Saturday, 25 August 2018

The QSX SDR HF from QRP Labs

QRP Labs started design and producing small QRSS/WSPR Beacon transmitters some years ago, along with a complete set of addons and other accessories that have evolved as the project progressed.  Last year, owner and designer of QRP Labs, Hans Summers, took his small company to a new success level with the launch of the QCX 5W Single Band CW/WSPR transceiver. Which has currently sold to date well over 5500 units, over various HF bands.  A fantastic project because it crammed so many full features into it's small pcb, including its inheritance from the WSPR Beacon, but with full frequency agility, CW decoder and included was a unique inbuilt test generator to aid alignment, never seen on such a low price product before.

The QCX has proved a QRP Labs British success story for such a niche product in it's own right.

Of course Hans (G0UPL) wasn't going to rest on his laurels and an SSB radio had been rumoured to be on the design board for quite sometime. Infact he had told me at the begining of this year, these projects takes a while before they hop off the design lab bench and reach fruition to complete into a working project.

So it wasn't no surprise that G0UPL has again used YOTA 2018 (Youngsters On The Air) hosted in South Africa this year, to pre launch the QSX a 10 Band HF SDR project. You could say that YOTA is used like a test bed to iron out any last minute technical and constructional difficulties, found, or encountered, before he begins to put the kit into full time mass production in a couple of months or so. Most of what the new SDR single/10 band rig will do and it's outlined specification, is set out on his website here: QRP LABS - QSX

 Photo G0UPL 

I was fortunate enough to have a short electronic messaging chit chat with Hans earlier this week, and he was able to put me well in the picture with one or two technical details about the project.

While emissions and spurs are all the talk of the town at the moment on another QRP project from another company not associated with QRP-Labs . The QSX will have "no" spuri issues!

Using 2 IRF510's in the QSX's linear HF PA, Hans reports the performance is excellent! The PA module being driven by two BS170's in Push Pull, giving an overall gain of around 26-28dB. This concludes in easily producing 10W across all HF bands using 12V.

Gain Flatness is better than 2dB across the spectrum between 2-30MHz. It is about 4dB down at 6m and 8dB down at 4m.Thus the same drive level that produces 10W across the HF bands gives a very useable 5W on the 6m band.

Hans also reports the linearity is excellent too!

Harmonics are low even before it even enters the LPF: 80m measurements 2nd harmonic is at -38dBc, 3rd -31dBc Making it very easy for the LPF to clean up what remains resulting in a very high performance radio.

All this is achieved using cheap Chinese IRF510's

Photo G0UPL

The heatsink is BIG!! Testing, it ran at 10W output for 1 hour continous 100% duty cycle, no forced air or cooling, the heatsink temperature was still reasonable about 40C over ambient.

Destruction tested at:

1) 20V supply.
2  25W output.
3) 15W 100% duty cycle for 15 mins.
4) Open load.
5) Short circuit.
6) Various mismatches.

All tests resulted in no failure.

Further reference watch the video AE4FH interviews Hans:

Friday, 10 August 2018

Forward thinking and food for thought.

Sorry there has been very little activity from me during the last few months, family stuff has taken up a lot of my spare time recently, and radio has been well off the menu. However I will try and get back into the Blog as our Summer comes to an end.

I was recently contacted by one of the Telford Hamfest organisers asking me to give a talk:

 We would like to invite you to give a "talk" at our "Telford Hamfest" QRP, orientated, would be great. The date for our Hamfest is Sunday September 2nd 2018. We expect to put on three "Talks". The "Talks" would last about 40(ish), minutes, with a Q&A after each, with a gap until the next talk. The timings are 11.30,12.30 and 13.30. I hope you are able to take us up on our offer Steve

The Telford Hamfest is a Radio rally which has been held around the Telford area for many years at various venues. But for a number of years has stabilised at being held at Coalbrookdale, Shropshire, and also now incorporates the G-QRP Convention as an added bonus.

Well Stephen had already decided he wasn't going to the Hamfest this year, so it all arrived too late! But it is with interesting thought what I would of talked about, and who actually put me up for this, I could name a few?

The last lecture I gave is when I ran a Packet radio BBS and node (GB7RUG) some 20 years ago. Talks don't just come together overnight, sorry I had no real time to prepare anyway. So Telford Radio club and G-QRP thanks for asking, I might do it next year if you give me enough time to think about it?

Actually by now I have mulled it over I have even thought in my dreams what I would of chatted about Hmmm! Humm!

See you all next year :-)