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Author Topic: "RF and molecular bond breaking Kanzius style"  (Read 102627 times)
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Looks complicated to get everything connected properly.  Have you guys considered maybe getting one of these evaluation boards to simplify the work a little?

http://www.ixyscolorado.com/index.php/ixys-rf/mosfets-drivers-diodes-power-modules/evaluation-boards
   

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Looks complicated to get everything connected properly.  Have you guys considered maybe getting one of these evaluation boards to simplify the work a little?

http://www.ixyscolorado.com/index.php/ixys-rf/mosfets-drivers-diodes-power-modules/evaluation-boards

That would take the fun out of it ;D

Matt in reality it is not that complicated when you think of what it does. The part that takes a little time is the tuning so as everything flows as it should. That board is a complete frequency generator as well, also it has an output that we may change as and when we have our delivery (antenna) worked out, as we maybe don't have a 50 ohm impedance delivery, all a bit trial and error to start with at very low power so as not to burn up an expensive RF mosfet.

I myself am playing with cheap mosfets to see which will work at the 13.56MHz frequency or half that 6.78MHz which is also a scientific paired frequency with the mili: until I have the delivery sorted out.

regards

mike 8)


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I myself am playing with cheap mosfets to see which will work at the 13.56MHz frequency or half that 6.78MHz which is also a scientific paired frequency with the mili: until I have the delivery sorted out.

On a side note, I just found out today an IXDD614 and IRFP460 can go to 4.6MHz pretty easy driving a Tesla coil.  Not nearly the power you guys are after, but enough to give me a nasty little RF burn.
   

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On a side note, I just found out today an IXDD614 and IRFP460 can go to 4.6MHz pretty easy driving a Tesla coil.  Not nearly the power you guys are after, but enough to give me a nasty little RF burn.

Yep, up the drain voltage to near the mosfet max and see the power :D

RF Tesla coils are fun and silent unless you modulate with music and they can be a very good HI FI ;)

Carefull with the RF burns, they hurt for a long time.

regards

Mike 8)


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Today i completed my 1KW dummy load.

Its a 5 liter can filled with 4 liters of mineral oil, see picture 1

Inside is a 100W induction free 50 ohm Globar resistor, see picture 2

I have a temperature probe in the oil to monitor the oils temperature (180 °C max.)

Hopefully this will lengthen the test time.

Rigol FG is still out for repairs, so no testing possible right now.


Regards itsu
   

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Nice going Itsu

will be interesting to see how it performs O0

regards

Mike 8)


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While waiting on the return of my Rigol FG, i was doing some modifications on the amplifier.
I changed the old MOSFET driver IXDD414ci by the new IXRFD360 to see if it can drive the 2 FQA11N90c MOSFETs up till 13.56 MHz.
I also changed the MOSFETs choke by a T200-2 (amidon) toroid with 40 turns giving me 24uH as the old choke (3 turns @ 40uH) got hot.
As my present little FG does not go higher then 5MHz, i could only test with the 4.5MHz module.

It does work as my Bird wattmeter shows 220W @  41.3V/3.9A input (plus another 12W for the driver and 8W from the FG).
But the output signal is not the nice sinewave i expect, so guess i have to wait for my Rigol to return for doing better testing.

Video here:  https://www.youtube.com/watch?v=HIE1ukOm5HM&feature=youtu.be

Output screenshot below.

Regards Itsu
   

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Hi Itsu

Have not looked at video yet but I would say your inductance is too low, should be 40uH min for your choke, this does not only stop RF returning to the supply, but also is part of the tuning circuit. Will look more tomorrow, very hot here 40c and going to bed, but probably not be able to sleep with the unusual heat.

regards

Mike 8)


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As a general rule, the most successful person in life is the person that has the best information.
   

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Mike,


Quote
but I would say your inductance is too low, should be 40uH min for your choke, this does not only stop RF returning to the supply, but also is part of the tuning circuit

is it ?  I wonder, as in the severall E-class amplifier designs for the different frequencies (4.5, 13.56Mhz,  80 and 40 meter bands etc.) i see the same value (40uH).

