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Happy news today. Liberated Kherson! I really want to go home to my native Nikolaev! Sorry, couldn't resist.
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73, Oleh, UY2ZA

On Sat, Oct 8, 2022 at 04:20 PM, ajparent1/kb1gmx wrote:

That it works at all is pretty amazing.? Its still a bad solution.

As promised, I'll let you know. But I will upset the skeptics and report on the use of QDX with IRF-510. Power - 8 volts. Carried out about 600 QSO on 20 meters. The transmitter is working 66 countries worked on a modest antenna, 56 were confirmed in LOTW. The transceiver worked for several minutes transmitting without load due to my fault. I was scared, but everything remained working.
73, Oleh, UY2ZA

On Sun, Oct 9, 2022 at 11:08 AM, Oleh I2/UY2ZA wrote:

Thanks for the discussion. That's why we communicate.

yesss! I agree.
The strange thing here (slightly OT) is the bare fact, that the discussion "BS1780 vs IRF510" is dating from the past century, so to say from the mists of time.
Was there in the meantime no progress in the semiconductor field to discover something in-between the two, fitting like a BS170 but in a reasonable case with decent power dissipation??
Allas I am not an expert regarding the modern semiconductor market and this is why I raise this question in this group: not because I intend to troll towards yet another OT, but because I have a real interest in discussing and communicating on this level.

At least, in the last century we had the famous MTP3055 as an alternative for the IRF510, yielding better results for low voltage applications in the class AB&B sector. Do you remember the Index+QRP Rig? Has NOTHING to do with a grown up class E amp, but I am just trying to give an OT example. This device has been obsoleted and it seems that there is no alternative to it: I bitterly miss it.

On the other side there are so many educated ladies and gents in this group writing with tongue of wisdom about elevated things. Does any of them know anything about an alternative?

How about a bipolar device? Yes! I know: by being current driven as opposed to a MosFet it will eat Amperes (instead of Volts) and hence reduce the efficiency. And it will have thermical issues uncommon to the FETs.? But it would still be an alternative worth of being taken into consideration FOR ME. Any ideas dearly accepted. I have some pcb scrap, a bunch of transistors and would be eager to start experimenting, but because of not knowing where I am, I am unsure in which direction to start. If you say nothing, I promise that I will start with those good old 2N2222: at least they had a metal case and one could keep them cool with a fuse holder soldered on top ;-)

As for the TOPIC problem itself, let me explain my point of view: using BS170 (either 3 of them Class"E" style like in the QCX or 4 like in the QDX in Class"Hans"), my target is the range between 3W on 12Vcc and 2W on 9Vcc supply. Never get greedy for more than that and respect the "Socal soft landing condition" (at least for Class"E) well cheked and adjusted with help of some scope monitor. This way, regardless of the load offered to the PA, I have never ever succeeded to send the transistors up in smoke. I also like to "pair" the transistors after a method widely popular in the SoftRock times (static pairing), well knowing that matching FET transistors that do not display thermical runaway is not so important like for their bipolar cousins.? But not pairing them means literally:
"Best Horse Gets Most Beating"

Your mileage might vary, but I felt the urge of placing my footprint onto this thread, even if I expect many of a chest beating to occur as a consequence. And if it happens, I did not intend this: I am really interested in the wording at the begin of this message, a quote from Oleh's plea:?
"Thanks for the discussion. That's why we communicate."

Happy qrp ing! de dl2arl

Yes. I was wrong. Sorry
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73, Oleh, UY2ZA

Replying to Allison, from the original poster.

"I also had to adjust the band-pass filter. Reduced the number of turns by two turns of the inductor."


Geoff

A bit OT but, reading this thread, I feel necessary to thank the very knowledgable and patient people in this forum for their outstanding? teaching.
Vr
Giuliano, IV3DLW

Oleah,

IF the act08 is not running hot? (surface temp under 40-50C) and the finals are
at an acceptable temp (anything under 50C is fine)? Go make contacts and enjoy.

Solid state parts can run wam and most if you keep the silicon inside under 100C
will do so for a long time.??

The need to adjust L10 is understandable,? Its a filter and if the terminating impedance
changes the filter performance changes.? That will likely happen with L6 and L8
for the other bands.? The change is a result of using the IRF510s, neither good
or bad just the interactions that come from such a change.


