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5W mini transmitter for presetting the ATU
To all HF specialists:
I use the inexpensive and good ATU100 automatic antenna tuner.
Works well and is very inexpensive, I have already built several.
The transceiver whistles with about 5 watts or a short continuous tone.
Now the QMX has this very good and fast protection circuit. This means that setting the ATU is no longer possible.
Sure, I can briefly connect another transceiver to the ATU, but that's too inconvenient for me.
I want a small device with a frequency display that produces a 5W RF signal at the push of a button to quickly tune the ATU.
Would that work with that:
Si5351A synthesizer module kit +
5W HF PA?
Kind regards, Axel
DL5GT |
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On Wed, Jan 17, 2024 at 07:12 AM, Colin Kaminski wrote:
You could defeat the SWR measurement in the QMX.? Hello Colin,
thanks for your reply.
I don't want to bypass the SWR measurement, it's the safety shutdown of the QMX transmitter at bad SWR.
Before Hans implemented the SWR protection, I could usually get the ATU_100 to tune with the QMX. I have a 2 x 27m dipole which is not extremely bad on any of the bands.
The new SWR protection has already saved my QMX power amplifier once because I had accidentally transmitted without dummy load.
Depending on the band and frequency, however, this SWR protection does not allow me to transmit the necessary 4-5 watts for approx. 2-3 seconds through the ATU-100.
?
I would now like to have a small box, like the QMX, which sends a 5 W signal with a 9V block or a small 3S Lipo at the push of a button until the ATU has set itself up.
I know, in principle this is the QMX. However, if I deactivate the SWR protection, I risk damaging the transistors.
Also, I don't have 5 watts everywhere.?
?
Greetings, Axel
DL5GT
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Translated with DeepL.com (free version) |
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Hello.?
You can reprogram the atu-100 so that it will tune from 1w input.? There are lots of instructions on the Web for how to do it.? In the protection menu you can then adjust the tune % to output so that you transmit about 1w. On 40m mine I have to set for 55%. Then run the swr tune function in the hardware test menu that will trigger the atu.? You will still have the safety of the swr protection but can also use the tuner. Alternatively you could make an swr bridge that would sit between the qmx and the tuner.? you switch it in before transmitting. This would show a continuous low swr to the tx while allowing the full 5w to pass through to trigger the tuner.? The same as you would fine on the input of a manual tuner with an led.? I have not tried this method but I'm sure that would work also.? Sam? 2E1OCT? |
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Hi Axel,
I am also using the ATU-100 and modified for a QRP use. For the antenna tuning purpose I use a QMX?at reduced output power?with the 50W QCX PA connected. All supplied at +12V. This way both the QMX and the PA are operating at a safe margin whereas the ATU has enough input power to do the job. Works fine. However, it is not a very user friendly method to do.? As I am using just a fixed antenna I then remember the ATU settings per band and then use a demo mode to manually set the ATU when in QRP mode. Again, not very user friendly and not applicable for outdoor use. -- 73 Bojan S53DZ |
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Hello Samantha and Bojan,
?
thanks for your tips.
Switching the ATU to 1W seems to be a good solution. However, I don't have a programmer, and a good 30€ for a PICKIT 3, well...
Samantha, thanks for your tips on the QMX functions.
I have to admit that I hadn't looked very closely at the protection menu and hard maintenance test menu. |
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Sam, et al,
An SWR bridge will protect the transmitter, but it will NOT pass the full 5 W through to the ATU. Probably closer to half that. If the ATU truly needs 5 W, then this trick won't work.? -- 73, Dan? NM3A There are moments when everything turns out right .... Don't let them alarm you; they pass.? -Jules Renard |
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Besides being amused by the hard way approach, some thoughts.
The test transmitter has to put out the needed power on all bands of interest.? ?Easier said than done for many. I has to be robust, you are going to expose it to terrible SWR while the atu100 tunes. Or course if it fails, your back up plan?? More important when in the field. It must be efficient if portable as its using your field power. IT should have switching to remove it out of line or you do a lot of cable swapping. I'd suggest small. Me I use a Zmatch with a bridge sensor and also power meter. -- Allison ------------------ Post online only,? direct email will go to a bit bucket. |
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Good morning,
Yes, you have to somehow push the required power into the ATU-100 so that it rattles properly and quickly. A small transmitter with digital frequency setting would be ideal, regardless of whether there is a 2 x 27m dipole or an end fed for 20m attached, which sends the transmission signal to the ATU with 5 watts for 1-3 seconds. I will probably change the ATU so that it gets by with around 1W. In principle, it takes a bit of effort for me to pay €35 for a PICKit 3 programmer when the ATU-100 kit only cost €28. Can't you do the reprogramming without a programmer, e.g. with an Arduino uno, or Raspberry 4, or PC? Greetings everyone, DL5GT |
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On Thu, Jan 18, 2024 at 06:39 AM, Axel Kohlgrueber wrote:
Good morning,I just see that the currently delivered ATU-100 with program version 3.2 has already been changed to 1 watt input power for tuning. |
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Oh dear Oh dear, you should always look closely!
I'm currently assembling the fourth ATU-100. I ordered the first three about 2 years ago, they still required 5 W for control and, according to the construction instructions, each had 10 secondary turns in the tandem match transformer. Then in July 2023 I ordered two more ATU-100 kits. They already have them changed minimum power for tuning start: 1 watt Unfortunately, I wound the Tandemmatch Transformer according to the old building instructions with 10 turns each instead of 5 each. Damn. But it's also good that I noticed it. So I'll change the transformer and everything should be fine. Or can I save myself that? |
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Oh wow,
Now I have seen that all three ATU-100 tuners have the operating software set
to 3.2 when they were purchased. How can I now check whether the corresponding changes to the minimum input power
for tuning from 5W to 1W have actually been made? Do I definitely need this PicKit 3 programmer to read the hex file?
?
Do I have to reduce the 10 secondary windings on the tandem match transformer
to 5 windings each, or could it work like that? ?
Jeez... |
¿ªÔÆÌåÓýHi Alison,I used to use a Z-matches and they were good but FRI-match (PA0FRI) with printed toroids is much better! Wheatstone LED swr indicator very simple and effective. I do not even bother with a power meter, just check V and I on small metered buck. Of course I use silver plated wire-wrap wire and can get 5200 spots from hotel window in Vienna over 3 days. 73 Ross EX0AA On 18 Jan 2024, at 06:16, Axel Kohlgrueber <axelkohlgrueber@...> wrote:
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Colin Kaminski
Barb WB2CBA
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