QRP Labs QRSS/WSPR Kit (Part 1 – the Build)

I recently built and tested the QRP Labs “Ultimate3S” kit, and I wanted to share the experience, including an issue I had.

At $USD 135 the Deluxe 6-band U3S set looked like a fun if slightly challenging kit to build, and I’ve been wanting to get a WSPR transmitter on the air, because it’s a kick to see what sort of propagation you can get with very low power (less than a watt). The price includes the case, parts for 6 HF bands, and a GPS receiver, so it’s a lot for the buck.

There’s a lot of functionality packed into this unit, with support for many different modes. The packaging is innovative, with a stack of boards that assembles behind the LCD display which is fastened to the front panel of the case. The case looks very nice, and the whole assembly has a good fit and finish.

I built the kit as directed except for some minor differences noted below. This was sometimes a bit confusing because the construction documents for each board support various options. The documentation is good, but it takes a careful reading of the instructions to get them right. The only mistake I made and had to fix later was the jumper installation on the Base Board, which is different if you’re using the switched Low Pass Filter (LPF) board. I was disappointed that the schematics included in the documentation aren’t complete, and didn’t show the jumpers.

The kit uses all through-hole parts and required winding 18 toroidal inductors and one toroidal transformer. I know some people get anxious about winding toroids, but I didn’t have any problems with these. As I built each of the 6 LPF boards, I marked them by band with a marker, which helped later.  As I wound the inductors, I  checked the first few with an LC meter, and they were pretty close (within 20%). I didn’t adjust any of them based on the measurements, because I wanted to build the kit in the same way as someone who lacks test equipment. As I’ll get to later, I do recommend that you do some testing on the finished kit. For the Power Amplifier transformer, I used the “ten turn bifilar” option.

I deviated from the standard kit in two ways. The first is purely cosmetic. I replaced the supplied push buttons with some I had which have a much more ‘clicky’ tactile feel. The original switches worked fine, but I like the tactile feedback. The second is that I ended up not using the GPS board that came with the kit. I built that board and attempted ‘on the fly’ to add the components to make it work with an active GPS antenna I had on hand. That didn’t work. Rather than getting distracted by trying to make that work, I connected an Adafruit Ultimate GPS module that I had on hand. I’ve had great results with these in the past, and I knew that it worked with my active antenna, which was also from Adafruit. That worked fine, so I never went back and used the GPS board supplied with the QRP Labs kit. I did undo the modifications I made to that board and installed the supplied patch antenna, and the QRP Labs GPS board came right up and worked fine.

The kit design is very nice mechanically, and the boards stack nicely with standoffs. The case has enough room at add other modules like the GPS and the optional 5 Watt amplifier, and optional receiver board.

I scraped the paint off the inside of the panel around the power and antenna connectors for an improved ground, and added an SMA connector for my GPS antenna. It all came together well, and it’s a good looking unit.

The QRP Labs web site has a huge amount of information, and there’s an active community, with a dedicated discussion group. There are also a number of studies and investigations that have been done which contain some really valuable information.

In the next installment, a look at the user interface.


About Steve

I'm Steve Conklin, AI4QR I'm employed by Salesforce, on the SRE team for Heroku. Interests include Linux, open source software and hardware, electronics and music, and amateur radio.
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