Allison
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I can't see anything at all offensive in Allison's posts.
I've tried, I looked, and I looked again.
Nope, still can't find anything.
10-4 ?

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- 73 de Andy -

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73, Oleh, I2/UY2ZA

Geoff,

Yes, L12 is RX only.??

Whose question are you replying to?

Allison
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If you look at the handbook for the QDX, you will see that the PA transistors are not involved in the circuit for the band-pass filter. The PA transistors are used for transmit and the bandpass filter is used on receive.
Altering the number of turns on L12 will have no effect on the PA.

Luke,
Never confuse technical conversation for insult? and taking offense.?
Your comment is offensive.? I'm old?enough to be your mother.? My
comment is if you can't add anything useful, just don't.? Chill please.

As to the comment I could have sent parts, well why don't you as its far
from trivial to send even a few small parts overseas.??

Further:
As to class or D or E its a pedantic issue the IRF510 will not do
that either with ACT08 as driver.? ?Been there did that have the scars.
Both modes are dependent on saturating the device.? As I commented
its barely class B, marginal Class C.? The devices are not switching.?
I do know Harden's work well.? Have you read Yang and Rooij of
?EPC-CO.com as they took it to the next level.? I have used the
GaN devices for class D power conversion (wireless power transfer)
as part of a project.? We met several times. I discovered that TI has
the only suitable driver for any frequency above 7Mhz.

Its nice for Oleg that it puts RF out.? That he had to reduce supply
voltage to keep current down is an indicator of inefficiency.? He also
had to add cooling fins.? Excellent experiment. HE demonstrated
why we can't just drop in a higher power device and expect the same
or improved performance.

While its interesting to me it works I do wonder how hot the act08 is
getting.

Allison
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Come on friends. ?Discussion (like confession) is good for the hobby (and soul). ?Those who are more knowledgeable than me are welcome here in my book. ?Again, this is a hobby and for those who really want to know there is so much information (much open to different interpretation) to study and learn from. ?Keep the information and correction coming. ?My feeling are not damaged. ?Again, one may be using the incorrect terms but if one is happy with how it works and learns from it, it works! My wife corrects me many times but I still do things the same way, now with better understanding. We are both happy with the outcome.?

Thanks for sharing, Oleh! Good job adapting the parts you have on hand to get your QDX back on the air. 99% of operators wouldn't take the time or energy to fix their radio like this.

And to Allison - as my mother used to say "If you don't have anything nice to say, don't say anything at all". In the time it took you to write out those messages you could have easily dropped some replacement BS170's in the mail for the old man...

For those that are interested in learning more about? this subject, Paul Harden NA5N wrote a couple of very good articles way back for QRPp.? ?

Rolf
K9DZT

I believe that the PA is class D, not class E in QDX.
Gary
W9TD

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73, Oleh, I2/UY2ZA

Actually its actually worse as we are dealing with dynamic waveforms.

BS170 s 24 (max 40) PF per device input capacitance.? times 2 devices.
Also the Crss or reverse transfer capacitance is 7pf (10 max).

IRF510? the Cin is 135PF (for some can be as high as 180pf).? X1 device
The reverse capacitance? is 20pf? (for that vendor, others are higher)

You have both input capacitance (gate to source) and what is known
as Miller capacitance which is essentially negative feedback
(the actual Crss capacitance) multiplied by the output voltage swing
(simple description).? So with IRF510 your really about? four times
greater load to drive with a tiny CMOS gate.

With all that, it makes the IRF510 much harder to drive than BS179s
in parallel.? How much difference?? BS170s are saturated RDS_on is
the limiting factor for power.? For Irf510 the only reason power out
happens is for drive above he gate threshold it has a gain of 1S
so for 5V drive you get about 2-2.5V gate drive not allowing for
capacitive load and you can maybe get to 2A drain current but
it is not saturated power its linear.? If it were saturated the .54ohm
RDS_on would make for a lot of power.?

FYI the current drive needed to hard switch a IRF510 at 13.55 mhz
is about 8A peak for?6 volt (measured) drive. I needed a 10V pulse
but no devices existed.? I was doing class D power conversion.?
Where does that power (current) go?? ?Charging that gate cap
then discharging it while the Miller coupling is working against you.


Allison
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