BLA350 PLUS
Solid State Compact HF 300W Linear Amplifier
User Manual
Revision 1.0 April 2019
3 Costruzioni Elettroniche srl
http://www.rmitaly.com
Introduction
The RM Italy BLA350 Plus is a fully automatic compact 300W HF linear Amplifier, that
builds on the success of the previous model. It now features a hardware protection circuit for
output impedance mismatch that is lightning fast ensuring the safety of the power transistors in
the event of high VSWR on the antenna connector. The RF deck has been improved as have
the output band filters. Frequency coverage is from 1.8MHz to 30MHz covering the following
bands, 160, 80, 40, 30, 20, 17, 15, 12 and 10m Amateur radio bands. It utilises two 50V
MACOM MRF 150 MOSFET Transistors in Push Pull configuration, (Class AB). It may be
used on all narrow band modes of transmission e.g. SSB,AM,FM, CW, RTTY, FT8 etc. It features a dual MCU controlled variable speed cooling system, a large analogue output power
meter and a 2 line 16 character LCD display that displays the amplifiers operating parameters,
such as frequency, filter selection, temperature and allows quick navigation of the amplifiers
menu system. Attention to correct operation and operating the amplifier within its operating
capabilities will ensure optimum performance and many years of trouble free use.
Specifications
Operating Frequency: 160,80,40,30,20,17,15,12,10m Amateur radio bands
60m band with reduced harmonic attenuation
No Tx <1.5MHz & >30MHz
Operating Modes: SSB,CW,AM,FM,RTTY,Data All narrow band modes
Input Power: 1-12W max
Output Power: 300W max
Harmonic Output: >-50dBc
Drain Voltage: 48Vdc
Drain Current: 15A max
Input Impedance: 50 unbalanced
Output Impedance: 50 unbalanced
RF Transistor: MACOM MRF150 Matched Pair
Amplifier configuration: Class AB Push-Pull
Cooling: Temperature regulated forced air cooling
Microprocessor: Microchip PIC 18F4620
Metering: Output Power, H/S Temperature, Band in use, Amplifier state
Protection: Input Power, Filter Error, VSWR, Temperature, Frequency
I/P—O/P Connections: UHF SO-239 (Low loss Teflon insulator), PTT input - RCA / Phono,
ALC output - RCA / Phono.
AC Power: 207-244Vac 3.5A max
Dimensions: 355 x 155 x 270mm (Width x Height x Depth)
Weight: 13.5kg
Supplied Accessories: AC Power cord
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NON RESONANT
ANTENNA TUNING WARNING!!!!
When using the BLA350 Plus amplifier together with a non resonant antenna and either a
manual or automatic antenna tuner it is very important the following precautions are taken.
The correct sequence for connection would be Transceiver, BLA350 Plus Amplifier, VSWR/
Power meter, ATU and Antenna
If using a transceiver with a built in ATU this function should be disabled if possible or operated in through mode as the input to the BLA350 amplifier is 50 Ohms. The internal ATU can
no longer tune the antenna.
Tuning of a non resonant antenna should always and only be performed at low power. Most
antenna tuners have a particular power rating and usually this maximum power rating is
quoted under tuned conditions. With the amplifier connected in line this should be done with
the amplifier either off or in stand by mode. Once an acceptable match has been provided
equal to 1.5:1 or better the amplifier may then be operated and the tuner may then be adjusted slightly to optimise the match. If this method is not followed and the antenna is tuned
with the amplifier running at full output the high impedances possible during the tuning process can cause damage to the amplifiers output transistors and should be avoided at all
costs. Failure to follow this procedure may well result in damage to the amplifier that is not
covered by the warranty
Quick Start Guide
1. Connect the RTX input connector (\) to the transceiver with a 50 ohm patch cable.
2. Connect the ANT output connector ([) of the BLA350 Plus to VSWR/Power meter and ATU if
required or directly to the antenna if resonant at the operating frequency desired.
3. Connect the PTT output cable from the transceiver to the PTT input (_) of the BLA350 plus.
(BLA350 Plus PTT input is Active Low).
4. Make sure the ON / OFF switch (a) is set to OFF, Switch (_) MAN (Manual) / AUT (Automatic)
is set to ‘AUT’ and that switch (\) Stby (Standby) / AUT (Automatic) is set to Stby.
5. Connect the AC power cord to the amplifier (`) and household AC outlet .
6. Make sure that the amplifier is OFF (a) or in Standby mode (\).
7. Adjust the transceivers output to 10W, if capable of more than 10W output.
8. Test that the antenna connected is correct or tuned for the current frequency selected. If necessary
match the antenna to the desired frequency with the ATU. This must be done with the amplifier
switched off or in standby mode.
9. Switch the Stby / ON switch (\) to ON.
10. Now when the PTT on the transceiver is pressed the amplifier will switch to TX, indicated by the
front panel LED (d) and an indication of the output power (b).
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