|
Hi Everyone,
I have begun evaluating the 20W RF power amp by K9HZ (Dr. Bill Schmidt) with T41 to address the increased T41 V12 frequency and CW capabilities. Some of what I have found is as follows:
Frequency Response
A Bode plot of the amp stand-alone is shown in the first figure below. The response at both 5W and 15W (RMS) is essentially flat from 1MHz to over 50MHz. This covers the 6M band that the original T41 amp could not reach.
Power Output
Note that Bill (K9Z) rates the amp at 20W PEP, but it is current limited to about 16W (RMS). I tested the amp with two equal amplitude 7MHz tones but1KHz apart in frequency. at 16W RMS. The PEP of that is well over 20W and a scope plot of the LP filtered PA output (through a 50-ohm attenuator), showing the clean out, is contained in the next figure. A rating of 20W PEP represents a real-world SSB condition, since we rarely transmit sine waves on SSB, but rather complex speech waveforms.
I have used the amp quite a bit over the past week, and it performed flawlessly. No overheating at full power for extended periods on the 3.5"x1.5"x1.25" heatsink, with no fan. No thermal run-away. Also, because of the included current limiting, it is not possible to drive the output stage transistors to destruction. Since each final RD16H MOSFET is rated at 16W max dissipation, the amp is conservatively designed.
For anyone concerned about?less tha20W output, note that the difference between 16W and 20W is about 1dB, or 1/6 of an S unit on the receiver - not much at all.
SSB Signal quality?
That is currently under test and will be reported in the near future (waiting on some hardware components).
CW signal quality
As contrasted with SSB signals, CW is always a single tone, which is limited to 16W RMS (for sine waves 16W RMS is equivalent to16W PEP).
The first CW plot is a narrow band spectrum of a 7.2Mz CW tone from the T41 V12 into the K9HZ amp. The plot is centered on 7.2MHZ with a 20KHz span. Within that bandwidth the signal is almost 80dB above the noise, with no other spurious components. The next plot is a wide band spectrum from?3Mz to 30MH?of the 16W 7.2MHz amp output, through the T41 LP filter. The second harmonic is at -51.5dB relative to the 7.2MHz fundamental, well below the -43dB limit.
Efficiency
The amp draws about 620mA with no signal and 2.46A at 16W, indicating a class AB mode with about 45% efficiency at full power.?
For reference, a typical 300WH portable 12V battery would provide well over 15 hours of SSB operation with the T41 and K9HZ amp.
Bottom line
Jack and I fully recommend the K9HZ 20W amp for use with T41, especially for those wishing to have an extended frequency response to 6M, with V12 T41 boards.
For readers of the T41 book, please note that we plan to include this material and more regarding V12 performance in a revision of the book to be added in the near future. These additions are reflective of changes suggested by builders of the T41. Afterall, the T41 was designed to be an experimenter's platform and that is exactly what has happened, both in hardware and software innovations. Thanks to all who contributed.
For those who already have the book, we will post the additional material to this site in the files section at the same time the book revisions are completed and uploaded.
K9HZ 20W power amp Frequency response
K9Hz amp output at 16 W with Two-Tone input
Narrow-band spectrum T41 CW mode at 16W
Wide- band spectrum CW output at 16W
|
Thanks Al… ? With the expanded frequency range of the T41 RF board (QSE+QSD),? I suspect this little PA will be right at home.? So far, I’ve sold over 800 of them and I will need to re-order components for further semi-kits.? I’m also thinking about partnering with a couple of people what want to make them (eg. Finished PAs) for those hams who want to build them but just don’t have the time/ patients/ ability/ etc.? That way we all win. ? The 100W PA module is next.? It has the same basic frequency specs as the 10W PA but is 100W RMS (110W PEP)… and with the attenuator board, you can precisely dial your power from just a few milliwatts to 100W in half-dB steps.? All of it integrates into the T41 directly/ perfectly. ? More on this when I return from vacation next week (some vacation… I’m replacing wood floors.? UG!). ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ?
toggle quoted message
Show quoted text
From: [email protected] < [email protected]> On Behalf Of Albert Peter Sent: Saturday, September 9, 2023 10:01 AM To: [email protected]Subject: [SoftwareControlledHamRadio] More T41 V12 Results ? Hi Everyone,
I have begun evaluating the 20W RF power amp by K9HZ (Dr. Bill Schmidt) with T41 to address the increased T41 V12 frequency and CW capabilities. Some of what I have found is as follows:
Frequency Response
A Bode plot of the amp stand-alone is shown in the first figure below. The response at both 5W and 15W (RMS) is essentially flat from 1MHz to over 50MHz. This covers the 6M band that the original T41 amp could not reach.
