MOSFET RF power amplifier design

[Buddhafollower]

You know, i do not have a Bird or a Daiwa or another RF power meter. How can i measure RF power using the oscilloscope?

[spacecase0]

do you have a good RF resistor that is 50 ohms and can deal with the appropriate amount of power ?
if so, connect it, look at voltage and calculate from there
if trying to buy that resistor, most people call them a "dummy load"

[Buddhafollower]

OK, thank you. Yes i have a couple of them. 50 ohm at 250W RF

[Buddhafollower]

I have been working at a few high frequency power amplifiers with bipolar transistors, BJT's. Tonight i have finished one of them, the second one, and i have also improved the one with 2SC3264. Tomorrow i will post pictures of them and the schematic diagram i used.
I am also working on another one, this time way smaller, also a power amplifier but with BD139. A class AB RF power amplifier with this transistor. I think that the power will be 12.5W because this is how much a single one has.
If up to now i used MgZn ferrite materials, then with this one i will use NiZn material for a higher frequency of operation (a minimum of 1MHz). I didn't have material 43. I have to buy from Mouser. Sooner or later i will because i have to open a bank account and get a debit card which i honestly hate so much.... but i will have to do this also just for the sake of science.

[spacecase0]

some of the smaller companies will let you mail in the money to them,
here is where I got my type 43, but not sure if they have any right now
https://www.goldmine-elec-products.com

[Buddhafollower]

I can't use your web site since i live half a world away in Eastern Europe.

These are the two amplifiers i have been working on lately. The one with 2SC3264 you already know of but i have it's schematic diagram here and you can see it has been improved.
The second one is a very special one for me. It works very well up to 9MHz which is more than enough for me. The ''experts'' in my country were always unable to provide such schematics so i could build the amplifiers. I had to come up with designs in order to have my desire fulfilled.
I swear my people are w huge waste of my time....
BU526A8 is an RF transistor which has a transition frequency of 10MHz. So this amplifier is very good up to 9MHz. It has a beautiful sine wave but you have to follow the design well.

[Buddhafollower]

Maybe you can find time to continue sending the book to me.

[spacecase0]

I am sorry,
I have been quite sick but I am getting better now
and my electricity came back on last night, so it should not be to long.
I also have water issues, parts are on order to fix the well system, but will not be here till the end of the month.
doing things by hand takes half my day until I can automate it again.
I have the book right here, I see it at least 5 times a day to remind me.

[Buddhafollower]

Thank you very much sir.
And i hope you are alright.
Way too many problems lately, not just in USA but the world in general. It s impossible for something evil not to happen soon....

[Buddhafollower]

Let us say we have a Tesla transformer with a resonance frequency of 1.35MHz. The transformer is cylindrical in shape and has got 727 turns of copper wire 0.35mm in diameter. The primary coil has about 20 turns and an inductance of 8 micro Henries.
My question is how can i adapt one of the amplifiers above to work with this transformer and to manage to power it up? Even more, how can i get it to work so i can transfer power and information between two such transformers that are electrically identical?

Thank you,
Michael

[spacecase0]

not sure if this page will help.
https://www.teslascientific.com/products/free/

you likely need a capacitor with your primary coil to change the impedance to match your amplifier.
most people use what they call an antenna tuner.
and you will need to check the reflected power, most people use an SWR meter. but you can tune it by measuring the heat on your power amplifier, just go for the lowest heat on your heatsink.
here are a few to look at, not that you are going to buy either, because they only go down to 1.8MHZ, so not sure they would work for you anyway,
but the downloadable instructions also have full schematics (or they did last time I checked)
https://mfjenterprises.com/collectio...oducts/vc-300m
https://mfjenterprises.com/collectio...ucts/mfj-16010
hint, if you put the capacitor in series with the coil it will be easier to tune on the transmit side, but you will get more interference on the receive side, so use a parallel capasitor on receive and transmit or just only on the receive. (I have no idea if you are wanting 2 way communication or just one direction)

as far as encoding information,
the keyword you are looking for is "modulation"
are you looking to transmit audio or digital computer information ?

this might help
https://vu2nsb.com/radio-systems/rad...al-modulation/
or this
https://vu2nsb.com/cw-digital-radio/

because of the high voltage you are likely to get at least tiny sparks, so you are likely going to need to avoid using amplitude modulation or single sideband as the sparks are going to create horrible interference.
CW (morris code) should work just fine, frequency modulation might work.

[Buddhafollower]

Here is another amplifier built by me yesterday. It's sine wave is very beautiful but because i didn't have material 43 i had to use something else from Kemet. It is a high frequency core and it answers to frequencies from about 5MHz up to 300MHz. So this amplifier, though it is very small, only 12.5W, would have been very good to act as a driver for bigger ones, can't be used from 1MHz up to 5 because of the transformers. I have to get a bank account and a debit card and buy material 43 from Mouser. As i said it's sine wave is beautiful but from 5MHz up. It's schematic diagram is the same as for the one that uses BU526 but in this case the transistor is BD139 and the biasing resistor has the value of 47kOhm and an idle current of 40mA. The supply voltage is 15.5Vdc. I placed a 3W biasing resistor to last a lifetime

[spacecase0]

looks like you are getting things working, good to see

[Buddhafollower]

Please excuse me for being so bold but i would like to know if everything is ok and if you can continue sending me the book. If not then i guess it s ok. We live in very crazy times anyway. Good, delicate and sensible people have all kinds of troubles these days. May God give us Wisdom.

[spacecase0]

I started taking pictures of the pages yesterday
they did not turn out well
I had just got over the second covid when it seems my girlfriend has infected me with something else.
at least this seems to just be a regular cold, but I am still shaking from it.
I need a stand to digitize books...
anyway, I have not forgotten about the book.