70W Amplifier from eBay - Spinning my own Board

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70W Amplifier from eBay - Spinning my own Board

Рет қаралды 8,784

Күн бұрын

This video is a followup from my earlier video on the "70 Watt" amplifier from ebay
• 70 Watt Amplifier Kit ...
In this video I show a board I had created using the circuit from that amplifier together with some great mods from F5NPV
f5npv.wordpres...
The board schematic and gerber files are here
github.com/tha...
The bill of materials is here - let me know if you have any questions on the source of any component
github.com/tha...
Here's a link to those ferrite tubes on aliexpress
www.aliexpress...
I do a shoutout to kitandparts in the video - no affiliation but they are a great source for all your toroid and binocular needs
kitsandparts.com
0:00 Intro
0:40 Changes between my board and the original
3:15 Schematic walkthrough of the board
5:38 Walkthrough of the built up board
9:25 Input SWR testing
12:20 Testing CW through the amplifier
13:41 Look at the effectiveness of the LPF
14:34 Two tone test setup
15:12 Two tone on the oscilloscope
17:02 Two tone on the spectrum analyzer
20:46 Replacing the FT50-43 with Ferrite Tube
22:42 Replacing the FT50-43 with BN 43-7150
25:27 Wrap up (I didn't get to testing the RD16HHF1s - more to come)

Пікірлер: 31

@theovannieuwenhuizen5756 2 жыл бұрын

Thanks Ian, scientific research. Love to see the update with RF MosFets.

@na5y 2 жыл бұрын

Thank you Theo. Just finished the little adapter boards for the RD16s. Hope to get a new video out soon!

@antaf56 2 жыл бұрын

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

@na5y 2 жыл бұрын

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! ;)

@curtstacy779 2 жыл бұрын

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.

@na5y 2 жыл бұрын

Exactly Curt - I would say 99% of the "RD16s" on eBay and just IRF510s with some laser etching on the case. Thanks for the comment - glad you enjoyed

@mariovano 2 жыл бұрын

Great Stuff Ian! There's no such thing as too many experiments!! AE0GL

@na5y 2 жыл бұрын

Thank you Mario. I completely agree!

@alexhorvath1814 5 ай бұрын

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?

@na5y 5 ай бұрын

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

@ohmschool 2 жыл бұрын

Excellent work exploring each components impact on performance! 👍Curious to know if you measured dBc of 3rd harmonic before low pass filter was connected?

@na5y 2 жыл бұрын

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

@ohmschool 2 жыл бұрын

@@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!

@rocknroooollllll Жыл бұрын

Hello! That spectrum output at point 3 is a parasitic; you can see it also on the scope, if you know what you are looking for.

@na5y Жыл бұрын

Thank you for the comment. Anything generally you could suggest with this amp to reduce parasitics?

@mvssarma3387 Жыл бұрын

With common bias, one to to pre-match mosfets.

@pete3897 2 жыл бұрын

Thought I'd clicked on to one of Brek Martin's videos there for a minute! lol :) You two chaps sound _very_ similar to this kiwi... 73s ZL2FSK

@na5y 2 жыл бұрын

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" ;)

@datatransfer277 Жыл бұрын

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.

@na5y Жыл бұрын

I haven't unfortunately Data. I hope to get back into the amplifier again in the near future. Thank you for the comment!

@Tibetan1962 Жыл бұрын

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.

@na5y Жыл бұрын

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

@m1geo Жыл бұрын

Nice work! Subscribed!

@TeamSpeak-yv4yk Жыл бұрын

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.

@na5y Жыл бұрын

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

@mrtechie6810 8 ай бұрын

Why do you leave such long leads on the capacitors?

@na5y 8 ай бұрын

On the lowpass filter? Simply because I wanted to reuse the caps later on is all.

@macgyver5108 Жыл бұрын

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...🤨😅

@na5y Жыл бұрын

Heh - not many people outside Australia would have even seen it! Congrats on your sleuthing!

@macgyver5108 Жыл бұрын

@@na5y I have A.D.D. so I tend to notice EVERYTHING! Oh look, a squirrel?!🤪 😅

@macgyver5108 Жыл бұрын

@@na5y At least I didn't go excitedly run naked through the streets like Archimedes did eh...