This amplifier uses the latest ldmos devices from NXP. Designed for 1kw cw and 1.5kw pep ssb. Construction details on my website. I have these amplifiers for sale on my website. qsl.net/kf8od
now we are getting 65V LDMOS fets .less amps. start looking for 60V switchers . love the amp. and ldmos is class a type amp. that the bias control. the 65V is plug play. no re tuning. you are going to have a lot of fun talking on all the bands. I have tube amps. not today 90F. maybe winter!!
Alan - you could also use an external PS and an external LPF and make the amp enclosure as small as feasible and the amp enclosure would still be almost empty. That's what I do. That way I can just reuse my PS and LPF for every amp I make. But on the other hand, lots of people want a complete amp in a box, and I totally [almost] understand that too. :)
Hey thank you so much, it is the result of two year of really hard work to make this crazy design. You too, you should have the first price !! I didn't know that this challenge was Amateur Radio oriented.
KF8OD, Very nice amplifier. I am trying to settle on a design for a full legal limit mobile amplifier with 5 parallel boost supplies mounted close to the batteries under the hood of my 2019 F450. However it will likely end up on the other side of the the fender skirt as there is not much open space left under the hood. There should be plenty of space for the amp behind one of the back seats. I haven't settled on which LDMOS device to use, but am going to do it with a single push pull circuit. I was planning to utilize feedback in the circuit to improve linearity, but saw notes by other builders advising against it due to the possibility of causing the circuit to go into oscillation. However, I noted that you utilize feedback. Did you utilize circuit modeling to find the correct components or do it by trial and error? Ever lose any parts due to the circuit going into oscillation? Any advice would be appreciated. Thanks in advance WD0DIA
Feedback does nothing for linearity, LDMOS devices are not linear. I have never experienced oscillation. The feedback really only tames the gain on the low bands and keeps the rf input pretty uniform across 1.8-54mhz.
Very nice amp.I love these devices. I want to use the new 65 volt version of the device. I just completed a 75 amp 55-65 volt variable power supply for the project..next is the RF deck. Do you have a pcb set available for purchase? Or even a pcb layout? I am also interested in the transformer and choke parts. The pcb/engineering design kit from the mnfg is ridiculously priced. I want to use 2 devices and let it loaf. I’ve been using an 8877 for years. I had enough of tubes. Time for LDMOS Thank you.
Are these devices sourced from AliExpress or somewhere similar? I am asking as I do not see NXP on these. If yes, what's your experience with these suppliers? BTW, like your neat construction technique.73's
For anyone trying to figure out the efficiency and thinking Wow 40a @50v 1000w and thinking that isn't very efficient... Remember these are LDMOS Chips... they really don't start getting efficient until you get up to about 50-65% of its rating( theoretically 3900w@65v )... he's only running them at a 1/4 of what their capable (not including losses).... No, I don't advocate running anything at max but whenever he gets close to 2k that efficiency is going to come up quite a bit. Just thought I would throw that in there
@@KF8OD1 I figured you already knew about it when I posted it...I was just posting it for others that noticed the amperage vs Wattage. And then think the chip wasn't very efficient... I was just clearing that up for them... I remember when I first fired up a blf188xr and just through a few milliwatts into it I only got something like 14% efficiency... people used to silicon transistors don't understand that until they are putting appreciable power in the input into a Mosfet the efficiency is way down.... and is actually hard on the chip itself... better to lower the voltage a few volts with ldmos..
Hi Filipe, My opinion, operating ldmos devices at 50% yields better IMD. You can't dissipate the heat generated operating them at full output. Be conservative and they will last. The ratings on the datasheet are in pulse service.
MRFX1K80H is 1.8kW CW. With very good thermal management, this is obtainable... if device is run in good efficiency conditions. This device is used in laser, heaters, MRI, FM broadcast.
Hi Mike I've asked this before but do you feel a need to run your amps with LPF? If you operate on the air without a low pass filter do you notice a difference? Eric