Power Output
Note that Bill (K9Z) rates the amp at 20W PEP, but it is current limited to about 16W (RMS). I tested the amp with two equal amplitude 7MHz tones but1KHz apart in frequency. at 16W RMS. The PEP of that is well over 20W and a scope plot of the LP filtered PA output (through a 50-ohm attenuator), showing the clean out, is contained in the next figure. A rating of 20W PEP represents a real-world SSB condition, since we rarely transmit sine waves on SSB, but rather complex speech waveforms.
I have used the amp quite a bit over the past week, and it performed flawlessly. No overheating at full power for extended periods on the 3.5"x1.5"x1.25" heatsink, with no fan. No thermal run-away. Also, because of the included current limiting, it is not possible to drive the output stage transistors to destruction. Since each final RD16H MOSFET is rated at 16W max dissipation, the amp is conservatively designed.
For anyone concerned about?less tha20W output, note that the difference between 16W and 20W is about 1dB, or 1/6 of an S unit on the receiver - not much at all.
SSB Signal quality?
That is currently under test and will be reported in the near future (waiting on some hardware components).
CW signal quality
As contrasted with SSB signals, CW is always a single tone, which is limited to 16W RMS (for sine waves 16W RMS is equivalent to16W PEP).
The first CW plot is a narrow band spectrum of a 7.2Mz CW tone from the T41 V12 into the K9HZ amp. The plot is centered on 7.2MHZ with a 20KHz span. Within that bandwidth the signal is almost 80dB above the noise, with no other spurious components. The next plot is a wide band spectrum from?3Mz to 30MH?of the 16W 7.2MHz amp output, through the T41 LP filter. The second harmonic is at -51.5dB relative to the 7.2MHz fundamental, well below the -43dB limit.
Efficiency
The amp draws about 620mA with no signal and 2.46A at 16W, indicating a class AB mode with about 45% efficiency at full power.? For reference, a typical 300WH portable 12V battery would provide well over 15 hours of SSB operation with the T41 and K9HZ amp.
Bottom line
Jack and I fully recommend the K9HZ 20W amp for use with T41, especially for those wishing to have an extended frequency response to 6M, with V12 T41 boards.
For readers of the T41 book, please note that we plan to include this material and more regarding V12 performance in a revision of the book to be added in the near future. These additions are reflective of changes suggested by builders of the T41. Afterall, the T41 was designed to be an experimenter's platform and that is exactly what has happened, both in hardware and software innovations. Thanks to all who contributed.
For those who already have the book, we will post the additional material to this site in the files section at the same time the book revisions are completed and uploaded.
K9HZ 20W power amp Frequency response
K9Hz amp output at 16 W with Two-Tone input
Narrow-band spectrum T41 CW mode at 16W
Wide- band spectrum CW output at 16W
|
Al
I'm getting quite confused with the? accolades you are awarding to the new V12 boards.? They seems to be amazing.
Where can I see the schematics for all the V12 boards?? It's probably staring me in the face but I can't find it.
Thanks?
Harry GM3RVL
|
Files section of this forum… ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ?
toggle quoted message
Show quoted text
From: [email protected] < [email protected]> On Behalf Of Harry Brash Sent: Monday, September 11, 2023 12:49 PM To: [email protected]Subject: Re: [SoftwareControlledHamRadio] More T41 V12 Results ? Al
I'm getting quite confused with the? accolades you are awarding to the new V12 boards.? They seems to be amazing.
Where can I see the schematics for all the V12 boards?? It's probably staring me in the face but I can't find it.
Thanks?
Harry GM3RVL
|
|
|
i can't find it ----i'm using linux? do I look thru all 9 pages of files?
|
Open the web page for the group. On the top right click updated twice. That will result in a latest post sort.? 
|
On Sat, Sep 9, 2023 at 10:01 AM, Albert Peter wrote:
Note that Bill (K9Z) rates the amp at 20W PEP, but it is current limited to about 16W (RMS).
What limits the current in this amplifier? Something on Bill's amp board or within the rest of the T41?
?
-Nate?
