I build a lot of electronic modules in my life, just from scratch, or from a existing design, from paper, etc. But sometimes I don't have the time or the fun to source all the parts. So buy kits. I built a lot of kits in my life too, but the last few years I had and still have a lot of fun with kits from QRP Labs.

The reason for me is that the kits are very well documented, not too difficult to assemble,  and,.....they work very well too.

 

QCX 5W CW transceiver

The first one was the QCX 5W transceiver for CW. I picked the 20m version.  If your take your time this kit can be assembled in a day or two if you are experienced in soldering electronics. Otherwise it will be quite a challenge.

I checked and double checked all the soldering and finally I put 12V on it. The kit was working as a receiver and all buttons and dials worked as expected. Read the manual and go through all the settings. It is a load of functionality. I put the CW speed to 20 wpm, connected my inverted V mono band antenna to the kit and started to listen. No problem at all to pick a bunch of stations. Than I started to test the output of the transmitter, and it was NO 5W by far. 0.5 W at best. So I had to find the reason for that. What could it be, the power amplifier is only three FETs, a coil to the plus 12V and a filter. I first checked the filter. It appeared to be cutting of the 20m signal to low, so at 14MHz most of the power was filtered and was transferred into heat in the FETs. OK, that explained the poor output. With my scope on the drains of the FETs I experimented with different filter windings and it was getting better a bit. Also experimenting with the coil to the +12V did not give a significant improvement. At the end I had about a Watt with 12V.

Not spectacular, but better. Increasing the voltage was working very effective. Putting 13V on the kit gave me 1.5W. 14Volts and the power went up to a little above 2.2W, 15V gave me 3.6W and 16V was good for,.......5Watt.

But,......the FETs were so hot that it started to smell and the power was going down again. Cooling helps but 16Volts is not a good operating Voltage for the long term. So I use the kit now at 12V for CW operation, and I also use the kit for WSPR-beacon. I put the voltage on 9V and work with 400mW. Excellent for WSPR I would say.

I have the kit now for more then a year and it still is doing a good job. This summer, if Corona permits, I want to take the kit to the outside with a vertical mono band antenna for 20M and start calling CQ on CW,.....

 

 

 

I wanted to get more experience with a little bit more power so I build the

 

QRP Labs 50W amplifier kit.

Here are my findings:

- fine kit, good price performance

- excellent documentation !

- Nice alu box

- it really supports QSK, the switching with the pin diodes works fine, although I used some bigger diodes for the switching. And you also need good capacitors to avoid to much heat at the output stage.

- So I like it for a good experiment, but,.....

What I don't like is the used transistor (IRF510). Yes it is cheap, but they are very intolerant for mismatches. I used during my experiments a whole bunch of it,....!

- The needed Voltage (20-24V) for the 50W is not really practical in the field, two batteries ??

End conclusion: nice kit for experimenting, but not very practical in use.

Detailed report of much more experiments:  Here

 

Ultimate3/3S QRSS/WSPR

Here are my findings:

- fine kit, good price performance

- excellent documentation !

- Nice alu box

- I build the whole kit in a few evenings. The winding of the coils of the filters was the most work and the only error I made was not soldering one of the coils 100%.

But after the fix of this error the kit worked 100%. I used the filters for 80-40-30-20-15-10.

It cost me quite some time to figure out all the modes, and all the options that are possible. My main purpose for the kit is WSPR. So I concentrated on this mode. I had to read the chapter about the timing of the messages and the framing a few times before I fully understood how to work with it.

- What I most like about the whole kit is that it is perfect also for stability experiments of the output frequency.

Well, For WHISPER my feeling is that it is not stable enough. But I also got the GPS receiver, so I connected that to the unit, along with the unheated synthesizer. The correction mechanism by using the GPS receiver works fine. But if the time between calibrations is to long (>10-20 minutes), the stability  is not within the 1 Herz. I wanted to know what I could reach in terms of stability, so I ordered the heated synthesizer of QRP Labs. Kind of tricky to get this together, but I you work slow and easy, it is very well to do.

And I love the Argo tool. It is really helpful in calibrating the frequency.

Some remarks about the experiments:

- my unheated synthesizers Cristal was oscillating a few kHz below the 27.000.000. But the Cristal of the heated oscillator was doing 27.002.120 ! So during calibration I was confused. It took me a while to find out that this was the fact. By heating up the oven in the synthesizer, I got it down a few 100's of Herz.

After finding the lowest freq of the synthesizers Cristal in the heated oven, the freq was rock solid stable within 1 Hz.

- Spectrum

The output of the transmitter after the filters gave a good sinus signal, but there were a lot signals around the main freq. When I did 14.097.150 (20m band whisper freq) I also got 14.097.050. It was 32dB lower. But is was there and some others too. So the output is not very clean, so to say. But in practice it will not be very disturbing. If you transmit with 1W of power, the 'extra' signals you transmit will be 1mW or less. If you are received in WSJT-X with +10, there will be possibly a 'shadow' with -20 !

Anyway, no showstopper to use the kit in real life.

 

My test set up was looking like this:

A PC with WSJT-X running. Connected to my FT-950 set with CAT, which was tuned to 14.095.600 Hz.

The transmitter kit, in the WSPR mode doing 14.97.150 every 4 minutes, also every 4 minutes the kit was calibrating itself against the GPS receiver.

On the PC I also had ARGO V1 build 145 running, to see the actual WSPR signal.

The output of the transmitter was attenuated 40dB and the rest was going into a dummy load. The antenna of my FT-950 (tuned dipole) was picking up enough signal from the transmitter to give me a WSPR +15 (and a shadow of -17).

 

Here some photographs:

 

The transmitter and the GPS

 

The FT-950 tuned at 14.095.600 Hz

The waterfall of WSJT-X. The hill in the horizontal line is the response of the FT-950 filter (400Hz). The high peak is the main signal  on 150. You can clearly see the "extras" you get every 100Hz !. However -32dB. The left "extra" is the 14.097050 Hz signal.