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The short answer is the U3S needs to be powered. It is not powered from the Arduino. There's a doc at QRP Labs site covering updating a QCX, but the procedure works the same for U3S.

When using Avrdudess to update the firmware on my U3S, going through my arduino uno, does the arduino power the U3S or does it need to also be powered? Hope this ain't to stupid of a question. LOL.

Another question is how warm does the BS170 get during the 2 minute WSPR cycle? I tend to worry about them getting too hot if operating with high a duty cycle. I my situation my U3S is coupled with

Hi Vernon: I'm using my vertical Hustler 6B for the radio. It's the same antenna that I switch to for my normal HF operations. When I stop seeing reports on wsprnet.org they are gone until I replace

Al: I haven't checked during transmit, I'll try and do that tonight. I'm powering everything through a simple linear power supply. I might try isolating the power to the BS170s. When I checked the

Todd are you confident you dont have a intermittent issue with your connection to your antenna and antenna itself? Vernon Sent from my Samsung Galaxy smartphone.

That's an interesting problem. Have you checked the U3S' current draw through the power supply in both 'idle' and 'transmit?' That might give you an idea if for some reason the PA is drawing too much

Thanks, Hans.? I have built many kits over the years and your instructions are the best by far!? Love the QCX design, and looking forward to my first QSO when I get it completed. Al KD4EO

Greetings: I built the 3S about 6 months ago and when it works it works great (multiple contacts to DP0GVN with a vertical in Missouri). It will work for a week or so and then it fails. I replace the

Hi Al Yes. 73 Hans G0UPL http://qrp-labs.com >

I am just nearing completion of a 40M QCX kit with Rev 3 board.? I want to replace C21 and C22 with .1 mf caps.? Am I correct that the .1 mf caps are now ceramic disc caps, and NOT electrolytic caps

Hi Kurt Yes 73 Hans G0UPL http://qrp-labs.com >

Greetings all; OK so I understand the differences between Rev 3 & 4. Since my 20m version is Rev 2 & 40m version is Rev 3, can I make those changes reflected in Rev 4 to my Rev 2 & 3? 73; Kurt - W2MW

I am in the process of soldering my QCX, trying to keep solder bridges from forming, no smoke yet. But I noticed both of them should get 5v, and I wasnt sure if a solder bridge was ok or not. I will

Excellent. Thanks for confirmation. Got an excuse to fire up the soldering iron tonight :) Chris M0XTE Links: 1. /g/QRPLabs/message/25097 2.

Hi Chris In Rev 4 C21 and C22 are replaced by a smaller part footprint, for the 0.1uF (instead of 10uF). They were moved a bit to make space also for the optional C54. But there is no change to the

yes, I poked my 10 ?f out and replaced them with great improvement on the clicks Martin DK3UW

Hi, For the sake of clarity, I assume that the only change is the part footprint on the PCB and we should be retrofitting 100nF caps on rev 3 boards as well in the existing footprints? Chris M0XTE

Hi Sven, all Yes, Alan is correct - PCB Rev 4 is being supplied now in some cases... the only change is the replacement of C21 & C22 with 0.1uF capacitors (formerly 10uF) to reduce click on Tx/Rx

Hi Sven, The product home page https://www.qrp-labs.com/qcx.html has the "important" information of the differences in V4 revisions! Alan