
This is the home page of the A600 – my 2x MRF300 600W amplifier project for HF/6m, as initially described in this article. Here I will post the latest developments.
General features & specifications
- 1.8-54MHz coverage, 600W output, 20+dB gain
- uses a pair of low-cost MRF300 LDMOS transistors. These are proper RF power transistors housed in common TO-247 packages.
- onboard sensors for supply voltage, supply current, heatsink temperature, output power & reflected power. These are available via the Sensor Port and can be read directly by most microcontrollers, including most Arduino boards.
- connectors for an external bank of low-pass filters, so they are inserted between the amplifier and the output coupler
Downloads
Update – 2nd December 2019
- Published assembly instructions for the v1.2 kit, see above.
- LPF board is still under testing; the prototype achieves the desired attenuation but I’d like to improve insertion loss on a few bands before I release the design and make the kit available.
Update – 20th November 2019
- Assuming no further issues, the next batch of A600 amplifiers will be ready to ship in the first week of December. Includes some tweaks.
- I started working on a compatible Low-Pass Filter board. Should be ready early December.
- Still on track with the Control unit for mid December announcement. The hardware is almost done but sorting out the software takes time.
Update – 15th November 2019
A600 v1.2 kit was available to order here. Sold out in less than 8 hours so new batch on the way, hopefully by the end of November.
Updates – 14th November 2019
- This project has been awarded the 2nd prize in the NXP Homebrew RF Design Challenge 2019. Really appreciate the opportunity and congratulations to veteran Jim WA2EUJ and the Stanford University team led by Weston Braun for their results.
- Kits are almost ready but some parts are delayed due to courier issues. I plan to start taking orders in the following days and ship out after 20th of November.
- An advanced monitor, control and protection unit is in the works, featuring a large LCD touchscreen. ETA mid December 2019.
A600 version 1.2
- returned to original component references, as used on v1.0 PCB
- replaced T2 transformer with two separate coils (L2 & L3), 3 turns on ferrite cores. This improves efficiency and P1dB below 14MHz, but 1.8MHz matching is slightly worse.
- changed input network (C43, T1, R6 , R7) for better overall gain (around 24dB now) and better matching on 50Mhz. Input SWR is now below 1.5:1 on all bands.
- added 2k4 resistor in series with the bias compensation thermistor, as it was overcompensating. Quick test, heating the heatsink from 25 to 45C changed the idle current with less than 2%.
- fixed a few small mistakes in the schematic and rewired the Sensor Port to the correct pinout.


Very nice project Razvan.. congrats on results. Had some ideas to get similar power from mrfx600hr5, but your project seems to be a winner . PCB looks great, and just hope to see possibility of getting some form of KIT, or PCB for PA board.
Best regards!
Thank you Robert. Will let you know when kits are available.
I would like to know when they are available also.
73
This is an awesome project! I would definately be interested in a kit.
Add me to the list of hams interested in a kit. I would add an output filter to get that third harmonic (as described in the video) a little lower than -45 dB, but that should be easier.
Very nice. Do you have a kit. I would love to build.
Larry kd6eug
Looks great Razvan, thanks for your efforts! Also very interested in a kit.
Dave K4ZS
Sorry for the multiple posts, I was obviously doing it wrong at first. Please delete!
Thanks, Dave K4ZS
I too would like a kit.
Also interested in a kit! I’ve signed up for alerts too.
Awesome project, if it comes in a kit form I will be selling my children to purchase one.
Professionally done with a great write up. I’m very interested in a kit version.
Nicely done, clean efficient engineering. Thank you for sharing your efforts! I am looking forward to availability of a PCB and BOM. Curious to know if you be working up designs for t/r relay and or band pass filters for this amplifier design?
Great design, I’ll be very interested in a kit version, or even the pcb.
I’m very interested in a kit version.
Great design, I’ll be very interested in a kit version, or even the pcb.
BOM and PCB for me as well, even two 😉
Let me know, nice work.
I too would like a kit.
Also interested in a kit!
Would be interested in further developments too and if you will ever deploy a kit
Looks great, please add me to the list of those that would be interested in a kit!
Andrew G0MBL
Looks great I am also interested in a kit. Is there a mod so it works with a 10-15 w input?
Hi Ted. There is provision on the PCB for an attenuator, you’ll have to choose parts depending on the drive power you want.
Looks very hopeful for us less informed HAMS , several of the guys were talking about a two pallet amp. with a combiner for near legal limit , that would be great , best of all it would be nice to be able to deal in the English language , Thank You RaZvan .