Review of the RM Italy BLA 350 Plus Amplifier

If you already have 100 watts and 200 watts PEP output with the Yaesu FTDX10 and TS-480HX respectively, why would you still buy a 300-watt amplifier? The answer lies in full duty cycle modes like FT8 and RTTY. Both modes demand a lot from a transceiver’s final stage, something you definitely want to avoid damaging. Additionally, the TS-480HX has two rather noisy fans that kick in quite quickly at just 25 watts in FT8 or RTTY. So, I started looking for a small solid-state amplifier that could deliver 400 watts in RTTY without any issues.

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The brand held me back

There are several manufacturers that build 500-1000 watt solid-state amplifiers, but these were well beyond my budget, and second-hand models are quite rare. Then I came across the BLA 350 Plus, a 300 watt PEP solid state amplifier from RM Italy. However, the brand initially deterred me from purchasing the amp. RM Italy is not exactly known for reliable products, let alone good post-purchase support.

Close to my 400-watt goal

Nevertheless, I read predominantly positive reviews, with many users reporting that they could easily achieve over 350 watts of output, which would be close to my goal of 400 watts. And all of this for around 1150 euros. Still, I decided to wait until I could find a used amp from a more reputable brand, like Ameritron’s ALS-500 or ACOM’s 500S. But after waiting for over six months without any used models appearing on the market, and news that MFJ (the company behind Ameritron) had stopped production, Ameritron was no longer an option for me. When a promotion from WiMo in Germany came along, I decided to purchase the BLA 350.

Specifications and operation

The BLA 350 Plus comes with a built-in power supply. Two MRF150 MOSFETs do the work. According to the manual, this amp produces over 300 watts PEP on 10 meters and 250 watts PEP on 160 meters with just 12 watts of input. The BLA 350 has a low pass filter for each frequency band, which can be switched manually or automatically.

Keying the amp is done via a PTT input. There is also built-in RF sensing, which switches the amp with RF input, although the manufacturer strongly recommends using the PTT input. A simple menu allows you to adjust settings such as ALC and fan speed.

The back panel is simple with mains, antenna, transceiver ALC and PTT inputs. ALC can be set with a small flathead screwdriver. It only misses a terminal to connect the amp with a RF ground.

Back panel misses a ground terminal

Built-in safeguards

The BLA 350 Plus has some built-in safeguards. For example, the amp switches to standby if the input power exceeds 13 watts. However, this doesn’t mean you can drive the amp with 100 watts, as even a brief burst at 100 watts can damage it. Also, if the SWR is too high (between 2.0:1 and 2.5:1), the amp switches to standby. The LCD display then shows an error message.

Rather brief manual

The manual is rather brief, but it includes everything that should be there—well, almost everything. Unfortunately, it lacks a circuit diagram, which is a big downside for me, as this makes repairs difficult, whether done by yourself or others. If anyone has a service manual in PDF form, feel free to send it to me so I can make it available.

The power output

One advantage of a solid-state amp is that it has no tuning knobs and no warm-up time. This is also true for the BLA 350 Plus. Power in is instantly power out. Since RM Italy specifies a maximum input of 12 watts, I set the maximum output on the FTDX10 to 10 watts. I only pushed it to 12 watts briefly to test the output power.

Input vs. output power per band (take from the manual)

On 10 meters, the output was just under 350 watts, and on 20 meters, around 300 watts. When I tried testing on 40 meters, the SWR on my MFJ dummy load started rising sharply, grey smoke appeared, and that was the end of the dummy load. So, I don’t have any data for bands below 20 meters.

Power out on 20 meter band with 12 watt input

Noisy fan

This seems to be a common issue with many amps: a noisy fan. It’s less of a problem in digital modes, but more annoying in phone, adding background noise to your modulation. The BLA 350 isn’t much better in this regard. You can set the fan to run at a constant speed or in quiet mode, where it only kicks in when the temperature reaches around 38 degrees Celsius (100 degrees Fahrenheit). The fan then spins at full speed for a few seconds to blow out any dust and continues at a lower speed. If you have the amp nearby, the fan noise is quite noticeable.

This surprises me, as RM Italy could easily choose a much more quiet model. The placement of the fan and the exhaust slots on top aren’t ideal either, as the top of the amp always needs to remain unobstructed. A fan in the back panel would offer much more flexibility in terms of placement in the shack.

The top cover holds a 120mm fan, so you need to keep the top clear form obstructions.

Simple fan mod

A simple modification without any intrusive changes is to place a quiet 120 mm case fan (like one used for computer cases) on top of the built-in fan. By letting this fan run continuously, the amp’s temperature rises more slowly, and the built-in fan will kick in much less often. Once the warranty expires, I plan to replace the built-in fan entirely.

A very quiet 120mm computer case fan Xilence XPF.120 (4 euro) will keep the amp longer cool.

Reliability

Reliability is often a point of concern with RM Italy products. After using this amp for several months in various modes, I can confirm that there are indeed some reliability issues. The amp works perfectly as long as there are no error messages. In my case, the amp stopped outputting power when an SWR error occurred multiple times consecutively. Turning the amp on and off didn’t help. Only after leaving it off for several minutes did the amp produce power again. I have yet to identify the cause, but past week it didn’t occur anymore.

UPDATE 5th November 2024:
The above mentioned issue with the amp did not occur anymore.

Buy or not?

Is the BLA 350 Plus worth buying?

Yes, if you’re looking for an amp todo the heavy lifting in full duty cycle modes like FT8 and RTTY.
Yes, if you have a QRP transceiver and occasionally want extra power, as the difference between 10 watts and 300 watts is about 2.5 S-units or more on most S-meters.

No, if you already have a 100-watt transceiver and mostly use SSB, as the difference between 100 watts and 300 watts is less than 1 S-unit.
No, if you have a larger budget. In that case, it’s better to save up for a more powerful amp.