N8BTR?
|
The amp itself (actually the first gain stage) is the limitation.? That was done on purpose to make the amp bullet proof (short or open the output to the antenna and things are just fine).? You CAN drive the final stage harder by increasing the feedback resistors on the OPA device.? I was more interested in longevity.? ? When you sell kits that for amateur builders, the fastest way to lose the builders focus is to design the PA (or any other part of the radio) so that its not robust to inadvertent mis-operating.? The uBITx and the sBITx falls into that category.? The final transistors on those radios pop like popcorn… Farhan when through several cycles of redesign to keep his PA transistors intact when the operator mis-stepped.? A lot of people were mad over that and their radios went up on the shelf after the first or second incident.? I don’t design stuff like that. ? I design stuff so that the poor kid in the Caribbean that can barely afford antenna wire much less parts for his new radio if it blows up… doesn’t experience a failure that puts his radio in the closet.? It’s easy to do… its just that very few people do it because they want every Last watt out.? Truth is, my 20W PA is capable of about 45 watts… and will even operate class A (if you really want a very linear signal from it… just by boosting the bias).? But all of this reduces the safe operating margin.? So I under-rate and under-run the amp and keep everyone happy. ? ? Dr. William J. Schmidt - K9HZ J62K(J68HZ) 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> On Behalf Of Nate Reik N8BTR via groups.io
Sent: Friday, April 25, 2025 2:33 PM
To: [email protected]
Subject: Re: [SoftwareControlledHamRadio] More T41 V12 Results? On Sat, Sep 9, 2023 at 10:01 AM, Albert Peter wrote: Note that Bill (K9Z) rates the amp at 20W PEP, but it is current limited to about 16W (RMS).
What limits the current in this amplifier? Something on Bill's amp board or within the rest of the T41?
|
Oh BTW the 20W drives the 100W module to 110W with 8W. ?So its overkill for the 100W PA.?
Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton - J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com
email:??bill@... ?
toggle quoted message
Show quoted text
On Apr 25, 2025, at 11:06?PM, K9HZ <bill@...> wrote:
? The amp itself (actually the first gain stage) is the limitation.? That was done on purpose to make the amp bullet proof (short or open the output to the antenna and things are just fine).? You CAN drive the final stage harder by increasing the feedback resistors on the OPA device.? I was more interested in longevity.? ? When you sell kits that for amateur builders, the fastest way to lose the builders focus is to design the PA (or any other part of the radio) so that its not robust to inadvertent mis-operating.? The uBITx and the sBITx falls into that category.? The final transistors on those radios pop like popcorn… Farhan when through several cycles of redesign to keep his PA transistors intact when the operator mis-stepped.? A lot of people were mad over that and their radios went up on the shelf after the first or second incident.? I don’t design stuff like that. ? I design stuff so that the poor kid in the Caribbean that can barely afford antenna wire much less parts for his new radio if it blows up… doesn’t experience a failure that puts his radio in the closet.? It’s easy to do… its just that very few people do it because they want every Last watt out.? Truth is, my 20W PA is capable of about 45 watts… and will even operate class A (if you really want a very linear signal from it… just by boosting the bias).? But all of this reduces the safe operating margin.? So I under-rate and under-run the amp and keep everyone happy. ? ? Dr. William J. Schmidt - K9HZ J62K(J68HZ) 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? ? On Sat, Sep 9, 2023 at 10:01 AM, Albert Peter wrote: Note that Bill (K9Z) rates the amp at 20W PEP, but it is current limited to about 16W (RMS).
What limits the current in this amplifier? Something on Bill's amp board or within the rest of the T41?
|
Bill,?
? ? I think this makes a lot of sense to design this way when others are building and operating! I appreciate you commenting, good to know that was the mindset in your design. I've been trying to learn more about HF amplifier design, so I may ask more questions as I build mine, but understanding that I'm....at my own risk for any deviations I choose to make!
?
-Nate
N8BTR
|
OF course. ? ? Dr. William J. Schmidt - K9HZ J62K(J68HZ) 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> On Behalf Of Nate Reik N8BTR via groups.io
Sent: Sunday, April 27, 2025 9:33 PM
To: [email protected]
Subject: Re: [SoftwareControlledHamRadio] More T41 V12 Results? ? ? I think this makes a lot of sense to design this way when others are building and operating! I appreciate you commenting, good to know that was the mindset in your design. I've been trying to learn more about HF amplifier design, so I may ask more questions as I build mine, but understanding that I'm....at my own risk for any deviations I choose to make!
|
K9HZ