| febrero 20, 2020

Solid State Compact HF 300W Linear Amplifier

BLA350 PLUS - RM Italy


FCC 47 CFR 97.307, 97.317

Equipment Under Test (EUT)

Trade name: BLA 350 Plus
Serial number: 021019
Firmware revision: 1.15F
Hardware revision: Rel 1.15
Application: Amplifier
Power supply: 230 / 60 Hz AC
Highest internally generated
or used frequency:
16 MHz
Amateur Radio bands as defined in
Manual BLA 350 Plus:
160 m, 80 m, 40 m, 30 m, 20 m, 17 m, 15 m, 12 m, 10 m
60 m band with reduced harmonic attenuation
No Tx <1.5 MHz & > 30 MHz
Output power: 300 W
Ports: ANT
PTT InIEC (European AC input socket)(see Annex 3 for detailed information)
Accessories delivered with EUT: Exciter, Signal Generator, cable harness (see chapter 2.3)
Variants: None
Remarks: None

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.


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 Ohm. unbalanced

Output Impedance:    50 Ohm. 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


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

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. We recommend that the transmission time should not exceed a couple of minutes in order to avoid excessive transistor junction temperature. The exact time for transmission in these modes will of course depend on numerous factors such as, the ambient temperature, how good the ventilation surrounding the amplifier is, if there is sufficient space for freely flowing air to circulate etc. If the ambient temperature is high this will reduce the total time in transmission.

Common sense should be exercised if the heat sink temperature is high then sufficient time should be allowed for it to cool down before resuming transmission. For high duty cycle modes the amplifier may also be used at less than maximum output power by reducing the input drive level. This will reduce dissipation and also allow the amplifier to be used for longer periods.

Input Drive and Power output.

The BLA350 Plus should give full output power with approximately 10-12W of drive. Excessive input power should be avoided and the amplifier always used in a responsible manner. If excessive input power is used the amplifier will signal an error and above 15W input it will return an alarm signal and block transmission. It is important to understand that accidental input of 100W from the transceiver should be avoided and may cause damage to the amplifier!!!!

Maximum Output Power Considerations.

All amplifiers have a maximum output and this occurs shortly after gain compression where by Pin no longer produces a proportionate increase in power output. The amplifier should always be operated at a point below its saturated output. Trying to extract every last watt by overdriving the amplifier will NOT actually help your signal be stronger, you will in fact cause higher levels of distortion which will make your signal less intelligible at the distant receiver station.

Running the amplifier a little under maximum output power will allow the amplifier to run cooler and make it more reliable for many years of use.

As an example consider the following situation.

1 ‘S’ point on a receiver is usually approximately calibrated at 6dB so for example the difference between S5 and S7 is 2 ‘S’ points so 12dB.

The difference between 10W and 300W is about 14.8dB which is a big increase to your signal if using the same antenna. Now let’s say for example you run the amplifier at a moderate 250W by reducing the input drive. The difference between 300W and 250W is less than 1dB which when you compare this to 6dB for 1 ’S’ point is actually very little and as the amplifier is not running at maximum power will generate less heat, and produce a cleaner output with less distortion that will actually make a difference at the distant receiver.


RM Costruzioni Elettroniche srl Guarantees that this product is free from manufacturing defects both components and workmanship for a period of time specified by the law. The warranty commences on the date of purchase. Any work undertaken for the warranty must be carried out by RM Costruzioni Elettroniche srl or an authorised service centre. The costs of transportation, duties and insurance between the client and RM Costruzioni srl or the approved service centre are the responsibility of the client.

The warranty must be requested to the distributor or reseller where the amplifier was originally purchased.

In the case where the original distributor or reseller no longer exists or deals with RM products, RM Costruzioni Elet-troniche srl will communicate the nearest distributor or reseller to use, or in the instance where this is not possible or convenient, RM Costruzioni Elettroniche srl will honour the warranty directly.

If any repairs are carried out outside of an approved service centre this will void the warranty and RM Costruzioni Elettroniche srl will not be responsible for any incurred charges. The warranty will only be honoured if the amplifier has been used for its intended purpose as described in this user manual, that the amplifier is returned with its original purchase receipt, returned in its original packing container, that the serial number is readable, unchanged and that the warranty seals remain intact.

The warranty does not cover the MOSFET power transistors or any aesthetic damage.

Any change to the warranty either by local law or that made by the distributor or reseller directly with the client will be the sole responsibility of the distributor or reseller and not by RM Costruzioni Elettroniche srl. In the event of any argument between parties resulting in legal action. It will be agreed to be settled in a court of law in Bologna (Italy).

The purchase of this product assumes that the client has accepted the terms and conditions of this warranty

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