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
- 1.8-72MHz 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, drive 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
Resources
- Article: Choosing a heatsink for the A600 LDMOS linear amplifier
- Article: A 600W Low-Pass Filter Board for 1.8-72MHz
A600 v2.1 Amplifier Kit full assembly instructions
1 file(s) 2.31 MB
F600 v1.0 LPF Kit full assembly instructions
1 file(s) 790.42 KB
B1500 v1.0 Backpanel Unit Kit full assembly instructions
1 file(s) 638.48 KB
A600 v2.0 Amplifier Kit full assembly instructions
1 file(s) 2.51 MB
A600 v1.2 Amplifier Kit full assembly instructions
1 file(s) 2.87 MB
Update – 22nd March 2020
- The B1500 RF amplifier Backpanel Unit is now available. It features RX/TX switching, 2-port antenna switching, transceiver interfacing and has an onboard 12V DC-DC converter.
Update – 22nd February 2020
- After a long delay related to challenges with China logistics, a new revised version of the A600 Amplifier Unit is back in stock. v2.1 brings improvements in ruggedness and is available to order here.
- The Backpanel Unit is almost ready as well and will be announced soon.
Update – 24th December 2019
- LPF board kits are on the way and will ship after 6th of January; two thirds of the first batch are already gone. Can be ordered here.
- A new Backpanel unit is in the works. It will handle RX/TX switching, transceiver interfacing and includes a 12V/3A DC-DC converter and a 2-port antenna switch. Expected in the 2nd half of January.
- This has pushed the Control Unit further back. I know this unit is expected by many of you, but it’s worth the wait as it will support all the features added by the Backpanel Unit.
Update – 7th December 2019
- A600 v2.0 kits now available, includes multiple improvements. More details here, order the new kit here.
- LPF board sent to production, kits will be available soon.
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 .
Nice project. Do you have the Gerber-files available so I can order the PCB?
Sorry Fokko, no Gerber files available. But I offer kits with the boards pre-populated and it’s probably cheaper than you can make it yourself, check out the Shop area.
Hello Razvan are there any possibility to order the circuit boards only from you?
Hi Marko,
Sorry, only complete kits are available for now.
The output power exceeds the total Device Dissipation (272W), the ice becomes very thin here!
The efficiency is quite good on these new LDMOS, device thermal dissipation is around 200W.
Hi,
Input transformer (T1) 4:1 and
Output transformer in a ratio of 1:9.
Doesn’t this cause an impedance problem for transistors?
73
Not at all; there isn’t much interaction between the input and the output sections.
Typically, the FET input characteristic is equivalent to a very high value resistor (in the Mohms range) paralelled to a significant capacitor (~403pF for the MRF300). To achieve good broadband response, a low value resistor (10ohm on each gate is a typical value) is used to dampen the reactive effects of the gate capacitance. The input transformer has to match to the combined impedance presented by this resistor and gate capacitance and most of the drive power is actually wasted in the resistor(s).
The output matching is mostly related to supply voltage and desired output power, as the supply voltage limits the maximum amplitude you can have in the output transformer’s primary. Assume 50V supply; this will allow you about 96Vpp primary amplitude (a few V drop caused by FET RdsON) which equals to about 68Vrms. Step that up with a 1:4 transformer (1:2 winding ratio), you will get 136Vrms which is 50ohm is about 370W of output power; with a 1:9 transformer (1:3 winding ratio), the output voltage will be 204Vrms, or about 830W maximum RF power; for more than that, 1:16 (or two 1:4 in series) will be needed. These are not hard limits as the signal coming out isn’t a perfect sinusoid, but useful reference points. There are also some reactive components not taken into account (drain capacitance, transformer inductance, etc) for the sake of simplification.
Let me know if that makes sense. Cheers !
Hi,
Thank you very much for this significant information.
I understand better now.
Do you have any documents you would recommend about the calculation of these output transformers (1: 4 or 1: 9)?
It is not possible to find coax cables other than 50ohm here.
Is there any other way to do this?
Finally;
How to calculate the cable length of 1: 9 transformer and 1: 1 balun at the output?
thank you very much again.
73
The transformer type is called TLT, or “Transmission Line Transformer”. A Google search for “TLT RF power transformers” should come back with more detailed information.
You can paralel coaxial cable to achieve lower characteristic impedance; 2x 50ohm lines of equal lengths will be have 25ohm characteristic impedance, 3x 50ohm lines will have 16.66ohm etc. People typically use RG-316 in this case, but you will need larger ferrite cores to acommodate the extra wiring.
For the 1:9 transformer, ideally the coax length should stay under 1/10 of the wavelength at the maximum frequency of use; the shorter it is, the better the symmetry and the lower the reactive components.
For the 1:1 output balun, choking impedance is the most important factor. Make sure the cores provide enough at the lowest frequency of use.
Good design. Congrats. I will order a kit. Are the coax cables for the transformers in the kit? What is your delivery time?
Hi Peter. Yes, kit has all the electronic parts; you will need a heatsink, mounting bolts, thermal paste etc. These days I post twice a week, but there are some delays with the postal system. Usually it takes about a week to get to European countries.
Razvan.
I’ve been following your amplifier design Razan congratulations on a great kit. What control circuit do you use to monitor al the various functions?
Also do the on board connections of the amp board, filter board, and back plain connect together to control operation?
Thank you.
Yes, all the connection headers from each board connect to the Control Unit, which will be released soon.