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Hi Dan, thanks for the note.

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Well… Switching a tuner in and out basis SWR is a very easy thing to do.? The real problem is the tuning.? If the SWR is 5:1 (and you are not using one of my indestructible 20W or 100W PA retrofits for your QRP radio)…. you will always risk the chance of blowing up your PA in the tune phase.? You can also get into “hunting” issues if you are on the edge of the tuner trigger (say at 2:1… where the SWR bounces between 2.01:1 and 1.98:1 with the antenna movement in the wind).? I’m also not a fan of “Hunt-and-peck” tuner algorithms that all of the hobbyists tend to use. ?Using the direct transform method seems way more appropriate so that the initial guess would be? right in the vicinity of where the actual tune solution actually is and may save your PA when tuning under full power.?? Another way to do this is to tune under reduced power… where you give tune into a resistive load and just use a small sample of the power from that load to determine the tune parameters.?? Of course the real way is to back the power down on the PA to a place where it won’t matter.

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I do have a tuner on the drawing board that I build for te uBITx that uses a lot of this… has a signal at tune initiation that tells the radio to go to low power (that could mean switch to a resistive load with a very lower power tap for tuning), uses phase and magnitude info to determine the transform from the radio to the antenna… and then solves for the inverse transform (read that tuner parameters) to present a 50 ohm load to the radio from the transform solved for the proper structure, L, and C values all within a few milliseconds.

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This project works well for all of the QRP radios I’ve worked with and is in the queue to get designed for board sales.? I have a few projects in front of it… like six… so it will be a while.? The T41 is just about finished… the 100W module is almost ready to be put up for sale as a kit. (the 20W module is available right now).

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Sorry there is only one of me.

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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

?

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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Bill,
?I posted this to the QRP Labs reflector:

"There have been quite a few posts about ATUs and possible damage to QCX, QDX, and QMX finals. So it seems that someone should design and market a QRP ATU that has a resistive/absorptive bridge built-in which is automatically switched in every time it is triggered. And the bridge would only be switched out if the resulting VSWR is below 2.0 (or whatever programmed value you want.) and it should be the same size and run from the same voltages as those rigs."

So there is one other consideration for a lot of QRP rigs. That is to protect the finals when tuning. Yes, protection could be integrated into the radio, but why not have a tuner that protects the radio?

Any thoughts?
--
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Dan
NM3A at mail dot com

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Bill,
?I posted this to the QRP Labs reflector:

"There have been quite a few posts about ATUs and possible damage to QCX, QDX, and QMX finals. So it seems that someone should design and market a QRP ATU that has a resistive/absorptive bridge built-in which is automatically switched in every time it is triggered. And the bridge would only be switched out if the resulting VSWR is below 2.0 (or whatever programmed value you want.) and it should be the same size and run from the same voltages as those rigs."

So there is one other consideration for a lot of QRP rigs. That is to protect the finals when tuning. Yes, protection could be integrated into the radio, but why not have a tuner that protects the radio?

Any thoughts?
--
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Dan
NM3A at mail dot com

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Well not so fast.? Just because you use a transformer doesn’t change physics… Here that transformer just widens the transform space in the real direction.? You still need to change the structure to generate the right transform if the impedance is too low…? See below:

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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@...

?

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A couple of things about the two-step tuner... The innovation in the Palstar patents appears to be the use of a transformer (unun) on the transmitter side, so matches are made to 450 ohms. The patents claim this allows the use of just one L-network topology for all antenna impedances. Another, reversible transformer on the antenna side broadens the impedance range of the tuner.

The AD8302 looks like a very useful IC, and a good alternative to phase detector designs like the mixers in the NanoVNA. The only drawback is, it costs $22 in quantity one.

73,

Wes AC8JF

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A couple of things about the two-step tuner... The innovation in the Palstar patents appears to be the use of a transformer (unun) on the transmitter side, so matches are made to 450 ohms. The patents claim this allows the use of just one L-network topology for all antenna impedances. Another, reversible transformer on the antenna side broadens the impedance range of the tuner.

The AD8302 looks like a very useful IC, and a good alternative to phase detector designs like the mixers in the NanoVNA. The only drawback is, it costs $22 in quantity one.

73,

Wes AC8JF

On Nov 9, 2023, at 22:58, K9HZ <bill@...> wrote:

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Well… yes.?

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I have a slew of tools that I usually use on antennas before I comment particularly when I do it for contract work.? I have not done that here so I guess I have no further comment other than if it works for you.? Great.

