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As soon as power is applied to the tuner PCB, the microcontroller begins sending out a command byte to
the 2050 through connector P1. This is to inform the 2050 that it is connected in the Manpack configuration
and to setup for portable operation. When the 2050 receives this command byte it replies with an
acknowledgement byte and the tuner goes into standby mode waiting for command data from the 2050.
Tuning Algorithm
The 2050 Transceiver initiates a tuning sequence by sending out a command byte to the microcontroller.
At the same time the 2050 provides a RF signal which the tuner uses to find the best result. By default the
tuner assumes that the whip looks capacitive. Firstly it will find a starting inductor, determined by whichever
inductor makes the whip look slightly inductive, and then initiate a binary search algorithm. Once this is
completed the impedance transformer will attempt to match the whip to the transmitter by switching its
three impedance ratios and optimising the RF feed current. If this current is not high enough the binary
search algorithm is reinitiated with series capacitor C15 switched in. This takes care of the whip above
resonance where the inductance is small. The impedance transformer will try to match the whip to the
transmitter to give highest feed current.
If the feed current is not high enough the tuner assumes that a long wire antenna is connected. Generally
use of the long wire will involve tuning out much larger inductances so shunt capacitors C21 and C22 are
employed to make the wire appear slightly capacitive. Since the required reactance to tune out this
residual capacitance will be small, a sequential tuning algorithm is employed using only the smaller tuning
inductors. The combination which produces the highest feed current is assumed to be the optimum. Finally
the impedance transformer will attempt to match the resistive component of the long wire to the transmitter.
Once the tuning cycle has been completed the tuner will output a command byte to the 2050. This
command byte tells the 2050 if a successful tune was achieved, or if no tuning result could be obtained.
The tuning time will vary from two to four seconds depending on the transmit frequency and whether a
whip or long wire is being used.
Specifications
DC current requirement
Static
-
Less than 20mA
Tuning
-
500mA
(Max).
Supply voltage
10 VDC - 15VDC
Maximum input power
Max
30W
Operating frequency
2.5 MHz – 30 MHz (8ft whip)
2.0 MHz – 30 MHz (Long wire)
Tuning time
1s - 4s.
Maximum output Voltage
< 2kV.
