Thanks a lot,very intersting and instructive video Ian. For sure with these mosfets, that are made for switching application, the intermodulation result is quite acceptable. I bought the same kit on a chinese site but I have not yet assembled it, however you confimend what I was expecting at the output of this amplifier. On the same site I also bought some "used" MRF9100 for about 10 euros each, I have intention to test them in place of the switching MOSFET also . Thanks again for the great video! Antonio
Thank you Antonio - I actually have some MRF186s on order to try the same thing. I like having the two mosfets in the one package! Of course they are from eBay so my milage may vary! ;)
Nice video! The RD16's that's what I ran into. Then I twisted things around to work. Then I blew a couple. Then I realized my chinese transistors were IRF510's marked RD16's they had a diode. I need to get back to it. So much fun.
Excellent work exploring each components impact on performance! 👍Curious to know if you measured dBc of 3rd harmonic before low pass filter was connected?
Thats an interesting question . I did have a look at the waveform without the LPF (it looked like a jagged square wave) but I didn't do any other measurements. I think I might do that in a followup. Thank you for the comment
@@na5y Yes this would be a very interesting follow up in future and thank you for considering it 🙂The 3rd harmonic for most types of FETs can be as high as -10 dB vs principle peak on spectrum analyzer (without corrective devices like drain to gate feedback resistors or LPF). Measuring amplitude of 3rd harmonic on spec analyzer without the corrective elements could help determine best way to tackle 3rd harm. thus maximizing performance. Super interesting stuff!
Well I am an Aussie - but a number of people have said I sound like a Kiwi. I have been in the US so long its sometimes tough for me to tell them apart unless they say "six" ;)
Thanks for this great video! I have already ordered the PCBs and now I am sourcing the SMD components, looking on mouser and digikey. Are there any minimum power requirement ratings you would say for resistors, capacitors, etc? I am just getting into RF and am not too familiar with which components are likely to fail... over current, over voltage etc. I am assuming the high power amplified side of the transformer does not have so many components and the lower power side has lower power so not as much of an issue?
There are a few components with a power requirement. The resistor on input (the two near the input transformer) were 3 watt resistors. The resistors across the FETs are 5W - I believe, going from memory here. The relays I got from ebay here www.ebay.com/itm/291739505384 - I hope this helps and good luck with your build
I am keen to try the board you have designed, have you done any further testing on it I think you mentioned you were looking to put a filter on the board. A 40/20 filter on the board would be great.
When you say T-50-43, is that what may more commonly be known as FT-50-43? Do you think an amplitude difference between the audio source tones might affect the amplitude discrepancy on the amplified output? Fantastic video BTW. Much appreciated.
Yes T50-43 should really be FT50-43. Certainly I am relying on the audio signal generator emitting pure (and equal) tones. Not only that - the audio generator itself isn't introdcuing harmonics. Testing that unfortunately is a little bit beyond my capabilities ;) - so I am trusting somewhat in Siglent here. The signal generator I am using is by no means top of the line - but I am hoping its good enough for this work! Thank you for the kind words and comment - glad you enjoyed
Hello NA5Y, I made some minor changes to the board layout but am a bit stuck on the bias feedback. Could we use a thermistor to change bias. Very interested in making this board and amp. Have you built a new version with any improvements you mentioned in the video. Great video by the way.
I was actually thinking of using a temperature probe like the TMP36 sensor and have it controlled by a microcontroller - but I never got around to it. I did do a video on the TMP36 but never took it further. Thank you for the comment
I was wondering what the flag was on your channel logo/icon (it's super tiny and kinda hard to tell at 1st). My first thought was the Swedish or Finnish flags but remembered they're the wrong scheme, plus your accent kinda immediately ruled them out. I couldn't find it for awhile, Google and the even more impressive Yandex image search weren't loading the image and kept coming up with zero results. Then I had what can only be described as an Archimedes moment... _"I found it!"_ AKA _"εὕρηκα!"_ Literally the Eureka Republic flag...🤨😅