Also, my present 24uH choke might be somewhat low for the 4.5MHz module (678 Ohm reactance), but at the planned 13.56Mhz it will be 2KOhm.
Found out that my present little FG is putting out rubbish at the 4.5Mhz, so somehow also this FG is toasted  :(
Guess that is the reason for strange output signal, so have to wait for my Rigol FG to return.

Its also unusual hot here (38°C ), so not going to do much as well.


Regards Itsu
 
   

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Mike,


is it ?  I wonder, as in the severall E-class amplifier designs for the different frequencies (4.5, 13.56Mhz,  80 and 40 meter bands etc.) i see the same value (40uH).

Also, my present 24uH choke might be somewhat low for the 4.5MHz module (678 Ohm reactance), but at the planned 13.56Mhz it will be 2KOhm.
Found out that my present little FG is putting out rubbish at the 4.5Mhz, so somehow also this FG is toasted  :(
Guess that is the reason for strange output signal, so have to wait for my Rigol FG to return.

Its also unusual hot here (38°C ), so not going to do much as well.


Regards Itsu
 

Hi Itsu

that is a strange output, is it the same direct at the output of the SG? in other words an amplified copy?

There seems to be a wide tolerance for the RF choke, that is between 40uH and 200uH, most of the calculators include this in their calculation for the output, that's why I was wondering, especially with that ghosting!

Drink plenty of water in this heat, off to the north of France next week for 10 days with my father in law in the champagne area, long drive for me at my age (64) 12.5hrs from Valencia with stops for food etc.

He has internet so I can look in O0

regards

Mike 8)


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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
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As a general rule, the most successful person in life is the person that has the best information.
   

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... for your choke, this does not only stop RF returning to the supply, but also is part of the tuning circuit.
I think so too, because if this choke was only for filtering the power supply and stabilizing the drain voltage then the capacitor would be connected like marked in red color on the schematic below.



P.S.
If the other coils were also wound with Litz wire then the power of this amplifier would be higher because at 13MHz the 50% skin depth in those copper windings is only 12.5µm.
Also, the copper laminate is too close to some of the windings and eddy currents in the laminate must be causing unnecessary losses.
   

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I think so too, because if this choke was only for filtering the power supply and stabilizing the drain voltage then the capacitor would be connected like marked in red color on the schematic below.



P.S.
If the other coils were also wound with Litz wire the the power of this amplifier would be higher because at 13MHz the 50% skin depth in those copper windings is only 12.5µm.
Also, the copper laminate is too close to some of the windings and eddy currents in the laminate must be causing unnecessary losses.

Hi Verpies

Never seen litz wire used at these powers, 1/8"" copper tubing yes, and even 1/4" tubing, we are talking a Kw here at some very high circulating current if the supply voltage is cranked up, and just one mosfet :D

These amps are very efficient, can be 90+%

I have a PDF written by the inventor somewhere, I will post it when I can find it.

regards

Mike 8)



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Here it is O0

regards

Mike 8)


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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
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As a general rule, the most successful person in life is the person that has the best information.
   
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Here it is O0

Very interesting paper Mike.  Big thanks!

Right off the bat the author mentions never allowing the transistor to see high voltage and high current at the same time, sounds great in concept, but he actually shows how the load network performs this function.  Yet the load does see the amps and voltage at the same time (I think), or if it does, that would be my definition of OU right there.  Being able to split current from voltage and then reassembling it at the point of use.

Good stuff.   O0
   

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Mike,

Quote
that is a strange output, is it the same direct at the output of the SG? in other words an amplified copy?

well, the input is square wave (sort of), but the downward side of the pulse is jittering, and this jittering we see
in the output, but then sine wave like (because of the output tank circuit).

Thanks for the PDF, the Fig. 2 confirms like you and verpies said that the choke is part of the output circuit:



verpies,

Its hard to use litz wire as the output coils are air coils and need stiff copper wire, perhaps when i use some former.
Not sure what you mean by laminate, i guess the copper back side?   If so i can fix that by relocating the toroid.


