Shelezyak's Planet - circuit diagram of an FM tuner with computer software control.

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                            FM-ТЮНЕР
  (c) В.Казаков             ~~~~~~~~

  Как и обещал в прошлом выпуске, предлагаю вашему вниманию схе-
му FM tuner with software control for a computer Spectrum.
The tuner circuit consists of an analog and digital part.

 Analog part

  The VHF receiver circuit was taken as the basis for the analog part of the circuit.
ka from #6 of the magazine "Radio" for 2000, which is
almost typical circuit diagram for switching on a microcircuitK17CHKHAZCH
(TDA7021). To make a printed circuit board for the device, you can use
use the board drawing from the same issue of the magazine, adding
wiring of the digital part of the device to it and discarding the unused
elements included in the FM-TUNER circuit.
  The analog part of the circuit must be shielded, especially if
A switching source is used to power the computer.  If
interference is not eliminated even after shielding, then we can recommend
Use a five-volt battery to power the tuner,
removing elementsR6 and VD1 from the tuner circuit.
Signals "Out A" and "Out B" are supplied toaudio amplifier -
on a computer or on active speakers. To increase the volume
For this output signal, you can add an amplifier using one transistor
tore (as in Radio #6 2000) between resistorR5 and resistors R8
and R9.
 ┌──o───o───o──o───────o──── ──o─────────o──o───███─<+12V
 │ │ │ │ │ ─┴─ ─┴─ + +5V │ │ R6
        │ │ │ │ │ C5 ─┬─ ─┬─ C6 │ │
        │ │ │ │ │ ─┴─ ─┴─ │ └─┤<├───┤
        █ │ │ │ █ ┌─────┐ C12 │ VD1
      R1█C2│ C3│ C4│ █R3 ├─██─┤9 8├───┐ o──────────┐
        █ ─┴─ ─┴─ ─┴─ █ R4 │ │ ─┴─ │ VD2 │
        │ ─┬─ ─┬─ ─┬─ │ ┌──────┤10 │ ─┬─C13│ ┌┤>├├─o──o
        o──┘ │ └──o ─┴─ │ 7├───o─┤├─o │ │ │
Kan- │ │ +4.5V│ ─┬─ C7 │ │ C14│ │ C19─┴─ )L4
tenne o────┐ │ │ └──────┤11 6├─────┤├─o │ ─┬─ )
>────┤├─┼──┐ │ │ │C8 │ │ │ │ │ )
  C1 ┌─o ) ( │ │ ┌──────┤12 5├────────┼─o─────o──┘
      │ │ ) ( │ │ ─┴─ C9 │ │ C15 │ │
    R2│ █ ) ( │ e│ ─┬─┌─┤├─┤13 4├───o────o ─┴─ C20
      ┴─█ ) ( │ b │/ │ │ │ │ ─┴─ │─┬─
        █ │ └─o────┤ │ │ ┌──┤14 │ ─┬─ │ │
        │L1│ L2 VT1│ to │ │ │ │ 3├───o │ █ R7
        │ │ o──┘ │ o┤├┤15 │ ─┴─C16│ ─┬─ █
        o──┘ ) C10│ │ │ 2├─────┤├─o │ └──R1 3.3 k C1 4..15(substring) C11 0.1 mk VD1 KS156
R2 15 k C2 0.02 mk C12 330 VD2 KV109
R3 150 C3 4..15(adjustment) C13 1500 DA1 K17CHHAZCH
R4 10 k C4 0.01 mk C14 0.1 mk VT1 KTZ102
R5 47 k C5 0.068 mk C15 0.068 mk
R6 680 C6 220 mk x 10V C16 0.1 mk
R7 68 k C7 3300 C17 0.1 mk
R8 2.7 k C8 10 C18 1 mk x 10 V
R9 2.7 k C9 1500 C19 22
             C10 100 C20 3300

L1 - 3.5 turns of PEV-2 wire with a diameter of 0.3 mm, L2 - 2.5 turns
PEV-2 wires with a diameter of 0.1 mm. Both are wound on the same frame
5 mm in diameter, ordinary winding.
L3 - 20 turns of PEV-2 wire with a diameter of 0.5 mm on a mandrel of diameter
rum 2 mm.
L4 - 7 turns of PEV-2 wire with diameter0.8 mm on mandrel diameter
rum 6 mm.
 Digital part

