Technical data:
Fq
1296.800 MHz
Est freq drift < 26 Hz per year
Pout
42.4 dBm (17.4 W) into cable (measured 2000-09-13)
Keying A1A
( 3x "SK6MHI" + 1x "SK6MHI JO57TQ"... carrier on for approx 45 s)
Key up/down > 80 dB
Antenna Alford
slot, approx 7 dBi +/- 2 dB (360 deg)
Cable loss approx 2dB
Estimated EiRP 47 dBm +/-2 dB (50 W +/-2 dB)
FREQUENCY ACCURACY
Beacon frequency is locked to a 5 MHz OCVCXO. Specification for
the oven is +/- 2E-8 overall frequency stability over 1 year. This gives
that the beacon frequency should not drift more than 26 Hz per year. Frequency
has been adjusted to nominal 1296800000 Hz by a rubidium locked frequency
counter in July 1999.
Technical description
VCXO
The VCXO is an emitter harmonic
oscillator with a capacitance diode from the xtal to ground. A PMB2306T
from Infineon (Siemens)is used in the PLL-circuit. The PLL dividers are
loaded from a PIC (16C84) at power on which then (the PIC) goes into beacon
mode and generates the keying of the beacon. The buffer amp in the VCXO
box is driven into compression and generates harmonics, the fourth harmonic
is filtered by a helixfilter (432.266 MHz).
x3 MULTIPLIER AND DRIVER AMPLIFIER
The 430 MHz signal is fed into the next amplifier MSA-2111 which
is also driven into compression and the third harmonic is filtered out
by the 1296 MHz helixfilter. The 1296 MHz signal is amplified and filtered,
output power from this box is approx 30 dBm. Keying is accomplished by
keying the voltage feeding the MMIC amplifiers. The last stage in this
box is a LDMOS amplifier using a ERICSSON PTF10107 GOLDMOS (5 W device)
that gives 15 dB of gain.
POWER AMPLIFIER
The PA consists of two ERICSSON GOLDMOS PTF10053 (12 W device)
and wireline hybrids. Matching networks are simple 50 ohms microstrip lines
with capacitors to ground. The two LDMOS stages are feed with 27 V from
independent voltage regulators. In case of failure in one of the FET:s
the other one can still operate and the beacon will lose 3 to 6 dB of output
power. The driver amplifier gets its voltage (26 V) from those two separate
voltage regulators via diodes.
PSU
The power supply is a simpel ordinary design. It uses PTC resistors
on the secondary side as fuses. There are four separate voltage regulators
8V, 12V and two for 27 V. The 27V regulators supply each side of the PA.
ANTENNA
The beacon antenna is an ALFORD
SLOT which approximately have 7 dBi of gain.
Inside SK6MHI
Changed 2000-09-20 by SM6PGP