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The frequency Converter, whose scheme is shown in Fig. 1, provides a high dynamic range of the transceiver. It consists of two keys on the diodes V4-V11 included in a bridge circuit, and a management node. The connection between the management node and the keys of the transformer (T1).

The Elements Of D1.1 and D1.2 of the sine wave oscillator form rectangular pulses with a slope rate of no more than 2 NS. These pulses are amplified by the differential amplifier transistors V2, V3. Converter balance resistor R1, which determines the equality of the durations of the positive and negative control pulses. Transformer T1 is designed with short turns, provides connection of the amplifier with a diode-keys with minimal distortion of the control pulses. Resistors R12-R15 limit the maximum current through the public key, and the incident voltage, which is inverse diodes for the private key determines the maximum input amplitude of the transformed signal. Obviously, the input and output of the Converter vzaimoobratima. Ground the inverter input DC voltage is not required.


Fig.1

This Converter was tested as a mixer of a receiver with a low noise channel gain of the inverter and an Electromechanical filter at the input. Harmonization of the output of the mixer c EMF provided the transformer. As a local oscillator used a crystal oscillator to a frequency of 5.2 MHz, the following results were obtained.
Sensitivity with respect to signal/noise ratio of 10 dB was 1.8 mV. The level of the converted signal fell by 1 dB when the interfering signal is located outside the bandwidth of the path of the drive, reached 1.6 V (RMS).
The level of intermodulation components of the 3rd order (according to the method described in the magazine "Radio", 1981, No. 3) was not more than -100 dB. The last parameter can be improved by 6 to 10 dB, using the if filter low loss, such as quartz and an if amplifier with high sensitivity.

In a differential amplifier, it is desirable to use transistors with the same ratio h21e. Transistors CTA can be replaced by KT368 with any letter index. Instead Of D1.1 and D1.2 you can apply the logical element "OR NOT" series C or K100 with any number of inputs. If the driver control pulses will be used fast trigger, the frequency of the local oscillator should be twice the desired. Balancing is performed automatically.


Fig.2

The case of transformers T1 and T2 with short turns (see Fig. 2) brass, preferably with a silvered surface. Along it is made of longitudinal cuts for the conclusions. All windings are made on a separate annular magnetic cores of ferrite MNM (size To HH,5). The windings are insulated from the core varnished cloth or PTFE tape. Winding I at T1 and T2 contains 10 turns (removal from the 5th round), winding II - 5 turns of wire PELSHO 0,12 uniformly distributed on the ring. Data are shown for the frequency range local oscillator (lo) 2...30 MHz (for lower frequencies the number of turns must be increased), the output impedance of signal source and load impedance for the transmitter must be within 50...75 Ohm. All resistors in the inverter - MLT-0,125, capacitors - K. M-6.

Mounting the inverter must comply with the best symmetry and careful screening. The supply chain must have a high frequency isolation. These measures are needed to reduce the radiation at the frequencies of the harmonics of the local oscillator.

Authors: V. Drozdov, UA3AAOJ, S. Zhukov, UA3ACV, Moscow; Publication: N. Bolshakov, rf.atnn.ru