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Tag: QRP Labs

QCX 30m Bamotech case and calibration

QCX 30m in Bamotech custom case

Another step nearer to using the latest addition in anger.

The PCB is now living in the custom built Bamotech case, is calibrated and optimised to give higher power output than the the original 0.7w.

Calibration is easy, follow the instructions to optimise the rx and tx.

If you have the Qrp Labs GPS unit, make a 4 way lead to connect the GPS to the QRX PCB. This is not clear in the instructions.

The GPS is powered from the 4 way connector on the QCX pcb – no external power needed for the GPS – make sure your pin to pin connections are correct by referring to the manuals and schematics for both units.

By selecting the correct menu function, the GPS will set the frequency offsets etc in less than 30 seconds and you are ready for the tx optimisation.

PCB in the custom case

Hans produced a comprehensive video showing the procedure for optimising the BPF and how to increase the TX power.

Video here

Following the guidance on the video, 2 turns were taken off the torroid and the others either pinched or expanded as described. Power output increased from 0.7w to 3.8w at 12v.

At 13v the power was just over 5w.

Text book tuning!

The last thing on the list is to source a 5.5mm/2.1mm power connector to marry up with the Bamotech supplied power socket – frustrating that they dont supply the power plug with the case kit.

RS components in the UK have the plugs, but with £4.95 postage on an 88p plug, it is a bit steep.

3.5w at 12v

Very happy with this radio, a lot of thought has gone into the design and the user manuals, and using a home built radio is very satisfying.



QRP Labs QCX 30m kit

Whist the current lack of travel is frustrating, and the enforced “house arrest” isn’t helping much, it has given the opportunity to make progress on some of those projects that have been gathering dust for a while.

Some time ago a QCX 30m kit arrived in the post from Hans Summers of QRP labs. The kit is well packaged and contains everything you need to get on the air. I must congratulate Hans on the quality of the build notes, all 150 pages of them. This is not as daunting as it sounds, as experienced builders can skip a lot of the information, and new builders can take in the many tips and step by step instructions.

The radio is a single band 5w QRP CW only radio that has a whole host of features built in including CW keyer, CW decoder, test equipment, LCD display and ability to link to a GPS time source for WSPR transmissions and frequency calibration.

It took me a couple of nights to build, and the excellent instructions saved any problems when winding the torroids.

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QCX PCB Completed

Once built, and checked for short circuits, power was applied, so far so good, no smoke! The next job is to set up the LCD, turning the brightness pot up a little illuminated the display with a prompt asking the builder to choose the band – in my case 30m (Band choice is chosen by the BPF that you build and fit to the PCB). The next step is to set up the receiver, again step by step using the built in test equipment and covered in great detail in the build notes.

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At last it was time to test the TX, with a watt meter and dummy load attached, the transmitter can be tested by pressing the in built microswitch (that also acts as a straight key) the power meter kicked over to 0.8w output, not bad for a first transmission, at least there was no smoke. Using the inbuilt “key” for a quick CQ G4YTD instantly decoded on the screen. This feature can be turned off, but is a good aid for new CW operators.

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First TX

Frequency offset against display was a little off when measured on a frequency counter. Hans has this covered by use of a GPS driven signal source. The QCX can take data from several GPS units, but QRP labs also offer a low cost kit to build one. I purchased one with the QCX, the build took around 1 hour to complete. At the time of writing I am waiting for a 4 way molex connector to arrive in the mail, and will then use the GPS to calibrate the QCX further.

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QRP abs GPS card

The satisfaction of listening to 30m on a home built radio took me back to when I was first licensed in 1984 using a home brew HF rig, who needs the latest gazillion £ Yaewoodcom radio to have fun?

Next steps on this project are to tweak the torroids to up the power a bit closer to 5w, and finish calibrating before boxing up in the Bamotech enclosure and giving it an airing.




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