The mcHF RF board. The Toroid inductors have a big blob of hot glue melted into the center hole. The glue goes all the way down to the PCB keeping them in place. On the right the SWR/Power meter inductors have also a small dab of hot glue on the side. In the background the transformers also have some hot glue to keep them in place.

I also decided to tack down the inductors using some hot glue. I know it is getting warm inside so that might just create a huge mess, but it is worth a try. If that does not work out I will remove it and replace it with silicone. We will see™️ :D #hamradio #kitradio #mchf

The mcHF RF board with an SO-8 Temperature sensor soldered on. There is a copper tape shape bridging across from the SO-8 To the square oscillator package.

The same mcHF RF board but without the copper tape connecting the thermal sensor with the TCXO

The mcHF RF board before the temperature sensor was soldered in. The SO8 package is missing.

I got some silicone thermal pads for the TO-220s, so I have to take the radio apart and put them in. While I am at it I am also adding the optional TCXO temperature sensor. The instructions recommend to couple the oscillator and the sensor with some copper tape. #hamradio #kitradio #mchf

I have to wait for a dummy load and a few other bits and bobs to arrive before I can calibrate the radio and try to go on air with it. In the mean time I am trying to get familiar with the controls and while doing that I managed to receive some SSB on 40m! 🎉📻 #hamradio #kitradio #mchf

The mcHF QRP radio fully assembled in it’s enclosure.

And here we go! We have a fully assembled mcHF QRP radio! There is more work to do, but let's sit back and enjoy the view l for a little bit! :D #hamradio #kitradio #mchf

The front of the mcHF enclosure in the background. In the foreground there are scissors holding two silicone buttons in a strip.

The front panel has some silicone buttons. But oddly enough these are not mats that fit the hole pattern. One has to clip the buttons apart and then insert into the button holes. It makes the assembly a bit awkward because the buttons love to fly out of position. #hamradio #kitradio #mchf

Now the UI board can be mounted on top of that. Let's finally remove that pesky protective film from the LCD display! #hamradio #kitradio #mchf

The mcHF radio enclosure with the RF board installed. On top of the RF board is a piece of sheet metal with multiple cutouts for components. This is the RF shield to decrease the amount of interference from the UI board coupled into the RF board.

Next: the RF board, followed by an RF shield. The enclosure comes with an RF shield but it needs a bunch of modifications. So instead of doing that I designed my own RF shield and ordered it from Send Cut Send! It worked out great. You can find the design on my GitHub. ;) #hamradio #kitradio #mchf

Speaker screwed into the back half of the mcHF radio enclosure. The speaker has a red and black lead with a connector soldered to it.

First thing for the case is to screw in and solder the wire to the speaker. #hamradio #kitradio #mchf

The mcHF UI board with the R8 resistor soldered in. This provides phantom power to the electret microphone of the handset.

Remember how at the beginning we were missing a resistor for the electret microphone? It arrived, so let's solder it in before we assemble the whole radio into the enclosure. #hamradio #kitradio #mchf

The two Power Amplifier (PA) MOSFETs in TO-220 packages. There are screw nuts on the thermal pads that have a dab of solder in the corner keeping them in place. The components are already soldered into the RF PCB.

The two through hole voltage regulators. There are screw nuts on the thermal pads that have a dab of solder in the corner keeping them in place. The components are already soldered into the RF PCB.

The voltage regulators installed in the radio enclosure. Showing that it is a very tight space making the installation of the screw nuts difficult.

To install the TO-220 PA MOSFETs and LDOs it is necessary to partially assemble the RF board into the case. It is really hard to get the nuts onto the chassis bolts so I decided to solder them onto the tabs. (these are the moments I praise having a JBC iron!) #hamradio #kitradio #mchf

The mcHF RF board. Three white boxes which are the micro relays as well as a glass bulb with two electrodes inside. The bulb is a neon bulb connected to the antenna.

mcHF RF PCB back still visible are all the magnetics, but now it also has a relay mounted.

Full view of the front of the mcHF RF board. With the connectors, relays, neon bulb and the balun installed.

After mounting one stray relay on the back side of the board, we can finally assemble the parts that go onto the "front side" of the RF board. Another funky balun, 3 relays, some connectors and a neon bulb to protect from the antenna zapping us. :D ⚡️ #hamradio #kitradio #mchf

The mcHF RF board with a bunch of magnetics and the BNC connector mounted. The newly added items are two square cross section toroids with 10 enameled wire windings each. The toroids also have one winding of a coaxial cable each. The coax provides “Faraday shielding” to provide adequate reverse isolation for the transformer. I am pretty sure the bend radius on those coax wires is "illegal" and that the board was not originally designed with this topology in mind. I am pretty sure there are better ways to lay it out so that it is not so painful to install... :D

Last hand built items on the RF board are the SWR/PWR meter transformers. Installing those coax windings was a major pain in the back side. But the toroids are wound in opposite directions as the documentation describes, and things seem to be connected where they belong! 😅 #hamradio #kitradio #mchf

The mcHF RF pub with 12 toroidal inductors. The winding count varies from left to right. On the left the inductors have less windings than on the right. The left most set of three inductors are for the roughly 10m bands, then 20m and 30m. The last two columns are 40m and 80m bands.

Here we go! All the filter inductors are wound and soldered in! I tried my best to do an even and clean job... I did check them with the low cost LCR meter I have and they seem to be in the ballpark of the specified values. #hamradio #kitradio #mchf

The green mcHF RF PCB. In the center there are three red ferrite toroids with copper enameled wire wound around them. From left to right they have 24, 27 and 24 windings each.

Schematic of the mcHF filter circuit. There are four groups of filters. For 80m, 40m, 20/30m and 15/17/12/10m bands. Each group of filters is a series of three inductors with capacitors connected to ground between each stage.

