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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

I put a jumper on the V12 Main board to add PTT to the microphone jack. I'm finding it handy.

ALL: Has anyone received a copy of the new T41 book? The new version supposedly became available after April 4th and has a black T41 on the cover and Appendix C on Calibration has been expanded to a new chapter (#20). If so, please let me know, as I have ordered review copies for Al and myself twice now, and they have sent the old pre-April 4th version. Thanks! Jack, W8TEE -- Jack, W8TEE

Finished building the LPF Control board, no detectable shorts or opens and no smoke escaped. The board is configured for I2C addressing and the address jumpers are set for address "25"(Open, Short, Open). However address LPF not found at 25, running SDT Ver66-9. I ran I2C Scan and an address of "28" is showing up on wire 2. How is that possible? -- 73 to you! 73 Bob W3RDL Virus-free.www.avast.com

Hi. I purchased a set of boards from Justin, AI6YM. I working on putting the RF module/board. Looking at the schematic, it reads that R35 and R37 are supposed to be 3.3KΩ. Looking at the board, which has all the SMT populated, I noticed the 3.3k Ω resistors have 0Ω soldered on top of them. Was this a mistake, or or should thy be 0Ω? R40 and R42 have the 0Ω resistors in place. Thank you for your time. Duane - K5CA

All: Greg pointed out that Amazon (finally) has changed the ad on their page for our updated DSP book: Note that the publication date is April 16, 2025. The bad news is that we lost over 150 reviews where most (85%) were 5 Star reviews. That will hurt as that's a good rating for a technical book. So, if you like the book, please take the time to write a review. If you don't like the book, go ahead and write a review...just don't send it in! Jack, W8TEE -- Jack, W8TEE

Al and I released an updated version of the book, but we didn't feel it was worth calling it a new edition. The problem is I've placed two different orders and was sent the wrong printing. That has been fixed now, even though the ad has an April 18, 2024 for the release. There are two obvious differences that you can use to tell if you're ordering the right edition. First, the T41 on the cover should be black, as shown below. Second, and more important, if you click on the Read Sample button below the book image and scroll down, you should see that it has A new chapter (Chapter 20 on Calibration). That chapter is new with the update and expands upon the information that was in Appendix C on earlier editions. Jack, W8TEE -- Jack, W8TEE

All: Recent there was a negative post about the V11 boards and the T41 from 4SQRP. I got this private email from Neville Marr, ZL2BNE, who has been following the T41 from its inception. He has a T41 from 4SQRP and speaks positively about it. I asked him if I could re-post his email because I know there are a lot of 4SQRP radios out there and he wants everyone to know that it is a good radio that he uses on a regular basis. I, too, have a 4SQRP T41 and it is a very good radio. He gave me his okay to post his email. Jack, W8TEE =============== Hi Jack, We haven’t communicated in quite some time but I continue to check-in on the softwarecontrolledhamradio group from time to time. I’ve recently reviewed postings and one took my attention … for the wrong reasons. /g/SoftwareControlledHamRadio/message/33358 The post was pretty disparaging of the V11 receiver performance, among other things calling it an intolerable toy radio. I see no point in giving such posts oxygen on the forum but I felt a need to let you know my experience is totally different. You will recall I was an early adopter of the T41 project, I had V10 boards made and did my own thing. You will also recall I was quite critical of some aspects of the project. I always had issues with the transmit side of my V10 T41 but never the receive side. The receiver worked from day one. In my case I don’t hear any noise on rx with a dummy load connected. I can easily hear my Marconi sig gen set as low as it will go at -127dBm. It’s a very good receiver. Over time I made a number of hardware changes to my QSE, I built two filters of my own design, one follows the QSE the other follows the PA. Final transmit change is adopting the K9HZ PA. Today my radio works faultlessly using Greg’s T41EEE. I got everything where I wanted and started logging contacts in August 2023. I’m not much of an operator but do put my creations on the air. I’ve just interrogated my log to discover I’ve logged exactly 100 contacts using my T41. Quite a cool number. I’ve had the T41 on the air more times than that, mainly local nets, but all the same 100 in the log. Below is a breakdown of the 100. I’ve worked every continent except Africia (Africia is notoriously difficult to work from NZ, South Africia is the rarest DX from NZ). So thank you for getting the T41 up and running. I am a little sad that V10/11 got supplanted by V12 because V10/11 is a very good radio. I do hope people can get V12 to a place where V12 T41 are on the air too. My T41 is my go-to radio, my daily runner. Cheers, Neville ZL2BNE -- Jack, W8TEE

For those of you in the UK/EU… Andy Rutter, G8HCK, has graciously agreed to distribute T41/ K9HZ/ K9HZ-KI3P boards and kits there. I’ll attempt to ship him a load of stuff and he will make arrangements to ship to you. In the short term, you should give him your order and at a time in the near future… he can forward the combined order for me to ship to him. You can contact him at: arutter@... 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: www.VillaGrandPiton.com Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. email: bill@...