Shortwave transceiver RW4LQ. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Shortwave transceiver RW4LQ. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Civil radio communications

Comments on the article

1. A bit of history...

The transceiver was originally "conceived" as something that could be assembled by looking into the "bedside table", although for everyone it is, of course, different in its content, nevertheless, if desired, you can find a certain set from the "domestic" element base in it , from which a “device” quite acceptable for the level of amateur radio designs will come out.

Of course, there have been no "revolutions", rather traditional "circuitry" and simplicity of design recently, the use of housing sets for radio amateurs previously produced by our enterprises, components from some industrial devices that have "served" their time ...

In general, do not judge strictly, everything was done at home, using a "gentleman's set" of tools from several screwdrivers, a dozen drills and taps, a home-made "drill gun", and, well, "handy" material left over from the time of the "Ochakov" when aluminum was not held in such high esteem as it is now ...

The printed circuit boards were made using a cutter, no etching, for this reason there are no printed circuit board drawings in the "documentation" set, alas...

(click to enlarge)

2. Main parameters (also mostly traditional)

The structure is similar to transceivers from the Ural-84, Rosa, etc. families.

- bands ..... 1.8, 3.5, 7, 14, 18, 21, 24, 28 MHz
- sensitivity of the receiving path in the SSB mode at a s / w ratio of 12 dB ..... 0.6 ... 0.8 μV
- input impedance ..... 50...60 Ohm
- selectivity ..... 70...80 dB
- output power of the transmitting path ("pressing") ..... 15 ... 20 W
- output impedance ..... 50...60 Ohm
- unipolar power supply ..... + 13.5 V
- current consumption when receiving about ..... 0.5 ... 0.6 A
- when transmitting about ..... 4...5 A
- dimensions (case from the TsSh-04 "medium" set) width ..... 240 mm
- height ..... 100 mm
- depth (without protruding handles, etc.) ..... 280 mm

... the rest can only be estimated without the appropriate equipment, you know, only approximately ...

3. Notes on the design of nodes and the transceiver as a whole

- bandpass filters "from RA3AO" - frames 12 mm;
- output low-pass filter of the fifth order, together with a relay and transistor switches ..... on a board 135x60 mm;
- the first mixer, the local oscillator signal amplifier, the diplexer, the reverse stage of the IF, the first quartz filter, the DSB amplifier ..... on a 160x60 mm board;
- the main IF of the receiver, the second quartz filter, DC amplifiers of the AGC circuit ..... on the board 160x30 mm;
- detector, filter D-3.4, preliminary and final ULF, reference local oscillator signal amplifier on a 160x60 mm board;
- amplifiers and rectifiers of the AGC circuit on the board 85x20 mm;
- RX/TX electronic switch keys on a 45x30 mm board;
- range switch on the board 60x60 mm;
- high-frequency local oscillator - circuit on the board 75x30 mm.

A coil (in a copper screen with a diameter of about 60 mm) from a radio relay station R-401 or R-405, a ceramic frame with a sputtered silver-plated bus, a silver-plated glass is also sprayed from the "hot" end of this coil (at the base, where the mount is) and into this glass a grounded cylindrical rod with a diameter of approximately 6 ... 8 mm is progressively pushed in and out, acting as a variable capacitance of the circuit. To do this, a screw mechanism is used from the mentioned radio station, at the end of which this same rod is fixed.

The slowdown of this mechanism is 1:5, which, together with the vernier of our local factory (formerly produced), with a slowdown of 1:20, gives quite satisfactory overall slowdown, while the tuning density is obtained from 3.5 kHz per revolution (14 MHz) to 12 kHz per revolution (28 MHz).

Of course, I had to work with this node long enough to fit all the ranges, taking into account the selected division coefficients in the DPKD. The local oscillator frequency detuning scheme allows to provide a detuning from 8 to 25 kHz depending on the range, the elements of the DAFC system provide sufficient frequency stability even when QSO is made by digital modes (PSK31, MFSK16, etc.). - a divider with a variable division ratio (there were no registers in the "nightstand", therefore, on triggers), everything fit (without a +5 V stabilizer) on a 50x60 mm board; - DSB and CW driver in screen and tin plate..... on board 85x40 mm.

The balance is quite good if you pay extra attention to the selection of varicaps, the best option is when they are "almost" the same. A feature of the telegraph local oscillator is "soft" switching and the ability to control its operation from a computer through a well-known key scheme provided in any "help" of digital communication programs. The reference local oscillator is assembled separately on a 60x60 mm board.

The new version uses a bipolar transistor KT355A. The electronic telegraph key is assembled according to the well-known scheme published in the Radio magazine (slightly adapted to specific conditions) on a 100x20 mm mole rat, wired installation. The power amplifier is assembled on a 170x85 mm board.

The entire board is mounted on a radiator on the rear wall, and the transistors have good thermal contact directly with the radiator. High-frequency transformers of the pre-terminal and final stages are made in the form of "binoculars" from ferrite rings 600 NN K10x6x4 or the like.

The digital scale and the TsAPCh system are assembled on a 140x65 mm board; the scale is located vertically behind the front panel, the board has a cutout under the vernier in the form of an arch, above which there is a transceiver case from the TsSh-04 set (medium size) the proportions are very similar to the YAESU FT-747GX consists of front and rear frames, between which the chassis is located in the form of a "crib" with back panels.

On the rear panel there are connectors for power supply, RF signal, grounding, pedal, external PA control and electronic key manipulator.

Schematic diagrams of the transceiver

Author: S.N. Tarasov, Ulyanovsk, 73, de RW4LQ; Publication: N. Bolshakov, rf.atnn.ru

See other articles Section Civil radio communications.

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