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Rigs for CW by Tony G8TDL

My personal favourite is the Elecraft KX-1 hand-sized QRP rig with the atu and paddle/keyer built in. It receives SSB and AM very well too and runs on a set of AA batteries for ages. All you need is a set of cheap earbuds and a bit of wire when you set off with it. I built mine in 2006 and I’ve taken it all over the place. I lent it to Chris G8AJM who sent me a pic of it on the the beach at Santa Monica. Chris also took it to New Zealand and was able to make contact with Brazil, France and some DXexpedition in Guinea amongst others. Proof if it was ever needed that the most important thing is a half decent aerial and a location where there is no noise! Some good pictures too of amateur radio in "middle earth!"

KX1 QRP CW rig on Napier Beach, north island NZ, a couple of weeks ago
 
KX1 QRP CW rig on Napier Beach, north island NZ, a couple of weeks ago

The KX1 is still available from Elecraft and it is a lot cheaper than the KX3 even with import duty and VAT. The K1, another QRP CW rig, is only a little bigger, so that’s also worth a thought.

At the other end of the scale, I’ve also built quite a few of the little Altoids tin things including some of those currently available on eBay. If you search for "Frog Sound QRP" there’s a little 40m rig which is very good.
 
Frog Sound QRP rig
 
The Frog Sound 40m QRP transceiver
 
In short:

- Works very well

- Receiver is as wide as a barn door. In a contest you’ll hear about 5 station all at once. you have to listen for the one that’s nearest your own sidetone to biologically filter it!

- Mine cost £7.94 including postage

- A couple of component values need to be changed. The original had 4 to 5 seconds delay switching from Tx to Rx, so I have no idea how anyone ever used that.

- Instructions are awful.

- Absolutely nowhere near the 3 to 4 watts claimed. 1 watt is no problem, and very useable, too.

- I monitored output for several hours into dummy load and it’s a very clean output signal. More than 44db down either side of quite a narrow band (I forget what I measured now).

- As well as the crystal oscillator there’s a crystal input filter. All the ebay ones are set at 7.023MHz, so I got a couple of 7.030 (where the QRP CW stuff is centred) crystals from the GQRP club for a few quid.

The Frog Sound TX spectrum
 
The Frog Sound rig TX spectrum

As a final note, I built one kit from ebay, loosely based on the "Pixie" which works, but it is a bit grim. This one cost £2.96 including postage. It would be fine to use as a QRSS beacon or suchlike, but to use it as a CW Tx/Rx you’d have to be a bit more committed than I’m prepared to be. The sidetone sounds like a goose f*rting in the fog, to quote Billy Connolly.

Oh and another final note…. If you want to build a keyer, so that you can type your CW through your computer or arrange a few buttons and a paddle, there are quite few free programs that run on an Arduino that do this. All you need is an optocoupler (Maplin £1.30) and a small Arduino - I use an Arduino Nano (about £8-00 on ebay).

73

Tony

G8TDL




Notes from editor:

Thanks to Tony for this article, which is adapted from an informative message he put out on the club email reflector.
 
Details on the Elecraft KX1 are here: http://www.elecraft.com/KX1/KX1.htm 
 

The single-crystal 7.023 MHz "Pixie" rigs can currently be found for as little as £2.28 on eBay, including postage from China. Only 28p more than the cost of a xtal should you want to retune it to 7.030 MHz!

Here is one example of an Arduino keyer: http://blog.radioartisan.com/arduino-cw-keyer/


 
 
 
 
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