using an engraver.
The special pulley, the cable itself and the spring that provides tension are taken from a tube radio.
The adjustment knob is made from two large gears from the same printer. The space between them is filled with hot melt glue.
The walls of the local oscillator module are finished with a layer of polyurethane foam, this makes it possible to reduce the “frequency drift” due to heating when tuning to a station.
The telephone and microphone amplifier modules are located on the rear wall of the case; to protect it (the module) from mechanical damage, outlets are made on the side walls of the case.
Configuring the transceiver local oscillator. For it, a simple HF attachment was made for a multimeter, which allows you to evaluate the HF voltage level, for example.
Initially, it was decided to change the circuit of the output stage of the transmitter to a semiconductor one, powered by the same 12 V. In the photo above, it is not fully assembled - a milliammeter for a higher current, an additional winding on the P-circuit coil, only low-voltage power supply.
Scheme of changes. Output power is about 0.5 W.
Later, it was decided to return to the original. I had to replace the milliammeter with a more sensitive one, add the missing elements, and change the power supply.
The power amplifier module is thermally insulated from other structural elements, as it is a source of large amounts of heat. Its natural ventilation is organized - a field of holes is made in the basement of the case and on the cover above the module.
The basement of the building also contains a number of blocks and modules.
The transceiver circuit has the simplest solutions for individual components and does not shine with characteristics, however, there are a number of improvements and modifications aimed at both improving the performance characteristics and increasing the convenience of operation. This is the introduction of signal sideband switching, automatic gain control, and the introduction of telegraph mode during transmission. The suppression of the non-working sideband can also be increased somewhat by reducing the spread in the characteristics of the mixer diodes, for example, by using a KDS 523V diode assembly instead of diodes V14...V17. Improvement of individual nodes can be carried out according to schemes from. It is also worth paying attention to solutions. The applied layout allows you to do this quite conveniently.
Literature.
1. V.T.POLYAKOV. DIRECT CONVERSION TRANSCEIVERS Publishing house DOSAAF USSR. 1984
2. Diagram of an attachment to a multimeter for measuring RF.
3. Dylda Sergey Grigorievich. Small-signal SSB TRX direct conversion path to 80m
