-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of jerry-KF6VB
Sent: Monday, September 11, 2023 10:02 AM
To: [email protected]
Subject: Re: [SoftwareControlledHamRadio] T41 QSE carrier balance

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On 2023-09-10 21:14, K9HZ wrote:

> There is more to it.? Its not naturally balanced the way it is

> designed.

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*** What are the issues?? I was reading about the Tayloe detector this morning.

Apparently, it's not a mixer at all - rather a sort of commutated capacitor filter.

I remember reading about those in an article in 73 magazine back in IIRC the 70's or 80's.

I was fascinated by them - they were so simple - and easy to understand.

??I think I actually

built one.? It’s a lot of things but it is a mixer too if you read he original paper.? I think I have it if you want it.

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?? At first, I thought about the gains of U1 and U2, but that's probably not it;? the amplitudes of the incoming baseband IQ signals are adjustable via software.? Such adjustment nulls the opposite sideband, but has no effect on the carrier.? They are but that’s not what you want to do.? You lose dynamic signal range at the A/D and D/A when you don’t use them at full input (range). ?So you really don’t want to make that adjustment in software.

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?? So that leaves the RF side: U4, the dual D flipflop.? Delays in its flipflopperie?? I wonder if I could tack a small variable capacitor on each output?? There is some difference between flip-flops but not enough to make much of a difference in signal resolution.? The thing to do is get rid of them.? The real issue is the input trigger point.? Ideally, they should be balanced at the Vsg center point and a Schmitt trigger used to gate them…. But we never do this in practice maybe to our demise.

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?? I see that Hans Summer doesn't use a flipflop in the QCX+.? Rather, he just uses two outputs from an si5351a.? And he's not trying to transmit with it.? He gets the transmit carrier from the third si5351a output.? Yeah.? Why use them when you can perform very accurate quadrature IN THE si5351 from 1-110 MHz? !!!!!? You can even push or pull the quadrature angle a little if you need it.? MAGIC! (hint… you can even still drive the flip flops… use their output RF switched into the Tayloe and get VLF transceiver out if it!? WOW eh?? 250KHz to 100MHz transceive! Who wudda thunk?).

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?? I know that this has all been discussed in the past, and I apologize for rehashing it.? I'm just trying to get useful output from my T41.? You have no idea!

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??????????????????? - Jerry, KF6VB

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* I_N V12 WE HAVE MANAGED TO REDUCE THE CARRIER AMPLITUDE ON SSB TO
ALMOST -47DB BELOW A SINE SIGNAL AT FULL AMPLITUDE. THIS WAS
ACCOMPLISHED USING 3.3K OHM SERIES RESISTORS IN THE IQ CLK0 AND CLK1
FEEDS TO THE EXCITE MULTIPLEXER_.

This from Al's latest post- maybe worth a try. I am only getting
-20ish carrier suppression below full output amplitude with my V11
QSE.

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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

Am 09.09.2023 um 15:40 schrieb Larry Acklin <acklin@...>:

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Yes, all grounds are tied together in the V11 board.?

Audio routing of grounds generally want to stay away from chassis ground (old terminology) to avoid the noise and potential for leakage problems.?

In my experience in stage and live audio, ground loops are pretty common. DI (direct injection) interfaces are used to plug keyboards and acoustic guitars into PAs. They all have a “ground lift” switch that isolates the PA mic ground from the instrument ground. Hum is eliminated that way if needed.?

I’m applying the same method here. The schematic for V11 is correct with regards to the mic gnd and connection to the input and output jacks. The etch ties mic gnd to “chassis “. I’m now wired so mic gnd ties to sleeve on the jacks and the Teensy is the only return of mic gnd to common chassis ground.?

This is a star ground topology, specifically called for by the sgdt5000 codec chip used on the audio adapter.?

My result is no interference and decent quality audio in SSB.?

I’m sure that the compressor and EQ bugs can be found and squashed.?

Larry

KB3CUF?

On Sat, Sep 9, 2023 at 1:36 AM K9HZ <bill@...> wrote:

Huh… so all grounds tied together?? I wudda thought that DC and audio grounds were separate but tied together by a cap.? Anyway that’s what I’ve always done and it seems to work.

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Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

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Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

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Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

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Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

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email:? bill@...

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From: [email protected] <[email protected]> On Behalf Of Larry Acklin
Sent: Friday, September 8, 2023 10:57 PM
To: [email protected]
Subject: Re: [SoftwareControlledHamRadio] T41 Transmitting (noise in ssb) solved kinda

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Hi- I was able to Mcgyver something together and now I’m getting passable SSB audio. The mic gnd on the audio hat is now the ground return for the line out l,r and mic in. PTT also grounds through the same point. With mic gain at 0 setting, I can hear myself through a SDRPlay attached with about 70 db attenuation.?

There is a decaying echo with the audio- One (one one one) with about a second between echos, 3 or 4 as it fades edit: this was my listening to a speaker on the PC with SDRUino. Earbuds are not echoing It seems that any change in power settings requires the xmit EQ to be set up again- it reverts to -12 on all bands. Is this expected? I have been saving to EEPROM every time I mess with mic gain or output power. /End edit. . Above gain 10, things get wonky.I suspect??the mic comp code and xmit eq for both symptoms. So returning the mic and line grounds to mic gnd on the hat fixed the noise with no mic input but mic gain turned up. -20 db carrier supression -:/

Larry
KB3CUF

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Hi- I was able to Mcgyver something together and now I’m getting passable SSB audio. The mic gnd on the audio hat is now the ground return for the line out l,r and mic in. PTT also grounds through the same point. With mic gain at 0 setting, I can hear myself through a SDRPlay attached with about 70 db attenuation.?

There is a decaying echo with the audio- One (one one one) with about a second between echos, 3 or 4 as it fades edit: this was my listening to a speaker on the PC with SDRUino. Earbuds are not echoing It seems that any change in power settings requires the xmit EQ to be set up again- it reverts to -12 on all bands. Is this expected? I have been saving to EEPROM every time I mess with mic gain or output power. /End edit. . Above gain 10, things get wonky.I suspect??the mic comp code and xmit eq for both symptoms. So returning the mic and line grounds to mic gnd on the hat fixed the noise with no mic input but mic gain turned up. -20 db carrier supression -:/

Larry
KB3CUF

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73
Alain