开云体育

Dear all,

On most class C and D amplifiers the IRF510 is followed by a trifilar or bifilar transformer toroid.? ?Can someone please explain what the function of the this type of transformer is.? (is it for impedance matching?) Google is just not providing me with a easy understandable answer.? ?

73
Timo
zr6tm

PAGE LAST UPDATED: 20-Jan-2023

Thanks/73,

I was thinking about the physics and hassle of removing enamel from the wire we use for toroids, and suddenly this came to me. It works GREAT for me on the larger diameter wires, +/- 24/26 guage. It is especially useful on those short wires we sometimes have to work with.
Grind off the seam zipper posts, leaving them as very short guides for the wire, sharpen the central knife surface, and scrape away. Laying the wire on a finger and moving the tool, at a slight angle, usually works best for me. Of course you will need to rotate the wire to get all surfaces cleaned.
73, happy scraping,
Bruce K3BAB?

Old school frequency spectrum analysis for 40m but very cool if you see this pic Hans:



Ed Tink

Hello everyone!
I'm THRILLED to report that my QDX is back up and running after being QRT for 16 days! ?Replacing the 4 BS170 MOSFETs and the IC5 driver fixed it!

What have I learned or done this month especially in the last 16 days?

• There are a great group of patient people on this board willing to share tips, practical knowledge, encouragement and words of wisdom!
• QDX cannot tolerate high SWR even for "short" periods of time,
• Researched impedance matching units (commonly called antenna matching units) automatic vs. manual tuners,
• Learned why a manual antenna tuner with a 50 ohm resistive bridge is really necessary vs. automatic antenna tuners which often present high VSWR while chasing 1:1. (I am now using the recommended EMTECH ZM-2.),
• Located the QDX troubleshooting information on Hans' website and found it helpful,
• Learned how to tweak my QDX power output by adjusting the windings on L2, L3, L4, L6, L8 and L10. (done)
• Better understanding of the QDX design after reading through the comphrensive design notes in the manual,
• Understand how to update the firmware (done),
• Understand how to get into QDX terminal applications mode and review information (done),
• Upgraded/replaced my almost 40 year old Weller TC201/202 soldering iron to a variable temperature controlled Hot Air Rework and soldering station,
• Learned surface mount component rework techniques (paste, ideal temperatures, types of solder, tricks, etc.) and
• Upgraded/replaced my coax jumper cables (between QDX, pwr/swr meter and ZM-2) with high quality cables and connectors to mitigate potential intermittent connections.

With the 4 BS170's and IC5 replaced, I now see 4.7 watts on 80m, 4.9 watts on 40m, 4.1 watts on 30m and 4.8 watts on 20m! ?(9 volts input)

When I obtained IC5 from Hans, I also ordered the parts (less the case) for another QDX (80-20m version). ?Since I didn't use it, at some point, I'll order another case and the QDX high band components to get me on the higher bands. ?I may wait a while in case Hans tweaks the high band specific components with the additional feedback and ongoing experimentation.

I also have the 40m QCX+ (and companion 50 watt amplifier) kits here awaiting my attention. ?For now, my day job continues. ?All in good time!?

I would like to thank N1JBJ, NM3A, VA3SYS, K8WPE, N2VGU, N6OTQ, "Mark", AE5ZA, VK3ELH, DJ4DI, KF4AYT and OH2AWG! I sincerely apologize if I neglected to mention someone! You have all been super helpful! ?Also, thanks to Hans for designing, documenting and distributing such great and affordable kits!

Ciao! and 73, ?Peter W1DAD ? Windham NH

开云体育

The biggest issue you are facing is that with a kit almost anything could be wrong. ?Excessive gain suggests the wrong resistors were put in the feedback loop on an OPAmp, so grab a magnifying glass, put the board under a bright light and check all the values. ?I am an experienced builder and I have made that mistake! ?The symptom was that the phasing adjustments didn’t work!

I seem to have killed my QCX+ receiver. It still receives but very very low sensitivity.
I may have overloaded the front end here in the shack by keying another radio nearby or it got damaged connecting to a Signalink USB interface. I suspect I overloaded the front end.

Im not sure where to start troubleshooting. There are several low voltages throughout the system starting with T1. Due to? the number of checks, I will attach a pdf showing them all.

I tried to factory rest and realign. The alignment was not possible due to low signals into that section. The oscillator worked but I could tell by the graphs and numbers that something was not getting into these sections loud enough.

Any help would be graciously appreciated. I do not have a scope but fairly proficient with all the other tools needed.
Kind thanks in advance.

--
regards,
Bryan, N0LUF

Hi folks,

I'm a relatively new amateur and this is my first build: a 40m QCX-mini. When we tried to do the adjustment and alignment, the gain only had to be turned up to maybe 1 on a scale of 1-10 to reach a volume level of 9, as suggested. However, none of the trimmers seemed functional (R27, R17 or R24). My guess is the two issues are interrelated, but where this is my first build, I wanted to ask the group, as someone has probably experienced this in the past.

Thanks in advance!
--
Thanks and 73,

Tim

VE1XR
Fort Ellis, NS, Canada

Try changing the double click duration. Mine was to short to work.

开云体育

Still looking for some help with this one,

According to the OpMan v1.08/1.09 the backlight can be temporary controlled by Double Clicking the rotary encoder shaft button (page 33 section 7.11)

On the web page qcxmini/firmware under version 1.07a - Moved backlight control to triple-click of left button

My QCX Mini is version 1.09a and I cannot get either of these to change the current state of the back light.

The backlight can be switch on/off via menu 7.11

So software feature or operator feature?

73,

Warren vk3byd

Finally completed my U3S kit and ready to put it online.

Modified the design for two antennas: VHF (2m independent on the main board) and HF (10, 20, 40, 80 and 160m on the relay switched LPF board).

I went for 3 BS170s and added a fixed 5V regulator for the board and variable one up to 12.4V for the PA all from a single 13.8V supply. I have the PA set to 8V for now and the output power levels for all bands look good.

The left switch on the front turns the LCD display back light on/off. Just missing a grommet for the GPS antenna cable.





Cheers,

Ed Tink
VA3EJT

I did get the software that Bruce, K1FFX, produce and is available here: /g/QRPLabs/message/93506?? It does work much better than my hack.? I did find that the Armbian OS for my Orange PI 4 did not do a complete Python3 installation.? To run the software, I had to install pip and other tools(wheel, etc).? Run the two Python3 scripts will tell you which Python modules are missing.? You then install the needed modules with pip.? The software works nicely.? One only has to run the script with python3 qdx_ui_105.py?? The script is good for check the time signal stations, CHU and WWV.?? Thanks to Bruce for information on his software.
?

Thanks Dave - that's the reassurance that I needed. I still have some hardware debug to do, I'll post what I find.

73,
Steve - NU7B

Hi Willie:

For the uncorrected pressure I'm also getting zeros, so this seems to be a communication issue. In looking over what Adafruit offers, I noticed that their module using the MPRLS sensor, has the correction applied internally, so that saves using math with variables that the U4B does not directly support (perhaps there is a programming workaround for signed 32 and 64 bit integer).

I'll order one of those sensors, but there's still some debug to do on the MS5607 - I'll take a look at the signal lines with a scope. This sensor is made in Switzerland and ordered from Mouser, so shouldn't be a source problem. I also may have uncovered a compiler bug which I'll write Hans separately about.

73,

Steve - NU7B