Radio station at 144 MHz, or How to make something out of nothing .... Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Civil radio communications

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This construction is not for repetition, but rather a description of how to make something out of nothing. Of course there will be diagrams. But since a lot of really improvised materials were used, I'm afraid it will not be possible to repeat this completely. They put what is available and at hand. This article can be hung even on fences, but do not assign authorship!

Part one

Is it possible to make a station at home that is not inferior to the bourgeois one? (meaning 144 MHz) Yes and no. In terms of characteristics, the Mayak is capable of surpassing the bourgeois consumer goods. In terms of sensitivity, it is not inferior, in selectivity it wins, in terms of appearance and control interface, of course, "Mayak" is completely out, in terms of the operating range of 130 - 174 for "Alinco DJ-191", 2 MHz overlap for "Mayak", but we do not going to work outside the allowed range :). Compare for yourself: Mayak has a spiral resonator at the input, most bourgeois stations have a preselector on 2-3 circuits, which are pulled by varicaps. The output power is at the same level: automobile bourgeois pump 50 - 40 watts from a $60 microassembly, RW9UGA (Alexander, Anzhero-Sudzhensk) from the Mayakovsky terminal for 300 rubles received about 50 watts.

I was given a technical task (from RA9UNY, Yaya, Mikhail) to make a station for a "two" in minimum dimensions with maximum bells and whistles at an affordable price (although RA9UWD, Yaya, Igor, said that "It won't work anyway", I told him did not believe):

Naturally, I started with a synthesizer. Synthesizer should be simple, without multipliers. XK3 was immediately discarded due to the use of PC10 - these are two buildings. Of the available and not very expensive were: 1015PL2 and 1015PL5, surface-mounted cases (hereinafter referred to as SMD), PL5 with parallel input of division coefficients (therefore, a processor is not needed, you can get by with a diode decoder), PL2 with serial input - you can’t do without a processor. Bourgeois single-chip synthesizers were not considered due to the lack of descriptions (and in vain, but then another $10 would have to be spent).

Processor (microcontroller) must have a non-volatile memory (EEPROM) for storing frequently changed parameters (eg grid parameters, memory channels), and a rewritable program memory (FLASH) and programming by wire pair. We use an AVR processor from Atmel. About PIC from Microchip, I could not get enough information, although it is also a powerful thing. 8048 and others like it (8051) was immediately dismissed due to the large dimensions and the use of an external ROM (3 cases at least) (see "Mayak River Station Control Board", "Radio" 2000, (c) RA9UCN, Vladimir, Mariinsk) In the future, a more expensive AVR will be used (it has 8 kb FLASH, 4 ports x 8 lines, $ 10), and now a cheap AT90S1200 (1 kb, $ 4) is used for debugging.

Indication. You can install an LCD - it's cool, but expensive ($10 is money for me). It was decided to put an LED indicator from the Chinese radio. We will display the last 3 digits, and 144 or 145 will display "`" in the leftmost digit (the Chinese saved and in the 4-digit indicator the leftmost digit instead of "8" made "1"). We will output the information sequentially using 561IR2, and after the output of the information and the number of divisions in the ms of the synthesizer, the processor will fall asleep so that it does not make noise.
The noise from the synthesizer and the processor is a separate conversation. Control unit in the river. Station "Signal" is noisy at 6 - 7 points.

Output cascade - KT610 or so, with a 12-volt supply, it swings directly from the VCO. VCO - from "Mayak".

Application - with one conversion, 1 IF - 10,7 MHz, IF is detected by 174XA6, it has built-in noise reduction, S-meter.

When prototyping the synthesizer, SMD resistors and blocking capacitances were used, the remaining capacitances (LPF, etc.) were used by CD, CT. Data for 1015PL2 was taken from the computer's LPT port and output by a simple assembler program. 1015PL2 was taken in a typical inclusion. With a 10 MHz quartz resonator, 5 kHz and 25 kHz grids were used for testing.

Prototyping Revealed

• The acceptability of the option when the p-station synthesizer is controlled by a computer (well, if you do not take into account the noise from the computer). Any illiterate high school student is capable of writing a program that shoves data into the port and occasionally, reading something from there.
• A very strong influence of pickups on the wires through which the data goes in PL2. They are eliminated by three blocking capacitances on the PL2 terminals.
• A not entirely clear breakdown of the PLL when modulation is applied to the input of the VCO. Apparently, the LPF is buggy. Will be eliminated.

Frequency meter for VCO output, oscilloscope for LPF output. It is not necessary to use devices, it is enough to step by step tracing the program with LEDs to make sure that the necessary data goes to the input of PL2, and the same data appears at the control output at the next boot. Set the center frequency (145`000), voltmeter to the VCO control input, turn the VCO coil to set half the VCO supply (if the PLL captures, the LED will turn off).

At the moment, all nodes are mocked up, the layout of the nodes is being developed, the program is being written and the interface is being developed. The interface will probably be like RA9UCN. Since there is not enough memory, the program will be crooked.

So

Bourgeois cheap stuff can now be purchased for $ 100 and not soar your brains. But if the brains have nothing to do, then a decent station can be assembled from practically improvised materials. Then, showing permission to work on the air, you will not blush and hide the potbelly stove, but proudly show a mountain of guts with light bulbs.

Author: Sergey Gimaev, RW9UAO; Publication: N. Bolshakov, rf.atnn.ru

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