Barb,

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built your pocket tuner. Neat little kit! Put it in heat shrink, and cut out the LEDs / buttons. Tunes my EFRW 16m long with 9:1 balun from 15m to 60m for the mid-band QMX. Just needs getting used to, as the tuning is not as smooth and steady as a Z-match - the discontinuities are quite remarkable. For me what works well is tuning under field conditions at home with a Nano VNA, noting the values, and then using same set up when portable. The two LEDs give a quick and useful feedback on the road. Thank you for sharing! A have a few boards left over, which I would be happy to mail to anyone interested, within Switzerland. Contact info on QRZ.

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Peter HB9EBE

Dear QDX, QCX and QMX users!

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I'm writing in this thread again because the ATU described below is in the final stage of development and has been specifically designed as a great complement to QRP Labs transceivers, which provided a completely new class of portability. The answer to this is the size of the proposed ATU: the KT-005 has 49% of the volume of QRP Labs transceivers.?

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Take a look at what ATU looks like in practice:

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Preliminary KT-005 User Manual for the assembled version:

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73!
Krzysztof SQ5IXA

This looks great!? what are your plans for price and availability and will it be a kit?

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73

Peter GM0EUL

I noticed that the tuner only matches up to 3:1 mismatches. A radio like the QMX will commonly be used in the field where you may not have an antenna that is between 16 and 150 ohms such as end feds or matching an antenna designed for one band on another, etc. The Elecraft T1 matches 10:1 mismatches and is much more useful for the purpose.?

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A tuner board without case that will handle 10:1 and could be mounted and integrated inside the QMX+ would be a popular device, I think.?

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Just suggestions...

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73, Kevin K3OX

Please correct me If I'm wrong sir, but shouldn't that large mismatch be tuned at antenna's feed point rather than at trx's side?

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On Mon, Sep 9, 2024 at 10:50 AM, sp9paz wrote:

shouldn't that large mismatch be tuned at antenna's feed point rather than at trx's side?

In the field, that might, be practically the same point.??

73, Don N2VGU

As Don N2VGU said. But even if the feed point is somewhat separated, while ideally the tuner would be at the feed point, it's good to at least be able to match it to the radio somewhere. The short coax feeds usually used in the field (when they are used) tend to mitigate the downside of this.?

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Bottom line, 3:1 tuners are not that useful (in my view) seeing as how most radios will work into 2:1 mismatches without a tuner.

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73, Kevin K3OX

hi

ATU-10 a QRP automatic antenna tuner developed by N7DDC who developed ATU-100
tests:

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Dear All,

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thank you for your warm comments and emails. I have read them all carefully and will answer them.

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1. I have to admit that about 70% of the interest comes from the US, so yes. I have to make ATU available in the States somehow.

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2. Thanks for the suggestion that it would be good to make a similar ATU that could be mounted inside the QMX+. I admit, I did not realise this possibility. I will try to propose something on this topic. It would be a single-board circuit that would fit the existing pins in QMX+ I think.

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3. Attenuator topic. As you can see in the datasheet (check the PCBs layout) there is absolutely no free space inside to add another relay. Maybe a simple switch is an option, but I am afraid of this solution. If you forget to turn it on while tuning you can fry the power stage. I will measure on the QCX-mini 20 m version, how much power you can set with ATU without without exceeding 60 V voltage on BS170 transistors. Of course I already have ideas in my head for the next version of this ATU with some improvements (PRO version?), but I can't do everything at once.

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4. I have placed the proposed prices on my website. Yes, kit version with populated SMT components on PCBs for self assembly is in my roadmap. Hopefully, a few preseries units (soldered manually) will be available by the end of October. The next batch (assembled on the SMT machine) will be available in November.

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5. Thanks for your valuable comment regarding the matching range. I have initially defined the tuning range as 15...150 R (3:1), although a wider range is of course available for this topology and selected components. Due to high miniaturization, the actual PCB layout was designed with a 16 mils spacing in power path. At 10:1 we can expect voltages up to 70 Vpeak inside ATU, but it is still enough for good insulation between traces. The relays also have sufficient margin to carry currents up to 1 A at the specific conditions (e.g. C shunt branch @ Z = 10 + j50). All capacitors are at least 200 V rated. I will update matching range once all testing is complete: frequency vs load conditions at nominal power.

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73!

Krzysztof SQ5IXA

The little Chinese Z match antenna tuners are about the right size. Work well. You will need a banana jack to BNC male adapter for field attachment of a wire antenna. Also the 1:9 un-un might be necessary. UHF to binding posts, so a jumper cable there. I replaced the wing nuts on the un-un with real binding posts. I have banana plugs on all of the ends of my field antenna wires for quick connections, FWIIW. Not as pretty, but the 4SQRP "T" tuner works well. Then, there is the ATU-10. I am uncomfortable with the transients when it tunes. Might be rough on the finals. I go for the manual tuner most of the time. The ATU-10 works very well at the home QTH with my Xiegu G106, 1:4 un-un, and about 35' of wire in the back yard run to a plant hook from the eves. I am on the ground floor. Good ground rod as well for the other side of the 1:4 un-un.

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Excellent Krzysztof! Sounds like you will have a winning product! I am thinking of a board for my QMX+. Poor persons KX2 anyone?

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On Tue, Sep 10, 2024 at 09:32 AM, Paul Ross wrote:

I am uncomfortable with the transients when it tunes.

I use my QRP-O-METER between my QRP Labs radios and my ATU-10; set to VSWR is places an absorptive bridge inline, which limits the VSWR the radio sees to less than 2:1.

It seems to tune OK despite the 6dB lower signal into the tuner.

73, Don N2VGU

I use Elecraft T1.

- Bill? W3WJ

On Sat, Jul 27, 2024 at 08:04 AM, Peter HB9EBE wrote:

Barb,

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built your pocket tuner. Neat little kit! Put it in heat shrink, and cut out the LEDs / buttons. Tunes my EFRW 16m long with 9:1 balun from 15m to 60m for the mid-band QMX. Just needs getting used to, as the tuning is not as smooth and steady as a Z-match - the discontinuities are quite remarkable. For me what works well is tuning under field conditions at home with a Nano VNA, noting the values, and then using same set up when portable. The two LEDs give a quick and useful feedback on the road. Thank you for sharing! A have a few boards left over, which I would be happy to mail to anyone interested, within Switzerland. Contact info on QRZ.

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Peter HB9EBE

Peter,

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Check my github for update on pocket tuner. These updates improves tuning for a smoother tune process. No change on pcb. Just swapping capacitors and changing 51 ohm resistors to 47 ohms.

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Thanks Barb, already made the adjustment by swapping the caps and reducing the resistors to 47 and now it works really well! Haven't had the time yet to measure efficiency, but the small and lightweight form factor makes it a nifty little tuner for hiking!

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73 Peter

HB9EBE