Beacon
Configuration
Beacon contain five parts: power suply, temperature control unit, identifying keyer,
transmitter and antenna.
Power suply
Network voltage is transformed to value 15 V. After 4-way rectifier folow integrated
stabilizator MA 7812. Three DC voltage are on the output of power suply: 15 V
nonstabilized for heating of temperature control unit, 12 V stabilized for transmitter
and for control circuits of temperature control unit and 5 V (voltage is eliminated from
12 V over the resistor) for identifying keyer. Whole power suply is fused on primary
and secondary side.
Temperature control unit
Heating part and transmitter are in the one block. This one is located in metal
box, which is heat isolated. Temperature sensor is termistor and heating
body is power transistor. Electronic part contain integrated circuit MAA 723.
Control unit working in proportional mode. Power input of heating is 6 W.
Temperature is maintain on 50 degrees Celsius inside.
Identifying keyer
Whole keyer contain folowed integrated circuits series TTL: MH 74154, MH 74150, two
pieces of MH 7493 and timer NE 555. Identification is "stored" in diode
matrix, which has 16 multiple 16 swiched points. NE 555 generate stroke
frequency and that going to two counters MH 7493. These counters control circuits
MH 74154 and MH 74150 (multiplexer and demultiplexer) - they read diode
matrix. Speed of transmitting text is depend of frequency stroke generator.
Text of beacon is: "OK0EN BEACON QRP" and after this folow dash 8.5 second
long. Whole text, including dash, is repeating every 29 seconds.
It represent speed 50 characters per minute.
Transmitter
It is modificated circuit by OK1CZ. Oscilator is on transistor KC 508. In series
with crystal 3600 kHz is connected varicap for fine tuning frequency of
transmitter (about +/- 150 Hz). After oscilator folow power amplifier (KFY 34)
and from its output go carrier over the double PI cell and serial inductor
to the antenna. Keying is done in the collector of PA tranzistor by other transistor KF 517.
Keying pulses are not going to its gate directly, but by small relais,
because of right form of CW signals without sharp edges. Power input of PA is 300 mW.
When we will supposed efficiency 50 %, it is possible to say that power output
is 150 mW.
Antenna
Antenna is a half wave dipol. Shoulders contain angle 100 degrees and are little
bit inverted - about 5 degrees. Direction of maximum gain is oriented to east - west.
Beacon is located in loft of private house. One of shoulders of antenna is in loft
(because piece of land is not large) and second is cathed between top of the roof
and the ground. Antenna is only 8 metres above the ground with the good conductivity
(large pond is near).
General configuration
Transmitter and heating part of temperature control unit with heat isolation is composed in the
one mechanical block. Other parts of beacon (without power suply), are installed in the next
plastic box. This one is connected to the transmitter with cable. Both two parts
are located in the big heat isolation box (second isolation). Power suply is separated
in the metal box, out of beacon. Whole equipment is protected against fire. Power input of
whole beacon from network 220 V is 10 VA.
Thanks
Thanks to OK1CZ, OK1MC (silent key),
OK1DGI, OK1FAQ, OK1FIP,
OK1FVD and OK2PXJ for advises and help with construct of beacon.
For publicity of beacon in OK and foreign countries thanks to OK1HH,
OK1RR, OK1CRA, OK1FVD, OK1FWA, OK2PXJ, DJ5QK, DL1AAA and G8PG.