Saturday, July 19, 2014

RM Italy HLA 300 Plus Linear Amplifier vs. the New RM Italy HLA 305v Plus Linear Amplifier

So What's the new RM Italy HLA 305v plus is different from the classic RM Italy HLA 300v plus?

The classic HLA 300 series amp still a very good amp!

The new HLA305 is the next generation of the HLA 300 series amplifier. New features include:

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  1. Larger Heat Sink. A new die has been designed that provides increased dissipation by about 25%, which in turn increases the internal PCB size allowing improved layout of some of the critical circuit components. This allows the amplifier to be used at higher duty cycles without the requirement for cooling fans. A version is also available with fans, that are now larger diameter and run much quieter than previous models. This will afford the contest operator a much quieter noise level.

  2. More linear input circuit. This improves the measurement of both frequency and input power.

  3. More powerful processor. Allows improved control of the amplifiers protection circuits and general functionality. In addition we have introduced a new system for digital to analogue conversion that allows measurement of all values at the same instant instead of se-
    quentially, (sample and hold). We have also added measurement of the input current and redesigned the SWR sensor circuit which is now done with a ’Tandem Match’ that results in better linearity and precision.

  4. LCD Display. The introduction of a more powerful processor allows us to use an alphanumeric display which is able to show the status of the amplifier and some of the operating parameters.

  5. Improved Filtering. The six Low Pass Filters have been completely redesigned and are now 5 pole Cauer designs. This has significantly improved the attenuation of the harmonic output. We also now use larger (AMIDON) cores that avoids core saturation and with the use of high quality Siler Mica capacitors that are better able to cope with excessive voltage in the case of a poor load.

  6. Redesigned RF stage. With respect to the old HLA300 we now use an adaption of a classic Motorola design which although more complex improves linearity with respect to frequency and reduces signal distortion. The collector supply is now provided via the feedback transformer so the DC supply is no longer passing through the output matching transformer which greatly reduces the possibility of core saturation.

  7. Bias Circuit. This has been completely redesigned and is now stabilised in both voltage and temperature to keep the bias supply constant with changing supply loads and transistor temperature.

  8. Faster RX/TX Switching. RX/TX switching time has been greatly reduced, (After band detection has been completed). 


  1. I have both the 300 and the new 305 (unfortunately the 305 developed a fault shortly after I bought it and I am still waiting on the outcome of service here in the USA). Using them side by side the 305 is a very real improvement over the 300. I still like both but the added features of the 305 and the fact it is FCC approved (better filtering) make it a worthwhile addition to my low power SDR radios. 73 from Waikiki - Bob KH6KG

  2. FLASH UPDATE - The RM distributor in the USA has sent me a replacement unit - now waiting for the new 305 to arrive. GREAT SERVICE RM! 73 from Waikiki Bob KH6KG