HF PackerAmp V4, Руководство по монтажу

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transformer T1, where the two signals are recombined in
phase to produce a single output. T1 also provides impedance
transformation from the low output impedance of the
MOSFETs to the 50Ω antenna port. DC power is provided to
the drains of Q1 and Q2 by phase-reversal choke, T2. This is
a very effective method to provide power to Q1 and Q2 while
presenting a high impedance to the RF signal over a broad
range of frequencies. The drain chokes for Q1 and Q2 are
wound on the same core, and the phase of one of the chokes
is reversed. C5 increases the bandwidth of impedance
transformation provided by T1, especially at 21 MHz. The 5 V
bias supply voltage is derived from a 78L05 regulator. Bypass
capacitors C4, C6, C8 and C1 remove RF voltages from the
bias supply voltage. Gate bias for Q1 and Q2 is controlled
independently. VR1 adjusts Q1's gate-bias voltage via R1 and
L1. VR2 works similarly for Q2 via R2 and L3. At low
frequencies, the amplifier's input impedance is essentially
equal to the series value of R1 and R2. L1 and L3 improve the
input-impedance match at higher frequencies. The low value
of series resistance provided by R1 and R2 also reduces the
Q. A Resistive Pi Network comprised of R3, R7 and R8
provide a 50 ohm impedance to the transceiver and to the
AMP. The standard network attenuates the RF Input by 9dB
which is a 8:1 power ratio. The maximum RF input of 5W is
reduced to 0.63W to the gates of the MOSFETs. The
attenuation matches the popular FT817 power setting of 5W.
The maximum of 0.63W is below the distortion level of the
MOSFETs. This is important for distortion free SSB operation.
The bias current is 100mA per MOSFET while transmitting. The switch-mode p ower supply circuits boost the
nominal 12 VDC input to 29 VDC at 3-4 amperes during voice
peaks. The power supply is normally off unless commanded to
be on by the Controller IC, U2. During receive or standby
current is very low. There is an approximate 26 mA current
draw when power supply is off, and 95 mA current draw when
power supply is on and 3-10A current draw when the amplifier
is keyed by a transceiver.
Performance
The chart shows the typical gain vs frequency you can
expect from the HF Packer-Amp. The average power out is
approximately 35W. The fall off in performance at 30MHz is
due to the MOSFET characteristics. This chart was made with
a constant RF drive input.
The Controller , U2 is a Microchip PIC16F688 device.
RF input at J3 is tapped by U6, RFM2 Module to provide a
signal to the controller for Carrier Operated Sensing. This
signal causes the controller to sequence the PSU signal, the
IPS signal and TX signal for correct operation. The PTT input
may also be used to activate the amp independent of RF
sensing. The TX signal (Q6) operates the T/R relays K2 and
K3 to switch from the RX state to the TX state. The controller
is asleep during receive mode to inhibit controller noise..
Terms used in the descriptions
•
PSU – Power Supply Unit
•
IPS – Intelligent Power Switch
•
PTT – Push To Talk
•
AMP – Amplifier