BLA350 PLUS Solid State Compact HF 300W Linear Amplifier User Manual Revision 1.0 April 2019 3 Costruzioni Elettroniche srl http://www.rmitaly.
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.
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.
Front / Rear Panel Description Front Panel 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. LCD Display - displays amplifiers operating parameters and menu system Standby / On - In standby the amplifier does not amplify the incoming signal.
INSTALLATION Carefully remove the amplifier from it’s shipping carton and inspect for any damage. The amplifier should be installed in a place that allows good ventilation and provides a suitable base to support it. Failure to allow for good ventilation will cause the amplifier to overheat and shut down prematurely. Air is drawn into the amplifier from both the underside and top cover of the amplifier so do not place any objects underneath or on top of the amplifier that may restrict these intakes.
depends on how the equipment is connected and the type of antenna used. There are both arguments both for and against the stereotypical RF station ground. In addition to this is that lightning and static protection for the antenna is an additional subject in itself, however this should be kept external to the building and will not be covered here. There are many good articles about correct station grounding both online and in all of the usual publications on Ham Radio from the ARRL and RSGB etc.
Operation CW Operation The BLA350 Plus utilises conventional relays for RX / TX switching and so due to the finite switching time, (20ms), ‘CW Full Break-In’ may not be used. It is recommended that the PTT cable from the transceiver is connected to the amplifier and that the ‘CW delay’ on the transceiver is adjusted accordingly so that when the key is pressed there is a predetermined delay to allow the BLA350 Plus RTX relay to switch from RX to TX before RF appears on the input.
ALC ME NU A L C Int., (Internal), VOX when enabled allows the BLA350 Plus to be used if the transceiver does not have a PTT output. There are two Options ‘Disabled’ and ‘Enabled’. The BLA350 Plus default setting is ‘Disabled’ from the factory. It is recommended that for CW and SSB that the external PTT input is utilised. If Int. VOX is enabled see also menu SSB Delay below.
Analogue Power Meter (b) Displays the output power in Watts RMS. Dimmer ME NU D i mm e r Front Panel LED’s ON (c) Illuminates GREEN in Operate mode indicating that the amplifier is ready to use. Adjust the brightness of the LCD back light between two levels, High and Low. Default Setting is High. Info TX (d) Illuminates RED when the amplifier is in Transmission. Selecting this menu displays the current version of the firmware.
Protection Excessive VSWR The BLA350 Plus measures both the forward and reflected power at the antenna output and also at the input to the low pass filters. The antenna VSWR protection features a lightning fast hardware protection circuit. However both protection circuits are also monitored by the microprocessor. The amplifier will protect itself if the wrong band filter is selected or if the antenna VSWR is excessively high.
The figures below show the typical performance of the the BLA350 Plus amplifier. However due to component tolerances and AC supply voltage each amplifier will show some small variation compared to the data shown below.
Warning: Transmit Time. High duty cycle modes such as FM and data modes, (RTTY / FT8 etc.), operate the amplifier at full power all of the time, unlike modes like SSB and CW that are either intermittent or only reach peak output for very short times. These high duty cycle modes will run the amplifier much harder and generate more heat in the same amount of time. It should be noted that the amplifier although capable of being used with these modes, should not be used continuously.
