Installation:
Unpack the amplifier from it’s shipping carton and inspect for any signs of damage. The ampli-
fier should be installed (either fixed or mobile installation), in a place that allows good ventila-
tion and provides a suitable base to support it. Failure to allow for reasonable ventilation will
cause the amplifier to overheat and shutdown prematurely. A short 50 Ohm patch lead should
be used to connect the amplifiers RTX SO239 input connector to the output, (Antenna Socket)
of the drive Radio. This length of this cable is not critical but should be of good quality and be
kept as short as practically possible and suitable for VHF operation. The ANT output of the
amplifier should then be connected to antenna being used. (If an external SWR/Power meter is
to be used the amplifier should be connected to the input and then the antenna to the output,
however this is not required as the amplifier has a built in power meter and SWR indication).
This order of connection is very important. Check also that the Antenna is suitably rated for the
power output level. (Antenna SWR should not change much from low to high power). The
antenna should be tuned before connecting the power amplifier or with the amplifier switched
OFF! However as most VHF antennas require initial tuning after installation this should not be
an issue.
The amplifier also has a PTT input located on the rear panel. This may or may not be con-
nected. If left unconnected the amplifier will still function as it contains a RF sense (similar to
VOX), circuit that will automatically switch the amplifier to TX when it detects RF on the in-
put. The PTT input is configured as active low which means that shorting it’s terminal to
ground will trigger the amplifier to enter transmit. (This is the way nearly all modern trans-
ceiver PTT outputs are configured either open collector or relay and may be connected directly
to the PTT input on the amplifier with a suitable cable. The PTT input socket requires a Phono
or RCA type plug and should be made with a screened cable.
If the PTT is connected to the radio it must be connected to the PTT output on the radio. On
modern transceivers this is usually embedded in one of the multi-way connectors on the rear
panel, and may also be band specific. See the radios operating manual for further details. SSB
delay on the front panel should be set to AM/FM for all modes as the PTT output from the radio
will control the switching.
In SSB mode If not using the PTT input the front panel switch
]
should be set to SSB. This
adds a short delay to the release time of the RTX relays so that pauses in speech do not cause
the relays to drop out. The PTT input is however recommended for SSB operation, in which
case the switch should be set to AM/FM mode.
The amplifier must be connected to a suitable power supply of the correct voltage output and
sufficient current rating. The output should be 13.6 or 13.8V DC but the amplifier may be con-
nected to a supply from 13V to 16V DC without damage. The current rating of the power sup-
ply must be at least 40A continuous but 45 to 50A rating is advised. Be aware that the current
rating must be greater still if the drive radio is also connected to the same power supply, al-
though this is not generally advised.
The voltage output and current rating are very important for low voltage (12V) RF transistors as
voltage sag, (poor load regulation) or insufficient current capability can drastically reduce the
output power or cause distortion.
