PopularFX
Home Help Search Login Register
Welcome,Guest. Please login or register.
2021-12-07, 12:18:51
News: Registration with the OUR forum is by admin approval.

Pages: 1 2 3 4 [5] 6 7 8
Author Topic: "RF and molecular bond breaking Kanzius style"  (Read 103469 times)

Group: Moderator
Hero Member
*****

Posts: 2461


Buy me a beer
Hi Itsu

no more active I'm afraid, sold all my equipment some years ago after a divorce, only held onto a 2mtr hand held for repeater access. I used to be on HF with a yaesu 101, also 2mtr and 70cm for satalite work which I liked a lot, did try moon bounce at one time, and of course well known for speaking to shuttle crew when in orbit "many many years ago"

Changed my G4 for a Spanish license and held onto my G6 in England, been living in Spain for 25 years now.

Spent a lot on equipment over the years, 10 meter when the sun spot activity was high was really great, had many contacts around the world including royalty of the oil type, not to mention names ;)

The internet has made some people change, radio was a challenge not like today.

73's

-- .. -.- . 8)


---------------------------
"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.
   

Group: Elite Experimentalist
Hero Member
*****

Posts: 3270

Mike, 

thanks for the info, sounds familiar  :)

I was mostly in for 2meter DX (long distance) via Aurora reflection, Sporadic E-layer reflection (Es), Meteor Scatter reflection (ms), tropospheric conditions (tropo)
and did a fair amount of moonbounce, mostly with the big guns from the US/Canada

It was magic to hear your own reflection coming back from the moon after about 2s.
Nowadays they use computer aided programs to "listen into the noise" and show the morse signals on the screen  :o


I am thinking of reinstalling a station (FT-991 looks nice) now i have some extra free time.


Regards Itsu

   

Group: Moderator
Hero Member
*****

Posts: 2461


Buy me a beer
Mike, 

thanks for the info, sounds familiar  :)

I was mostly in for 2meter DX (long distance) via Aurora reflection, Sporadic E-layer reflection (Es), Meteor Scatter reflection (ms), tropospheric conditions (tropo)
and did a fair amount of moonbounce, mostly with the big guns from the US/Canada

It was magic to hear your own reflection coming back from the moon after about 2s.
Nowadays they use computer aided programs to "listen into the noise" and show the morse signals on the screen  :o


I am thinking of reinstalling a station (FT-991 looks nice) now i have some extra free time.


Regards Itsu



I would like to set up again but wanting to sell the house and move to a smaller one down by the sea, no money at the moment, times are quite hard here, I retire next year but my wife will continue as she is only 56, so things won't change that much. I am 45km outside Valencia, up in the mountains, would be a good site for DXing.

regards

Mike 8)


---------------------------
"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.
   

Group: Moderator
Hero Member
*****

Posts: 2461


Buy me a beer
Hi Itsu

that is some rig, I have not been keeping up over the years, talk about all included (apart from a 25amp PSU). The touch screen might be a bit small, there are a lot of comments about it, some good some not so good, but that goes for everything these days.

I find one problem with all in one, when you have a fault you are off the air on all bands :(

Oh to be able to afford one, @ 1700$ it is way out of my pocket now. Years ago I had no problem, when I was 35 I probably had 6000 pounds sterling in equipment, different times, different place and a lot of water under the bridge :'(

If you buy it and are throwing out the old ;)  I could recycle it ^-^

regards

Mike 8)


---------------------------
"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.
   

Group: Elite Experimentalist
Hero Member
*****

Posts: 3270

Thanks for the info Mike, i was in the same boat as you 10 years ago, i also sold my stuff then, only have my IC211E for 2 meters.

Enjoying the nice weather here while waiting for my FG to return   :(

Regards Itsu
   

Group: Moderator
Hero Member
*****

Posts: 2461


Buy me a beer
Thanks for the info Mike, i was in the same boat as you 10 years ago, i also sold my stuff then, only have my IC211E for 2 meters.

Enjoying the nice weather here while waiting for my FG to return   :(

Regards Itsu

Just poped in, we have arrived in France, was a very hot drive up here, at one point around Lyon a hot 44c wind and a good job we have A/C in the car.

Hope your SG comes back soon, will keep poping back in, though I can't get the hang of these French key boards, takes me for ever to type with them C.C

regards

Mike 8)


---------------------------
"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.
   

Group: Elite Experimentalist
Hero Member
*****

Posts: 3270

SG is back, so i ran a quick test on 13.56MHz with the new IXRFD630 driver and the old FQA11N90C (2) MOSFET's.

