Re: strange behaviour of IRF MOSFETs
What may be forgotten and not checked is maybe the power drop is the driver(s) and prior stages.
Lets assume the gain of the finals is stable but the drive power falls...might the driving source be the cause?
Seems real RF parts also behave wrong.
I do a lot of work with "real RF" parts? and they will behave badly as well if provoked.
To the rest yes good heat sinking helps and bias feedback is desirable to support?
reliability.? Especially when the operating conditions are not optimal like high SWR
or sustained high power.
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Allison
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Please use the forum, offline and private will go to bit bucket.
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Re: sbitx v3 circuit and performance details
I have included rf voltages at various points to make it easier for folks to troubleshoot the PA chain. - f
I completed a comprehensive test of sbitx v3 using IRF510s and all the modifications and performance figures are in a document. To put it in a nutshell, the IRF510 PA provides 25 watts upto 10 MHz, 20 Watts to 21 Mhz, and 10 watts on 28 MHz. The power chain is very resilient and useful even for other projects. You can read the details on? The complete circuit diagram?(it is same as v2 except for a few resistors) is on?
- f
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sbitx v3 circuit and performance details
I completed a comprehensive test of sbitx v3 using IRF510s and all the modifications and performance figures are in a document. To put it in a nutshell, the IRF510 PA provides 25 watts upto 10 MHz, 20 Watts to 21 Mhz, and 10 watts on 28 MHz. The power chain is very resilient and useful even for other projects. You can read the details on? The complete circuit diagram?(it is same as v2 except for a few resistors) is on?
- f
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Re: sBitx V2 FT8 Problems
Ashhar,
I use a mouse cursor to select. The cursor is in the middle in state I, then the result is correct.
Other. Log input from the keyboard still doesn't work for me.
When it doesn't automatically create a log, I try to enter it and OK, there is nothing in the log.
I repeated this by rebooting and entering the data again, then OK and I still don't see any data in the log.
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Gyula HA3HZ
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Re: sBitx V2 FT8 Problems
The correct line is selected on mouse up, not mouse down. So slide the finger to the target line and lift the finger.
On Sun, Nov 19, 2023, 1:04 PM HA3HZ < gyula@...> wrote: FT8 works well with V3.
The problem for me is that it is difficult to select the line you want to reply to with the mouse cursor on the 7" screen.
You can read the change from v2 to v3 as I did.
One option is to enlarge the screen with the magnifier that I also use for soldering.
Another is the HDMI monitor. No picture was taken of the latter, but the magnifying glass is here.
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Gyula HA3HZ
ps.: in reality, there is no such distortion in the picture. the camera sees differently.
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Re: strange behaviour of IRF MOSFETs
I have noticed this even on LDMOS. i dropped AFT05MP075, a 75 watts LDMOS transistor in place of the IRFs. In this setup, there are no thermal pads. The LDMOS is directly soldered onto a small copper block that was bolted to the heatsink. That too exhibited this behaviour.? I also (dangerously) tried tweaking the bias while the output reduced, during transmission to see if the output level can be re established with bias change. That didn't work either. - f
On Sun, Nov 19, 2023, 1:51 PM K9HZ < bill@...> wrote: Whow about real RF transistors?
Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton - J68HZ Soufriere, St. Lucia W.I. Rent it:
email:??bill@... ? On Nov 18, 2023, at 10:45 AM, Joel Caulkins/N6ALT <caulktel@...> wrote:
?Farhan,
I know you have always preferred the IRF510s, but have you considered the IRF530s? I have noticed that most of the cheap Chinese Linear amps use them to get a good 45-50 watts. I just bought a Micro 50 Plus amp that uses a set of 530s. From all the research I have done on the amp, it seems that it is pretty stable and reliable as long as we don't exceed 50 watts. Might work great for a steady 40 watts on the V3.
Joel
N6ALT
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Re: strange behaviour of IRF MOSFETs
Whow about real RF transistors?
Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton - J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com
email:??bill@... ?
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On Nov 18, 2023, at 10:45 AM, Joel Caulkins/N6ALT <caulktel@...> wrote:
?Farhan,
I know you have always preferred the IRF510s, but have you considered the IRF530s? I have noticed that most of the cheap Chinese Linear amps use them to get a good 45-50 watts. I just bought a Micro 50 Plus amp that uses a set of 530s. From all the research I have done on the amp, it seems that it is pretty stable and reliable as long as we don't exceed 50 watts. Might work great for a steady 40 watts on the V3.
Joel
N6ALT
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Re: strange behaviour of IRF MOSFETs
Most prominently exhibited by those poorly designed amplifiers that do not account for thermal effects to bias related voltages. ?
Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton - J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com
email:??bill@... ?
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On Nov 18, 2023, at 12:36 PM, ajparent1/kb1gmx <kb1gmx@...> wrote:
?Farhan,
You didn't specify where or details.? This is the revised sBitx or some proto?
What the bias when cold and after immediately after a keydown session?