  The digital part is a diagram of port #FB (251) -
Pentagon printer port (without using signals  BUSY  and
STROBE) - with a DAC connected to it, made on the basis of re-
positive R-2R matrix.  This diagram was taken from the magazine
ZX Format.
  Using resistor R3 you can adjust the output value
DAC voltage.
DD2
 3 ┌───┬──────┬──┐ 2 R1 R3 ├──┐
             D0────┤D0 │ RG │ 0├────███────о─────о───███─о─>
                 4 │ │ │ │ 5 R1 █R2 │ Analog channel
             D1────┤D1 │ │ 1├────███────o ─┴─ goy
                 7 │ │ │ │ 6 R1 █R2 ─┬─C1 parts
             D2────┤D2 │ │ 2├────███────about │ tuner
                 8 │ │ │ │ 9 R1 █R2 ─┴─
             D3────┤D3 │ │ 3├────███────o
                 13│ │ │ │12 R1 █R2
             D4────┤D4 │ │ 4├────███────o
                 14│ │ │ │15 R1 █R2
             D5────┤D5 │ │5├────███────o
                 17│ │ │ │16 R1 █R2
             D6────┤D6 │ │ 6├────███────o
         DD1 18│ │ │ │19 R1 █R2
        ┌──┐ D7────┤D7 │ │ 7├────███────o
/IORQ 3─┤ 1│6 11├───┤ │ │ █R1
A2 4─┤ о───────┤>C │ │ │ │
/WR 5─┤ │ 1 ├───┤ │ │ ─┴─
        └──┘ ┌────o0E │ │ │
             ─┴─ └───┴──────┴──┘

DD1 K555LECH R1 15 k C1 6800
DD2 KSSUP23 R2 7.5 k
                 R3 10k
 Settings

  To configure the tuner, you can use the program
"FM_TUNER", which is given in the appendix to the newspaper.
  After applying power to the tuner and loading the program "FM_TUNER"
resistorR2set the voltage drop to R3,equal
0.5 V. Then it is necessary to lay the boundaries of the selected
th range by shifting and spreading the coil turns
L4. In addition, you can change the range boundaries using the
resistor R3 in the digital part of the tuner.  Tuning into the station
resistorR5 set the required sound volume level.
And, in conclusion, with the help of capacitorsC1 and C3they achieve maximum
Maximum sensitivity when receiving weak signals.

Software

  Can be used again as software
the same program "FM_TUNER". This program is currently available
Allows you to perform coarse and fine tuning to a station, as well as
Exit the program in TR-DOS and load boot.  In bu-
in the future, when using signals BUSYandSTROBE and accordingly
further refinement of the scheme (introduction of the second VHF sub-band, sub-
turning on a stereo decoder, etc.) an introduction to the software is possible
provision of other service functions, such as enabling/disabling
Changing tuner power, switching subbands, auto-tuning
to station, automatic selection of stations, automatic switching on
Enable/disable STEREO mode independing on the signal level,
setting indicator, etc.

MODULATORS
 ~~~~~~~~~~
 (c) Kruzo/56 / I. Zhovtonoga

 The presence of a high-frequency modulator on the computer allows
will connect to a television receiver that does not have a video input.
The exception is the situation when the modulator operates in
range of decimeter waves, and the TV does not have a corresponding
general selector.
  It is very convenient to use a ready-made modulator from a video console
"SEGA". The circuit of such a modulator is shown in Fig. 1.It has
audio and video inputs.  It operates around the frequency of the 10th channel -
la. If you open the box in which it is located, you can see
put four multi-colored wires going to the modulator board. Their
purpose in order of connection to the board starting from the one closest to
board corner:

 brown - general
 white - +5 V
         yellow - video input
         red - audio input

 It is quite possible that modulators with a different
design.  Then you can navigate by connection
conductors to the plug contacts shown in Fig. 2. 
 In radio products you can find modulators that are used
in VCRs.    They were built using
specialized microcircuits.   Schematic diagrams of two
modulators on microcircuits LA7054  and TA7673P  are in l.1.
Modulator on a chip TA7673Poperates in the meter range
waves, but usually such modulators operate in the decimeter
range.
  The modulators have the same dimensions and differ in the number
switches.
  The appearance of the modulator of one of the possible options is shown
in Fig. 3. The numbering of contacts is arbitrary.
 The common or body pin in modulators of other options can
connect not to the 1st, but to the 5th contact.  Then 1st contact
may not be.
  Switch S1 shown in ON position
TEST generator, but there may be a modulator with reverse
position S1.
  Modulator designs for self-production are available
in l.2-l.7.Literature:

 1. Consumer electronics. NEAL "RL". Radio amateur #1/91 p.4-5
 2. PAL-SEKAM transcoder.  Transcoder transmitter. I. Mostitsky.
    Radio amateur #1/93 pp. 2-3
  3.HF generator for PC. M. Shustov. Radio amateur #2/93
  4. Video signal transmitter to a television receiver.
    E. Bobonic, P. Bobonic. Radio amateur #9/94 page 5
  5. Radio frequency generator for BKOO10.   A. Kuzmenko.
    Radio amateur #9/94 page 11
  6.Modulator. N. Martynyuk. Radio amateur #9/97
  7.Forward bias sensors in controlled generators.
    M. Shustov. Radio amateur #10/97 pp. 17-18
  8. Features of the circuitry of 16-bit video consoles. S. Ryumik.
    Ukraine. Radio #4/98 pp. 29-32

V.K. Figures 1, 2 and 3 are shown in the appendix to the newspaper.

 AMENDMENT
 ~~~~~~~~
 (c) Kruzo/56 / I. Zhovtonoga

  In the 50th issue of the newspaper  "CITY"  in the article about cache, the author was
The chip was named1SSLA2,and it was necessary - 1SSЛЛ2.