While on 4.5MHz this combo is very stable and reach efficiencies in the 90% range, on 13.56Mhz its highly unstable.
Blew one MOSFET and cannot get high output (70W with 24V drain voltage)
Also the current pulled by the driver (800mA at 4.5MHz) increases to 2A on 13.56MHz (similar behaviour as with the older driver IXDD414ci)

It could be my 13.56MHz module, especially the output coils which get hot quick.
Perhaps new output coils of thick litz wire are needed, but it also could be that the MOSFETs simply are not able to handle 13.56MHz.

Screenshot shows gates signal (yellow) and input from SG (blue)


Regards Itsu
   

Group: Professor
Hero Member
*****

Posts: 2602
Blew one MOSFET and cannot get high output (70W with 24V drain voltage)
I don't think it is the frequency that killed the transistor.  The gate signal should not be oscillating like that.

It is hard to design a stable MOSFET circuit in RF applications...unless you have one of those ;)
« Last Edit: 2015-07-09, 23:42:47 by verpies »
   

Group: Administrator
Hero Member
*****

Posts: 3844


Buy me some coffee
That video is a fake LOL
No where in the video do they show the power supply drawing more than 55V @ 9.45Amps or 520 watts
   

Group: Professor
Hero Member
*****

Posts: 2602
That video is a fake LOL
No where in the video do they show the power supply drawing more than 55V @ 9.45Amps or 520 watts
That's unfair to NXP.
Note that this average PS input power reading is taken when a "mismatch unit" is connected causing a huge VSWR up to 125:1.
With such high VSWR a lot of RF power is reflected back into the amplifier, effectively decreasing its PS input power draw by the amount that is reflected back.

The full 1.2kW can only be transferred to the load and drawn from the PS,vwhen the VSWR is close to 1:1, meaning reflections are at the minimum and all energy goes to the load and stays there at the expense of burdening the power supply with that RF power, which is what the NRVD Rohde and Schwarz RF power meter indicates at 2m08s .

I worked with that power meter and probes and always found them to be very accurate.
An independent Russian engineer also tested the performance of this transistor with a Bird wattmeter (see this video) and he also got a similar output power reading to the NXP EE with the Rohde & Schwarz meter.

P.S.
NXP is a serious company that stands to lose a lot by making fake videos marketing-wise and lawsuit-wise.  Their customers are mainly engineers and any EE with an RF power meter could prove that their specs were fudged, if they were.
« Last Edit: 2015-07-10, 08:24:23 by verpies »
   

Group: Moderator
Hero Member
*****

Posts: 2461


Buy me a beer
I don't think it is the frequency that killed the transistor.  The gate signal should not be oscillating like that.

It is hard to design a stable MOSFET circuit in RF applications...unless you have one of those ;)

I agree with Verpies, there is something up with the gate signal, what does it look like at 4.5MHz? and is the drive to the driver at the same voltage? seems low at 3-4v, have not time to look at the spec, maybe later.

regards

Mike 8)


---------------------------
"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.
   

Group: Elite Experimentalist
Hero Member
*****

Posts: 3270

Changed the output coil to be made from litz wire (2mm thick), amplifier is more stable now, but efficiency still low, 290W in, 220W out (75%).

That litz wire is hard to solder  :o

Will do some more tests tomorrow.

Regards Itsu
   

Group: Professor
Hero Member
*****

Posts: 2602
That litz wire is hard to solder  :o
Do you burn off the insulation/enamel from the strands, or do you sand it off ?
   
Group: Guest
Do you burn off the insulation/enamel from the strands, or do you sand it off ?

If it is the "solderable" type, it still takes a lot of continuous heat, flux and patience to get a solid connection.  If it's not, lord help you prepping an end.
   

Group: Elite Experimentalist
Hero Member
*****

Posts: 3270
Do you burn off the insulation/enamel from the strands, or do you sand it off ?

I assumed its the "solderable" type, as sanding off each of the hundreds of strands is not doable.
As Matt says, it takes a lot of heat, but still then it does not really "flow".

I will try with my 150W iron.

Itsu
   

Group: Professor
Hero Member
*****

Posts: 2602
When I'm not in a hurry, I use brake fluid with methylene chloride and once the enamel softens I wash it off in acetone and dip it in an overheated solder pot and flux alternately and repeatedly.
« Last Edit: 2015-07-11, 12:11:34 by verpies »
   

Group: Administrator
Hero Member
*****

Posts: 3844


Buy me some coffee
most of the enamels are self fluxing these days, you just need the right temperature, too hot and it will burn making it very hard as it will slag up, solder pots are normally the best way as they have large heat mass and even temperatures, though that 150 watt iron you have should do it  O0
   
Group: Guest
I do both, first burn with a flame from a cigarette lighter, and then sand with 400-grit. Then re-bundle and pre-tin before actually soldering to the circuit.
   