While my amps do not exhibit this, I've seen it in others especially when??
heating is an issue.? ?
Examples are the usual Ebay "70" watt amps?and similar copies.
--
Allison
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Please use the forum, offline and private will go to bit bucket.
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Re: strange behaviour of IRF MOSFETs
After I modified the output stage circuit at SBitx v2, I only now had the opportunity to test it in reality. There were several reasons for this, I didn't have a usable antenna, which is important. After switching to v3, I tried the device on the air for the first time. I replaced the AlN insulators when it was first discussed here on the forum. I also used a very small amount of Arctic Sliver 5 additive on both sides of the ceramic insulator. This is the weakest link in the heat conduction used here. I find that in long-term FT8 use, the heatsink on the back is approx. 40 degrees, then the current consumption decreases compared to the start. So the regulation takes place so that the output power decreases slightly (according to the instrument, about 1W). I use the device from 12.5V with a current limit of 6.00 Amps. I replaced the IRFZ24Ns once. Since this is from early production, it ran for some reason during setup. The point is that so far I am satisfied with the heat conduction, I have made about 50 connections with the freshly made top-fed delta loop antenna. I scaled it to 7MHz and it has good parameters at 7-14-21 MHz. I would like to thank Ashar for his persistent work. The design is well developed for visual and usability reasons. I didn't take a picture for this topic, but you can find them in another topic. -- Gyula HA3HZ
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Re: Beware of counterfeits 2N2219As
Because they are not lead (Pb) free, lead free one are about $2.34 US.
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Re: Beware of counterfeits 2N2219As
No chuckle here.... I ran into that building guitar pedals. The ic's I bought were labeled MN3007 which are kinda hard to get and expensive. But they?
ended up being a MN3207 which does pretty much the same job, but has a different pin out. That was a real head scratcher for me considering i'm not?
a real genius with electronics to start with.
73's
Dave K0DLP
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Re: strange behaviour of IRF MOSFETs
Ashhar thanks for all that experimentation!!!!
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On Nov 18, 2023, at 21:43, Owen Baldwin <owenbaldwin@...> wrote:
? Ashhar, can I first of all congratulate you on all the work on the sbitx V2 and V3. This new V3 I have upgraded to is superb and has gone well above all my expectations. It must surely has made the project more appealing to the new and old enthusiasts.
Farhan;
I switched out the silpads in my DE for Alumina Ceramic insulators. The attached thermal image photos show the stock silpad under the right FET and an Alumina Ceramic insulator under the left FET. The transmitter was key-down at 30 Watts for maybe 5 seconds. I saw a pretty dramatic difference between the two. I had planned to take some better images, as well as make a short movie showing the temperature difference resulting from an insulator change-out, but the FET on the right was having no more of it and shorted out.
No doubt that Aluminum Nitride insulators would work even better. I was able to get a lifetime supply of Alumina Ceramic insulators from Amazon in two days for not a lot of $$, so I'm happy with this solution.
My conclusion is that there is room for improvement from the stock silpads.
I posted a video in the files section a couple months ago - it shows that the FETs stabilize in temperature relatively quickly.
73; Steve, N3SB
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Re: Beware of counterfeits 2N2219As
Why are they so costly? The 2N2219s are about 9 dollars on Mouser. - f
Some of you guys may get a chuckle from this, but I tried swapping some of these into my uBitx and never really got them to work. Didn't think too much of it and moved on.?
I'm working on some circuits and I'm trying to do a test to see where they saturate out. The meter I have on the base goes backwards, so I'm like what's going on here. Stuck one on the checker. Then I stuck the rest on the checker. They're PNP! Last I checked the datasheet says that 2N2219s aren't PNP.?
These are SGS Thompson marked, 2N2219A H1223.
Guess I should stick to the NTEs I was buying.
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Beware of counterfeits 2N2219As
Some of you guys may get a chuckle from this, but I tried swapping some of these into my uBitx and never really got them to work. Didn't think too much of it and moved on.?
I'm working on some circuits and I'm trying to do a test to see where they saturate out. The meter I have on the base goes backwards, so I'm like what's going on here. Stuck one on the checker. Then I stuck the rest on the checker. They're PNP! Last I checked the datasheet says that 2N2219s aren't PNP.?
These are SGS Thompson marked, 2N2219A H1223.
Guess I should stick to the NTEs I was buying.
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Re: FT8 problem solution ...??? sBITX V2
Upgrade to V3. It sorts all these problems. - f
On Thu, Nov 2, 2023 at 4:00?PM Jens < hb9joi@...> wrote: I have the same big problem with the FT8 transmit-receive-time-slot management from the FT8 software .
Anybody knows a solutions how the FT8 program-code must be edited / new programmed that FT8 will work correct ???
Thanks in advance ... ! Jens / HB9JOI
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Re: v3 software, alpha is here
Thanks. ?This is what I was looking for.?
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Bob AA4FJ
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HA3HZ
K9HZ