Front and Rear Panel Description
1.
Displays currently selected filter (Auto and manual modes)
2.
Manual / Auto filter selector
3.
Output power meter
4.
Protection warning LED
5.
ON LED
6.
3dB Attenuator ‘on’ when attenuator inserted (manual or automatic)
7.
TX LED illuminates when amplifier is in transmission
8.
Amplifier ON / OFF Switch
9.
3dB Attenuator ON / OFF manual switch
10. SSB Delay switch
11. RF Output SO239 Socket to Antenna (ANT)
12. RF Input SO239 socket to Transceiver (RTX)
13. PTT input (Phono / RCA) (Active Low)
14. DC Power Supply cable (Red Positive / Black Negative)
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 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. The ANT output of the amplifier should then be connected to an-
tenna being used. (Usually there will be a SWR / Power meter immediately after the output on
the amplifier followed by an antenna tuner if a non resonant antenna is being used. This order
of connection is very important. (if the drive radio has a built in antenna tuner this should be set
to OFF / Bypass or Through mode as it can no longer be used to tune the antenna as it is only
looking at the input circuit of the amplifier. If a non resonant antenna is being used then an ex-
ternal ATU is required connected on the output of the amplifier before the antenna. Check also
that both the ATU and Antenna are suitably rated for the power output levels. (Antenna SWR
should not change much from low to high power) (ATU’s usually have a power rating and most
often this is the power handling under tuned conditions
NOT
to be confused with the power
handling whilst being tuned. All antenna tuning should be completed at low power with the
amplifier switched OFF! Not only does this allow for the drive radio, amplifier, ATU to not be
damaged but it also causes less QRM on the bands)
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. Immediately after switch on the
PTT input socket is disabled, (Additional protection), The first transmission made using the
internal RF sense circuit will then activate it. In normal use this does not affect operation and is
completely transparent, however trying to trigger the PTT with no RF, immediately after switch
on is not possible. (For instance testing the radios PTT O/P)
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 multiway connectors on the rear
panel. See the radios operating manual for further details. SSB delay on the front panel should
be set to OFF as the PTT output from the radio will control this.
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 12V to 16V DC without damage. The current rating of the power sup-
ply must be at least 30A continuous but 45 to 40A 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.
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.
