Tuesday 2 September 2014

Steve Weber KD1JV's MTR three-band QRP radio

I finally finished my new HF QRP toy and it works a treat. I put my name down for the latest Mountain Topper Radio (MTR) design from Steve Weber KD1JV a few months back. Steve only releases a limited number of his designs each time and I was lucky enough to get one.

The finished three-bad MTR QRP rig.
Steve's radios are legendary and include the ATS-3/ATS-4 and derivatives.

The latest MTR is a three-band 2.5-3W QRP transceiver that can be built for 40m, 30m and 20/17m. It can even be persuaded to go onto 80m apparently. It is very advanced with a built-in keyer, memory, attenuator, single character digital readout, Morse annunciation and much more.

The best thing is it is tiny – about the size of a pack of playing cards.

I attended the G-QRPconvention last October and was inspired by some of the tiny QRP radios people had there, especially Colin M1BUU who had some rigs that were real works of art.

I held fire on building it for a couple of months to see if there were any changes to the instructions. As it was, Steve had to send out another chip as the original keying algorithm wasn't quite right.

So, with new chip in one hand and a very fine-tipped temperature-controlled soldering iron in the other I tentatively set about the build.

First off, this isn't one for beginners. It is about 90% SMD and the parts are tiny. Having learned my lesson the hard way I used a large baking tray to work on in an effort to stop parts flying off, never to be seen again. As it was I did loose one part for a few hours but eventually found it in the carpet. With components just 1-2mm in length this kit is not to be sneezed at – or over!

I took my time, spreading the build over five three-hour sessions. Apart from putting three capacitors in the wrong place (which I was able to retrieve) it went together quite well. On power up it received first time and I was able to go through the set-up routines with no bother, using a PC with PSK31 software to set up the oscillator on 10MHz as instructed.

But then it wouldn't transmit any RF. I eventually tracked it down to a poor joint on the L18 output toroid – I hadn't got all the enamel off one of the leads.

Bear in mind that this board is only 8.5cm wide.
I managed to get 3.5W out on 40m and 4W on 30m with a 10.1V pack of eight Ni-Mh batteries. On 20m I got about 3W. After glueing the cores to the board to make the whole structure more rigid I found that other people have said you can probably get another Watt out on 20m by removing a turn from the two 20m toroids.

Adopting the “if it ain't broke don't fix it” methodology I'm happy with 3W!

Incidentally, when I took the photograph of the board I noticed that there was a stray filament of wire laying on a chip. This must have come from when I was doing the final wiring. I've now removed it, but it goes to show how a digital camera can be a Godsend with SMD construction.

So does it work? Oh yes!

My first outing on 40m at home brought back Gunner OZ6NF in Copenhagen who gave me a 559. Next up was Pascal F5UQE in Lille who gave me 589.

I think this is an excellent fun radio and ideal for backpacking – if only we had some mountains around. The nearest big hill is 150 miles away from here!

So how do you get your hands on a Steve Weber designed radio? First you have to join the “AT_Sprint” Yahoo Group. That's where Steve announces that he is going to make a quantity of kits. Secondly, when he announces that this is going to happen you send him an email. If you are then lucky you will be selected and have to pay via PayPal. Good luck – the interest level is very high.

Overall, it is a fantastic design and well worth making.

73 de Steve G0KYA

Update 3/9/14; Tried it out on 20m today and worked Switzerland, Spain and Belarus. Went back to 40m and worked Moscow. Sensitivity is pretty good - not quite an Icom 756 Pro3, but look how big it is! Lots of fun. 

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