QCX+ has arrived, building experience

 I DREAM

I need a new project. So how about... a QCX+ 5W CW transceiver?  And learning CW??? Or just doing WSPR TX to monitor my propagation???

A PACKAGE ARRIVES

So the package arrived, ahead of expected delivery time. 

Package in post

IN THE BOX?

I  opened it up. Wow. Impressive. Excellent quality of components. Beautiful panels. I will drill an extra hole in the back panel eventually to feed out the raw IQ Tayloe audio signals to an SDR program like HDSDR. (which I have running on WIndows 10 under Parallels on my Mac Mini). Connection will be via a USB soundcard plug-in dongle MIC input.

Contents!

What a pile of bits and pieces. I had not expected so many, nor such a complex PCB. This will take some time to assemble, even though I am a quite experienced builder...

GETTING READY TO WORK

My build station, with ELAD FDM-DUE SDR for FT8 contacts 

and Macbook for instructions

And now let's read the manual - twice!

THE DREADED COIL

The coil 39 + 5 + 5 + 5 turns

The coils took me hours. I tried the method in the instructions. But in the end I did it my way. First the 39 turns, marking off with a tally every 5 on a piece of paper. Then 1, 2 & 3 coils of 5 turns. Each set had its start and end wires twisted together. And after I  puzzled out which holes to thread them though. Finally, check, check again and solder. Hold the iron on for the full 10 seconds recommended to burn off the wire coating. Test for continuity, all OK.

Phew, have a long rest. No need to rush it. This will take days...

THE  PCB

Time to have a look round the PCB and mount some intitial pieces, start with the ICs

Coil and some ICs fitted

Onwards an upwards...

16 x "104" CAPACITORS

Scattered all over the board are 16 x "104" decoupling capacitors. These are next to install. 

A note: the capacitors come fix along a cardboard strip, just cut them off, there will be plenty of wire left for mounting, don't try to tear them off the mounting strip this will just bend the leads and leave glue on the leads.

16 x "104" capacitors installed

5 x "474" CAPACITORS

Now I mounted the 5 x "474" capacitors. The group close together at the top are the Tayloe detector filter capacitors to detect the IQ audio signals before the amplifiers.

5 x "474" capacitors

TAKE A BREAK - that's enough for now let's see if I can work some European FT8 non 40m... then carry on... 

Was it a mistake to empty out all the components? Lots of searching for the right ones!!!

Tipped everything in a box of chocolates lid!!!

RESISTORS

Most capacitors done, starting on the resistors. On these Chinese blue background resistors it is quite impossible to read the colour code - need to check every one with a meter. 

PROBLEM

Got to section 3.30, "Install 2 x 36K resistors R32 & R33". There were two "orange-blue- black-red-brown" in the kit but when checked with a meter they were actually 39k! LTSpice re-simulation of the CW filter does not change much with the 39k resistors.

LTSpice with 39k resistors on third filter stage

I have emailed QRP-Labs (Hans) with a query about this. Awaiting a reply. This is where I am at right now

Up to section 3.29 this is my build

Oh dear. I have found the batteries in my test meter were low, I have replaced them and now the 36k resistors read 36k. Have written to Hans to apologise.

Nearly made another resistor measurement goofy when checking the 750k resistor R35, it measured 560k until I realised I was measuring the resistance of my finger!!

WOW, that's all the resistors done. Here it is

Finished the main board resistors

OTHER COMPONENTS

Trimmer, electrolytics, transistors. Neat way the output power transistors are mounted and held down by a screw and washer, Very neat idea.

Output power transistors

Now for those wretched toroids. Two things will help. The first is the web site toroids.info. Here you will find the listed toroid core types T37-2 and T37-6 and for each the dimensions and more impportantly a way to calculate the inductance from the number of turns (or vice versa). And to the right length of the wire needed. This is great as you can cut a length of wire and not have to pull the whole length through each time, but just the shorter length you need. For example for L2 in the Low Pass Filter - 24 turns

T37-6 24 turns needs 35.6 cm of wire, cut 38 or so to be safe

And the second trick is to photo the coil when it is done, then zoom in to count the number of turns is correct...

Yep, its 24

So let's do all the coils 21, 24 and 21 turns

All the coils mounted

Next is the Antenna connector, a BNC type - though I would have referred an SMA to match all my other bits of gear.

FINISHED

Completed mainboard

NOW THE FRONT PANEL

Components mount on both sides of the front panel. First the front side resistors

Five front side resistors

Now the rest, back and front. Three wire have to be used to connect the volume control.

Front

Back

I used red, yellow and black wires for the volume control, thought it would look prettier.

The LCD is installed with mounting screw and nuts. One problem is that the righthand nut on the back cannot be fitted as it collides with the volume control, I temporarily loosened the volume control to get the nut on to have the correct spacing before soldering in the 16pin header. This remains a problem as it cannot be fitted again when the QCX+ is fitted in its enclosure.

Finished!!!

ALIGNMENT  & ENCLOSURE

I have aligned the radio, there are two things to adjust, the input tuned circuit to peak on the 40m CW end of the band and the detector IQ phasing & balance to reject the wrong sideband - CW RX reception is on USB at 700Hz below the displayed TX frequency.

I have also purchased the  excellent enclosure  for the radio, and here it is before I put the top on. I did have a queer problem. When I tightened the nut on the BNC connector it pulled the main board backwards it disconnected the front panel, and the screen went dark - bit of a shock, but all was well when I removed the nut and pushed the two boards back together.

Finished radio

Second problem was crackling when the boxed unit was "tapped". This turned out to be poor solder joint on one of the LPF coils. It IS important to solder then on for the full 10sec to burn off the wire coating!!! 

MORSE

Now the challenge begins, to learn morse code!!! First a paddle morse key? I am building this one.

3D printed paddle morse key