Very simple from the point of view of design, the Klopik transceiver is performed exclusively on elements of a discrete type. It is ideally suited for use in the amateur radio bands in the CW, SSB and QRP (key) modes. It has a feature called PSK. With it, you can run the transceiver as a stationary transmitting device by connecting it to a personal computer. You can even say that you get a kind of SDR transceiver.
Transceiver Features
The design has a fairly small number of elements, this can be called the main advantage of the device. And it should be noted that there are no microcircuits in the device, everything is built on transistor cascades. And this gives a huge plus - you can easily intervene in almost any part of the circuit and replace one or two transistors to increase the power of the device.
Even a novice radio amateur will be able to make a Klopik transceiver with his own hands. Moreover, it is recommended for repetition to everyone who is trying to learn the delights of radio business. The minimum number of winding elements that require adjustment, facilitates the operation of the device. Switching the transmission and reception modes is simplified to the maximum; only one relay is used. However, you can exclude it, install a button or pedal.
Features of the transceiver circuit
A very high degree of energy saving - the device can work even when the supply voltage drops to 6 V. True, only the receive path can function normally. But still, this is a huge plus when using the transceiver in travel mode. The transceiver circuit is made with one intermediate frequency. There are several types of schemes, you can use nodes with other elements in the design, there is no need to adhere to the standard.
The figure shows the Klopik transceiver. A printed circuit board can be made either manually or by means of programs for a personal computer. The diagram contains the designations of such nodes:
- The main reverse path (includes UPCH-1, UPCH-2, URC).
- Amplifier sound frequency.
- PDF
- Automatic gain control.
- Microphone amplifier
- Telegraph key.
- OG and VOX.
Looking at the diagram, you can see that there are several microcircuits in the design, but all of them are installed in the ULF unit.
Winding data of coils and transformers
A bit about winding elements:
- Broadband transformers T1, T2, T8 are wound with PEV-0.15 wire on ferrite rings with 600 N dimensions K7x4x4. The wires are slightly twisted - no more than three twists per centimeter. The total number of turns is 15..18.
- T7 on the ring K10x6x5 with the same wire, but the permeability is from 1000 N. The wire is laid in one layer and the entire space is filled.
- T3-T6 are performed on the same rings as T1, T2, T8. Also a maximum of 18 turns, but you need to make an average conclusion - the beginning of one winding is connected to the end of the second.
- L1 - winding 25 turns of wire brand PEL-0,1. 5 mm frame, tuning core type SB-9 (armored), M3 thread. Be sure to use an aluminum screen.
Reception mode
At the output of the bandpass filters, a signal appears, which is fed to the mixer, assembled on diodes. The second input of this mixer receives a signal from the GPA. For the Klopik transceiver, only classic knot circuits are used. Then the signal is fed to the amplifier, which is built on two transistors - VT1 and VT2. A quartz filter is used as a cascade load . With its help, the selectivity of the receiving part along adjacent channels is ensured.
Then the signal goes to the second stage of the amplifier, which is also performed on two transistors - VT3 and VT4. The second quartz is used as a load. Then the amplified signal is fed to another stage of the amplifier, which is made on transistors VT5 and VT6. And only after it on a ring mixer, built on diodes. A signal is generated at the same mixer, which is produced by a reference quartz oscillator (assembled on a VT10 transistor).
AGC and ULF
A low-frequency signal (sound) is already taken from the mixer output. And it is fed through a relay to an ultrasonic scanner, which in the classical circuit is assembled on a chip like LM386. This is a common chip that is used in various amplification equipment. She has very good sensitivity, low noise, high gain. To adjust the volume at the input of the amplifier, a resistor R32 is installed.
The output is a simple headset for a personal computer with two speakers. The automatic gain control circuit is built on:
- Capacitors C24 and C28.
- Diodes VD9 and VD10.
- Resistor R26.
- Transistor VT9.
The AGC scheme is very simple, but it has high efficiency, it allows you to quite comfortably listen to the signals of radio stations with an air noise level up to +40 dB (judging by the S-meter).
The AGC starts to work only signals with a strength of more than 7. Even weak radio stations are easily βreadβ. In the design of the S-meter, a current amplifier is used, made on the VT11 transistor - a microammeter is connected to its output, which has a current of the largest deviation of 200 ΞΌA.
Transmission mode
Please note that a special kit can be purchased for production. The Klopik transceiver has one feature - all the cascades of the UHF that are present in it are reversible. They operate in both receive and transmit mode. The original design uses three electromagnetic relays, indicated on the K1-K3 circuit. The relay contacts K1.1 change the direction of the signal along the stages of the amplifier.
But the contact group K3.1 supplies voltage to the microphone amplifier. At the same time, the UPT, ULF and S-meter are turned off. Now the signal moves along this chain:
- From a microphone amplifier, which is assembled on transistors VT7 and VT8 through the contacts of the relay K2.1 to a ring-type mixer, assembled on semiconductor diodes. At the same time, the mixer works as a balanced modulator.
- Further, the signal for which the carrier is suppressed passes through three stages of the IF amplifier. With the help of two quartz, the necessary sideband is highlighted. This means that an SSB signal is being generated.
- Using a mixer made on semiconductor diodes VD1-VD4, the signal is transferred to the carrier frequency. The DFTs used in reception and transmission are the same.
The carrier can be suppressed in the balanced modulator using the trimmer resistor R20. Sometimes, for deep suppression, additional trimming capacitors are installed (in parallel to the already mounted ones).
The article presented an image of the printed circuit board of the Klopik transceiver; its circuit diagram was considered as detailed as possible. It should be noted that transistors in the high-frequency part can be used more powerful in order to achieve maximum radio range.