Thanks,    Itsu
   

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oops Matt, i did not notice your post with the same picture  :)

Anyway, i reinstalled my 3 turn 40uH choke, but the output signal stays similar crappy as with the 24uH choke, so i really think its the FG causing this.

Regards Itsu
   

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Never seen litz wire used at these powers, 1/8"" copper tubing yes, and even 1/4" tubing,
It is used in high power designs all the time.  A good source of it is a junked inductive cooker.  They also come in kW ranges
1/4" Copper tubing is good as a low loss rigid coaxial waveguides.

we are talking a Kw here at some very high circulating current if the supply voltage is cranked up, ...
Exactly, and a 0.02mm layer of copper cannot support high circulating currents well.

These amps are very efficient, can be 90+%
Yes, if they are built efficiently and the coils are tuned exactly to the operating frequency.
Class E amplifiers are tuned narrowband amplifiers - they are not wideband amplifiers !
« Last Edit: 2015-07-04, 23:17:17 by verpies »
   

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Its hard to use litz wire as the output coils are air coils and need stiff copper wire, perhaps when i use some former.
Yes, a thin plastic former compensates for the lack of stiffness

Not sure what you mean by laminate, i guess the copper back side?  
Yes.  It's enough to put some thick plastic or glass/ceramic spacers between the outside windings and the "copper back side"
Note that on that famous visualization below, there is a magnetic field outside of the solenoid....especially near the windings.
   

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Ok,  the choke is now clear of any copper bottom/back side by 1cm.

Quote
Class E amplifiers are tuned narrowband amplifiers - they are not wideband amplifiers !

I understand we want to modulate the 13.56 Mhz output with an around 40 Khz signal within the output bandwidth of this class-E amplifier.
If this will have no effects, we might need to go for a broadband amplifier approach.

Thanks,  regards Itsu
   

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I understand we want to modulate the 13.56 Mhz output with an around 40 Khz signal within the output bandwidth of this class-E amplifier.
40kHz frequency deviation is only 0.03% of the 13.56MHz carrier so it fits well into the bandwidth of such narrowband amplifier .
   

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Hi Itsu

Have you taken into account the new mosfet capacitance along with the C1 capacitance, it was just a thought I had just now, just maybe if this mosfet capacitance is higher, then you could remove C1 all together :-\

I'm trying to write up the principles of what we are trying to do here with a bit more explination, such as the carrier frequency does not really react with what we want, it is the modulation frequencies that are of interest at high power (DSB-SC) that is double side band (modulation frequencies) and (SC) suppressed carrier.

We might then get a little more help, I know ION is a ham too, along with being a very good EE :) who else is into radio here? come on own up ;D

regards

Mike 8)


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The other thing after looking again at the wave form, it maybe gate phase modulation, in which case it is the SG :-\

regards

mike 8)


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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860

As a general rule, the most successful person in life is the person that has the best information.
   

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Mike,


Quote
Have you taken into account the new mosfet capacitance along with the C1 capacitance

as explained in my post #81 and in the video, i have only changed the new driver.
The MOSFETs are still the 2  FQA11N90C's.
That way i want to look if the problem reaching 13.62MHz is the driver or the MOSFET's.
But as i have no reliable FG, i have to wait.
I did try without the C1 on the 13.56Mhz module, but it did not improve, the problem stayed with the driver (ixdd414ci) pulling to much current on that frequency

I think the MOSFET's will be ok for 13.56MHz, so we won't need the more expensive one.
Another test could be to use 2 drivers (ixdd414ci) one for each MOSFET like mentioned by verpies to see if then 13.56MHz can be reached, but i leave that test for another replicator  :P

Anyway, i am kind of stuck now without a good FG  :(

By the way, are you radio active  ;)  right now, and if so, on what frequencies?

Regards Itsu


   

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The below attached driver chip can be used up to 45 MHz.

Very interesting specifications.



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Thanks muDped,    but the DEIC421 is obsolete and replaced by the one i have right now,  the IXRFD630.

Regards     Itsu
   
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