Assembly Pre-game
After building a couple QMX and QMX+ radios, I figure I have a couple of informed thoughts on the build process for anyone thinking about purchasing a kit or preparing to assemble theirs.Back when the QCX was all the rage, I posted this page with some info on the toroids. I figure this is somewhat along the same lines as that.
When I build a QMX kit, the first thing I do is take a simple inventory of the parts. The QMX typically includes the same PCB boards which need to be split up and sanded as described in the assembly manual.
Next, I get the bag of capacitors and toroids which are band specific, depending on which version of the kit purchased: 80-20m, 60-15m, or 20-10m. The remainder of the kit is the same for all versions.
It is helpful to have a completely clear workspace to assemble the kit. There are a lot of small parts that need to be organized (and stay organized). A few tips for organizers I've found helpful:
Capacitors
Usually I use a jeweler's loupe, magnifying glass (Dollar Tree again), or even the camera on my phone to see the small writing on each of the kit's dozen different values of tiny ceramic capacitors.
To use your camera, adjust the zoom to be able to get in close and see the writing. You'll have to adjust the distance to get it right - and figure out which camera lens is being used! For my most recent build, I used my son's digital microscope. It actually worked really well once I got the focus adjusted! (Although I would not go so far as to recommend buying it just for this use - it's not exactly ideal, but it worked well. They are fun to play with regardless, so catch them when they're on sale.
Once you can easily read the values on the capacitors, I grab a fine tip felt pen and write the value shown on the label on the small cardboard tab each capacitor is still taped to. For example, if the capacitor has the value 221 written on it, that's what I write on the cardboard.
Once I've done that for each of the capacirots, I go back and reference the manual (or you can look below) and write down the associated component identifier. So, that "221" would be C402 on the 80-20m version; or C402/C516 on the 60-15m version; or C515 on the 20-10m version.
Here are the values for each of the 3 versions available at the time of writing:
80-20m Version
| 60-15m Version
| 20-10m Version
|
Once all the capacitors are labeled, it's time to get the toroids inventoried.
Toroids
A couple years ago I was headed out on a work trip and knew I would have plenty of downtime on the plane, so I bought some small plastic bags. I put the cores into their own individual bags, labeling each bag with the kit part number, the number of turns that toroid should have, and the length of wire specified in the manual (recreated for you below). I put all the small bags into a larger ZipLoc bag and was able to get that portion of the build done while on my trip. It doesn't take hours to do, but it helped me pass the time.
Doing it this way helps keeps all the parts organized and, at least for me, helped reduce any part mix-ups or confusion.
A couple of winding tasks are not so easily done on-the-go. Specifically, I'm referring to the binocular cores. I save those for when I'm firmly at home - and the trifilar transformer. Consult the manual, but I put all this info here so you have it all on one screen for easy reference if you're, like me, choosing the small plastic bag route.
What I discovered from that is how much easier it make construction to do all the winding before getting out the soldering iron. Putting the completed wound toroids back in their labeled bag helps assembly go more smoothly.
80-20m Version
|
60-15m Version
|
20-10m Version
|
With those ready, the other toroids you'll need to wind are:
80-20m Version
|
60-15m Version
|
20-10m Version
|
| Part Number | Core | Turns | Length |
|---|---|---|---|
| T401 | Dull black | 10T, trifilar (see manual) | 25cm × 3 twisted together ~60 times |
| T502 | Dull black | 10T | 22cm Use .60mm wire |
| T507 | Small binocular | 10T, each side plus two 1T (see manual) | 25cm × 2 |
| T501 | Large binocular | see PA transformer manual | 12V: 25cm and 20cm 9V: 24cm and 20cm |
So there you go, that's how I begin my QMX build. Once I have the parts organized, dive into the assembly manual and follow the steps.
I highly encourage builders to read the directions step by step first before beginning the build. Then re-read each step twice when installing each part. Because the parts are so densely packed, any mistakes takes much longer to correct than going slow in the first place.
Should you run out or need more wire, the wire in the kit is #28 awg enamel-coated magnet wire.
Be sure to check the final values of the toroids you've wound before soldering them in place.
I use a cheap LC meter I got off eBay long ago. There are also "transistor tester" kits you can build but many cheap multimeters can be found online that do inductance measurement.