Oops...sorry. My experience was with U3S and the question was about the QCX. But I think they use the same processor, so the same TCXO solution should work for the timing. But my comment about losing

Hi all, I described in detail a non-GPS solution for keeping WSPR on time in a series of posts here last year. The thread title is TCXO for U3S CPU clock Summarily, one would install a TCXO with ampli

Next: Agreed, BS170 won't work at 2m. You should be able to get some signal at 144 MHz out of a BSN20-7 MOSFET or others. But driving it with the QCX's 74ACT00 might not work. I've inserted a similar

#mods #vhf #qcx #chat

Hi Rob, That's a clever alternative to a digital pot. It would use about the same amount of space in the EEPROM, less code in the firmware, and no need for a digital potentiometer in the circuit. If I

#u3s

Hi Rob My adapter for the surface mount MOSFETs is below, on the right edge of the image. The middle terminal is the drain; this is the pin through which most of the heat goes. It solders to a larger

#u3s

Namaste, Sarma, Thank you for filling in the context! I read a bit about how the usdx works. It seems that it updates the clock generator according to the audio signal and then modulates the RF output

#u3s

Namaste, Sarma, I don't know what a "usdx" is... or a "qo100". Sorry! Halden VE7UTS

#u3s

Hi Rob 1. I'm using one BSN20-7 MOSFET. It's a SMD-only part. I mounted it to a PCB "adapter" to give it a large copper area on the drain to dissipate heat. I also used this scheme with one BS170 on 2

#u3s

Hi Rob, My U3S is set up with a 10V brick power supply regulated down to 8.4V. The 8.4V charges a pair of Li-po cells. Diodes enable the unit to stay powered when either power source isn't there. A li

#u3s

Hi Cierra, The ones at this link are QCX not QCX+, but there are a lot of style examples. My really like the one at the bottom of the page. https://qrp-labs.com/qcx/qcxgallery.html -Halden VE7UTS

#enclosure #case #qcxp40

I used the FOX TCXO at first. Its frequency jumps made WSPR unreadable on the higher bands. It is fine for some of the other modes and probably works even on WSPR for the lower bands. The Taitien (sea

#u3s

Hi Mike FYI, there is a perhaps-rare application where the Fox TCXO won't work very well. This TCXO adjusts its frequency in small jumps. For CW and while on the HF bands, these jumps are usually too

My QCX runs on 4 Li-ion 18650 cells from Tenergy. This turned out to be more capacity than I need for a few hours of operation. For even lower mass, my QCX-mini will run on 4 Li-ion 14500 (AA size + a

Some success! I found a simpler way to boost the U3S’ output on 6m, and it helped even more on 2m. I installed a BSN20-7 MOSFET in place of the BS170. I chose this transistor for its lower input capac

#u3s

Hi Dave, My QCX suffered a similar incident. Alex removed the bad chips for me and left just enough solder on the pads that I was able to tack new chips on. It's hard to see the individual pins on the

Hi Hans, Thanks for your explanation of the design reasoning, especially the basis of the "ACT" in the TTL numbers I know so well from my high school days. Your comment about the need for 5V drive to

#problem

Greetings QRP Labs fans, I’m using only one BS170 and ~8 volts in my U3S’s PA and am getting about 0.2W output on 6m. I’d like to raise that. The Si5351a’s output impedance spec is 50 ohms, which matc

#u3s

Hi Ian Another, much more complicated approach, is to wire up a TCXO to run the MCU's clock and also rig up battery power so the unit will run for a while when the power goes out. Details about the TC

Hi Hans I built my QCX with sockets for those opamps so I could swap them for other types to save power. But I never did. I can't find OPA2272 on the internet. Is it the same as TLC2272? Cheers Halden

Another update: First, a brief summary. Details are in prior posts here: I wish to run WSPR on my U3S (firmware 3.12a) for long periods and without a GPS DO to keep it on time. I installed a TCXO in p

#u3s #clock