HF PACKER
AMP
V4R6
Page 47
RF_IN). If not in transmit, the signal passes through the
normally closed contacts of K2 to K3. The also normally closed
contacts of K3 (when not in transmit) are routed directly to J4
which is connected to the SO239 connector on the rear panel.
So in receive mode, the BNC Connector is connected to the
SO239 connector. This is the bypass mode where you can
operate the transceiver with the AMP out of the circuit. When
K2 and K3 are closed (transmit mode), we divert the BNC
signal to the AMP input where it is amplified. Further
processing occurs in the LPF (low pass filter) which rejects the
harmonics of the AMP output. The signal from the LPF is
returned to J2 on the board where it passes through K3 to the
SO239 connector. The diode, D2, clamps the transient voltage
that occurs when current stops flowing in K2 and K3. Without
D2, you might see voltage spikes of 25 to 50V when the relay
is opened. It is best to prevent this transient noise from
happening.
TX Signal Generation
The TX signal comes from the collector of Q6. This transistor
output is either at 12V (receive) or 0V (transmit). Q6 is
controlled by U2 pin 5 through R21. TX cannot occur unless
the front panel switch is in the ON position. By placing the
switch in the ON position, you are enabling the AMP to
function. In the ON position you will have a ground signal on
pin 6 of U2. Otherwise this signal will be 5V as provided by the
pull-up resistor, R6.
PTT Control
We have discussed that the presence of RF through R4 can
trigger TX. There is an additional way to achieve TX. It is by
the Push-To-Talk input sensed on pin 3 of J4. This would be
an external contact closure to ground (12V common or case
ground). The contact closure is normally supplied by the
transceiver or SDR (software defined radio). A current flows
through an opto-isolation circuit in the 4N33 device, U3. The
output of U3 on pin 5 becomes an input to the controller, U2
on pin 3. An internal pull-up resistor in U2 keeps pin 5 at 5V
unless a valid PTT signal is detected. If detected, the pin 5
switches to 0V. With PTT control, you can hold the AMP in
transmit mode without having to have RF excitation on the
input. This is useful to reduce relay switching while pausing to
speak in SSB. The base of the transistor in the 4N33 has a 1M
resistor which reduces sensitivity and provides stable
operation.
CW or SSB option
CW or SSB is automatically selected. If you are using SSB,
the amp will optimize the hold time for SSB operation. For CW
operators, the default power up condition optimizes the hold
time for CW. As long as you are sending dots and dashes in a
normal CW manner, you will remain in the CW mode with the
hold time optimized for CW.
TEST Jumper, H3
A 2-pin header, H3 senses the users desire to test the AMP.
The TEST mode is useful for setting the bias current or
checking the DC-DC converter operation. You must have the
front panel switch in the BYPASS position for the TEST jumper
to function. If in bypass and the jumper installed, the PSU and
IPS signals will be at 0V while pin 5 of U2 will be +5V to
activate TX. Removing the jumper at H3 TEST will return PSU
and IPS signals to +5V and pin 5 of U2 will be 0V. The fan
output does not operate in the TEST mode.
Summary of Contents for PackerAmp V4
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