Now I need to wind all the inductors for the lowpass filters. Each filter consists of 3 inductors. I started with the 80m band toroids. 24, 27 and 24 turns each. #hamradio #kitradio #mchf #kicad

The mcHF power amplifier section schematic as viewed in KiCanvas.

Sidequest: I took the mcHF design files and imported them to KiCad. You can find them on my GitHub. github.com/esden/mchf-kicad and yes they open in KiCanvas!!! ;) UI Board: kicanvas.org?github=https... RF Board: kicanvas.org?github=https... #hamradio #kitradio #mchf #kicad

The mcHF RF board with three hand wound devices using multi aperture ferrite cores. (each core looks like a binocular) From left to right. Power input choke, 2T bifilar transformer and TX 2T/3T transformer.

The mcHF RF board with one dual aperture ferrite core. This is the TX power amplifier input 4T/1T balun.

I have mounted the first few hand wound devices on the board. A balun, a choke and two transformers. They are part of the power amplifier circuit. (still getting the hang of hand winding and soldering these in…) #hamradio #kitradio #mchf

The mcHF board with the BNC, KEY, ACC, Power plugs soldered on. In the top middle of the board a small balun is also visible. The left lower corner is missing an SO-8 package that is meant for the temperature sensor.

Let's start on the RF board. Simple stuff first! Power jack, KEY and ACC, the BNC for the antenna, and an off the shelf balun. I still have to order the optional temperature sensor that would be added in this step to for some extra TCXO temperature compensation. #hamradio #kitradio #mchf

First power up of the mcHF UI board. The firmware that the kit came with is quite old. V2.5.106 and the bootloader says “Unknown”. But NO SMOKE so that is great news so far!

To power the board I used some jumper wires to connect the 5V supply to the board through pin 28 on the 30 pin connector. Then to force the board into the built in DFU bootloader I used a small grabber to short the P6 jumper. After the bootloader is updated we don’t need to use the jumper any more.

After updating the bootloader I was able to flash the newest firmware onto the board. It is V2.12.2 from 2021, I have the feeling the firmware development slowed down a bit. ;) The new firmware immediately feels snappier and the encoders work more reliably.

Now that the UI board is fully assembled we can test it! It is also time to update the boot-loader and firmware! All we need is some jumper wires and a USB cable. And the verdict is… NO SMOKE! (more details in picture ALT text) #hamradio #kitradio #mchf

A sandwich of screen, interposer connector and the UI PCB. At the end it is quite wasteful because it uses an off the shelf breakout providing the 2mm pitch connector strips but it costs a lot of height making removability of the LCD module a challenge.

The screw machine headers mounted directly onto the shortened pins of the interposer PCB. The removed pin header shrouds sitting next to the LCD module.

Screw machine headers soldered into the UI PCB.

The UI PCB with the LCD module mounted into the case showing that there is no gap between the case and the screen as well as no gap between the case halves and the screw holes align. (I know the screen protector is driving me crazy too! I will remove it when I do the final assembly of the radio)

Original design of the mcHF UI board has the LCD module soldered directly to the PCB. There is not much vertical space to allow for connectors. I decided to remove the pin header shrouds, cut the pins shorter and use screw machine terminals to make it removable. #hamradio #kitradio #mchf

Two LED soldered into the UI board. They are elevated above the board without dedicated standoffs. In production one would use plastic standoff sleeves to make the distance consistent. Doing it this way is too finicky otherwise.

The mcHF case mounted, showing the tips of the LEDs through the holes. The holes have quite a lot of tolerance around the LEDs.

Ok, they turned out all right. There is way more wiggle room in the case openings than I originally expected. I did not have to be so precise about it. 😅 #hamradio #kitradio #mchf

mcHF case shifted to the right, over the UI board. Holding a through hole LED with tweezers sitting against the edge of the case to gauge the distance to the PCB.

I decided to temporarily put the case and boards together. I want to make sure that the recommended standoff distance for the LEDs is what I want. #hamradio #kitradio #mchf

mcHF radio UI board with the encoders and tact switches soldered on.

Next I have added the encoders and the tact switches. Interestingly the pads for the SMD tact switches are genuinely massive, because of that, getting them soldered on centered and straight is much harder than it should be. :/ #hamradio #kitradio #mchf

The mcHF UI board with the inter board connector mounted. It is the pin header which is not how the original kit is designed but it is better because the RF board is providing power, and it is better to have sockets on the power side and pin headers on the side that receives power.

Just a chunky USB-A host connector next to a now ancient looking Mini-USB connector. We might need to do something to convert it to USB-C at some point in the future? :D

Now the UI to RF board interconnect and the USB-A host connector. This brings us to the massive list of suggested mods to the original build of the board. It recommends putting pin headers on the UI board and pin socket on the RF board. github.com/df8oe/UHSDR/... #hamradio #kitradio #mchf

Two green PCB with protective foam around the electrolytic capacitors. The top board is the User Interface (UI) board and the bottom one is the RF board that will be doing all the magical radio squiggly stuff. :D

This is what we are starting out with. The top board is the user interface board and the lower one is the RF board. I am following the instructions on GitHub for the steps. We will start putting the connectors onto the UI board first. github.com/df8oe/UHSDR/... #hamradio #qrp #kitradio

Two green PCB. Lower one is the user interface and the upper one is the RF board. In the right upper corner are little baggies full of parts. In the left upper corner is the enclosure. In the left lower corner is the display for the radio.

It has been sitting in a box on my shelf for way too long! It is time to finally assemble the mcHF radio! Let’s see how it goes! :) #opensource #hamradio #amateur #qrp #electronics #assembly #kitradio