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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@...

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From: [email protected] <[email protected]> On Behalf Of Gordon Gibby
Sent: Thursday, November 9, 2023 9:25 PM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] FW: [Elecraft] HI CUR warning on K3

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Hi, Bill, something got lost in the translation.

- The antenna is not nonresonant
- The antenna is not end fed
- The issue being discussed was I thought off-center fed dipoles & common mode current
- The reason the antenna is relevant is that it is a 160 m off center fed dipole (OCF) & therefore works on a slew of bands above that ; The point being that we have experienced no difficulties with common mode current with our extensive digital operations

what you might not know is that this goes through an extremely densely treed forest and it took hours and hours and hours of work nearly to get a single straight section of wire through. Many many slingshot efforts in dense ?underbrush. ?Trying to put up a loop or any other more complicated antenna is unreasonably difficult in that physical setting , and with increase the chance of us losing the antenna in a hurricane, the very system for which we are trying to provide back up communications. This was the best we could do because the radiated nearfield noise from electrical equipment within the building was 30 or more dB stronger so we had to move to the woods. ?

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Hi, Bill, something got lost in the translation.

- The antenna is not nonresonant
- The antenna is not end fed
- The issue being discussed was I thought off-center fed dipoles & common mode current
- The reason the antenna is relevant is that it is a 160 m off center fed dipole (OCF) & therefore works on a slew of bands above that ; The point being that we have experienced no difficulties with common mode current with our extensive digital operations

what you might not know is that this goes through an extremely densely treed forest and it took hours and hours and hours of work nearly to get a single straight section of wire through. Many many slingshot efforts in dense ?underbrush. ?Trying to put up a loop or any other more complicated antenna is unreasonably difficult in that physical setting , and with increase the chance of us losing the antenna in a hurricane, the very system for which we are trying to provide back up communications. This was the best we could do because the radiated nearfield noise from electrical equipment within the building was 30 or more dB stronger so we had to move to the woods. ?

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It is going well. By my counting I get 10 1/2 loops before I run out of room in the center. I have not quite finished for 2 reasons,
1. I read your notes, recently got a teensy and display and have been trying to understand how to make that work. I have some of the software pieces set but haven't got all the referenced libraries down loaded yet.
2. To test your unit I need more test equipment. With xmas coming budget is a bit strained and I need to wait to buy some of the equipment. In particular a TinySA Ultra which acts as a signal generator. I have a lot to learn so I am taking step by step.
I appreciate all the assistance that you have offered.
I am also waiting for v012 boards to be published. I need them and a few of the others.
I am certainly as knowledgeable as most of the others in this group but I enjoy the learning and building aspect the most.
73, Bruce

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Here's a typical example I was attempting to describe:?

Consider that the Z at the input end of a 50 ft section of Zo=600 ohm line is 227+j521.? Assume that's the measured S11 value from a single-port antenna analyzer module.? Transmission line software like TLW can mathematically find precise component values that convert the complex Z into 50+j0.? In this case, I selected a high-pass L network option.? The resulting component values are 43 pF series C and 5.36 uH shunt L at the line side.? No fuzzy logic needed to ignorantly step relays until a VSWR value under 1.5:1 is achieved.? By joining an S11 analyzer with the transmission line software into one unit: (1) the mag + phase is measured; (2) component values are computed; and (3) the analyzer module switches L and C components to those values in one switching event, perhaps through an I2C interface.? ?Images below.

Paul, W9AC

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I have the original first edition of the book published in 1987. I guess that makes me an OM now.

FYI, Palstar got a couple of patents on this concept in 2019-2020 (you can patent a ham sandwich) and was shopping it around to companies that manufacturer tuners.




Maybe their intent was to license the technology, but I suspect it was to set up a future patent infringement suit should someone independently develop a tuner using this approach and sell it. The clue was that the only representative from Palstar in the room was their lawyer. There is a big difference in patent litigation between accidentally and knowingly violating a patent. When their lawyer made the rounds, he was likely looking to eliminate any chance that a company could argue they were unaware of the patent. Ham radio companies are not generally run by savvy business people and the people in the room I was in did not understand his intent.

The concept has obviously been around for a while and is a solution that anyone skilled in the art could come up with. I don't bring this up as an issue anyone developing one for hobby use should be concerned about. Just an interesting anecdote on the subject.

73,
Scott
AK5SD

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Hi Bill,

are you familiar with this QEX article? After I read it, I found a ton of information about using mixers as phase detectors:



de Karl Heinz - K5KHK