Group: Tinkerer
Hero Member
*****

Posts: 1524
I do both, first burn with a flame from a cigarette lighter, and then sand with 400-grit. Then re-bundle and pre-tin before actually soldering to the circuit.
Cool - that's the same way I do it.
   

Group: Elite Experimentalist
Hero Member
*****

Posts: 3270

Thanks all for your suggestions, my 150W iron did the trick, it will stiffen up the litz wire for about 4 cm (guess its melting the strands isolation) but then the top is solderable, kind of.


I worked this weekend on the 13.5MHz module, but it is not stable in the setup i have now.
I blew 5 MOSFETs including the 2 new DE275X2-102N06A's (which blew fairly quick compared to the FQA11N90's).
The present driver (IXRFD630) shows like the old one (IXD414ci) a current increase from 0.8A at 4.5MHz to 2A at 13.5MHz (even without a MOSFET), but is able to handle this 24W (specs say 100W), so it does not blow like the old driver (specs say 12W only).

So i guess i will continue on 4.5MHz, as with 82V/6.5A on the drain its putting out 500W.

Video shows 180W output at 41.3V/3.9A (drain) plus 12.5V/800mA (driver) plus 6Vpp 50% duty cycle over 50 Ohm from the SG input.

https://www.youtube.com/watch?v=bQlG4iBtZPc&feature=youtu.be

Screenshot is from this 180W and shows the SG signal (yellow), gates signal (blue) and the output signal (purple).

Regards Itsu
   

Group: Professor
Hero Member
*****

Posts: 2602
I worked this weekend on the 13.5MHz module, but it is not stable in the setup i have now.
I blew 5 MOSFETs including the 2 new DE275X2-102N06A's (which blew fairly quick compared to the FQA11N90's).
Did your scope show which MOSFET maximum rating was exceeded, eg.: VGS, VDS, ID ?
   

Group: Elite Experimentalist
Hero Member
*****

Posts: 3270
verpies,

no, it happens off course in a split second, its drawing the expected drain current, say 4 amps, then suddenly the amps goes up (into the current limiter set to 8A), but then its to late already.
Its always one of the 2 MOSFETs that is defective (not the same), even with the 102N06A's, which is a dual matched pair.

That suddenly can be by adjusting the frequency, the SG input voltage etc.
 
As the specs on this 102N06A says:

The DE275X2-102N06A is a matched pair of RF power MOSFET devices in a common source configuration.
The device is optimized for push-pull or parallel operation in RF generators and amplifiers at frequencies to >65 MHz.
VDSS=1000 V
ID25=16 A
RDS(on)=0.8Ω
PDC=1180 W

i doubt its the current or heat from it that kills it, also the voltage will not be that high, i suspect my output matching network is not adequate even with the litz wire.
I tune on low power for a nice output sine wave, but even then they drop like flies.

Itsu


« Last Edit: 2015-07-13, 10:10:28 by Itsu »
   

Group: Professor
Hero Member
*****

Posts: 2602
So either the VGS is exceeded or the 1000V VDS is.  Does Post Mortem ohmmeter measurement show the gate shorted or the drain shorted to source ?

Even the 1000V rating can be exceeded because of resonant rise in your LC network (due to bad tuning).  You should sine frequency sweep only the LC network to see its frequency characteristics - a lot can be gleaned from its amplitude vs. frequency plot.

Also, the voltage appearing on the drain influences your gate waveform through the Miller capacitance and/or the power supply line.  The distinguishing characteristic of RF MOSFETs is a very sensitive gate ( low VGS(TH) and VGS ).

   

Group: Elite Experimentalist
Hero Member
*****

Posts: 3270

All defective MOSFETs show a short from gate to drain and gate to source and between drain and source.

The 102N06A's both have their left MOSFET blown that way, the right ones look still ok.


Itsu
 
   

Group: Professor
Hero Member
*****

Posts: 2602
All defective MOSFETs show a short from gate to drain and gate to source and between drain and source.
No asymmetry, so that does not tell us much.

Any alteration that decreases these ~40MHz gate oscillations is in the good direction, because some of these ~40MHz peaks can get above VGS during the fault.  These alterations should be tried at low power, of course.
   
Pages: 1 2 3 4 [5] 6 7 8
« previous next »


 

Home Help Search Login Register
Theme © PopularFX | Based on PFX Ideas! | Scripts from iScript4u 2021-12-07, 12:18:51