Posts Tagged ‘SMD’

630m Transverter Project

I've ordered parts from Digikey for the summer workbench project, a 630m transverter. With the nice 630m WSPR signals received here from Roger (VK4YB) this spring, I think it might be possible for us to work each other using JT9, if the path continues to improve over the next few seasons. On more than one night, Roger's signal was at JT9 QSO levels and had we been on a schedule, a QSO may have happened. Roger's signal was peaking late in his evening, which for me will require making schedules in the wee hours of the morning.

I've been wanting to build another SMD project for some time since making a little SMK-1 40m transceiver several years ago. This was a very inexpensive kit put out by the NorCal QRP Club as a way of introducing SMD construction techniques to beginners. I found working with the 1206 sized parts (basically the largest ones commonly available) to be fairly laborious and would only solder a few parts at a time before setting it aside for the next day. I think my frustration had a lot to do with my positioning and soldering methods and I'm anxious to try doing it with a more refined technique. As I recall, there were 72 SMD components on the board and it took me a couple of weeks to finish it all.

My SMK-1 40m SMD transceiver
Although I was dreading the initial smoke-test, since troubleshooting would likely be a challenge, the transceiver fired-up with no problems and I made dozens and dozens of contacts with it. My QRP logbook indicates 27 states were worked with the little 350mw transceiver. It looks like this kit may still be available from Pacific Antenna but I have not confirmed if that's the case.

The parts I have ordered are also 1206 sized but the older I get, the smaller these things seem to look. The transverter will be based partially on the popular G3XBM circuit but will eliminate the PA. Instead, I'll just use a few volts of the transverted squarewave signal and a doubler, so that I can feed the signal directly into my present homebrew amplifier which uses two switching FET modules into a power combiner. Hopefully this system will let me run several of the non-linear digital modes such as WSPR, JT9, JT65 etc.

My 630m PA

As a way of getting back into the SMD-soldering groove, I have ordered and now received, an "SMD Practice Kit" from E-Bay ... a real bargain at $1.78!

courtesy: Tradeworld2105

Although there are many similar practice kits being offered on E-Bay, this was the only one I found that had two IC's to practice with ... all of the others had just one. Since the transverter's doubler circuit has an IC chip, a couple of practice opportunities will be helpful. My only hope is that I don't run out of SMD steam with the practice board before getting down to the actual transverter board.

As soon as the parts arrive from Digikey, I'll start designing the transverter's PCB ... but with all of the usual distractions of summer, as well as trying to maintain vigilance on the magic band once again, my summer project may not progress as quickly as I hope.

All of this assumes that my old eyeballs hold out as well.

SMD Kits

I've been intrigued for some months now by the proliferation of SMD parts kits widely available from Asian manufacturers being sold on E-Bay. Resistor, capacitor and inductor kits, containing significant numbers of standard-value parts and in various sizes are being offered at attractive prices. With many sellers throwing in free-shipping, I find myself being tempted more and more to press the "Buy Now" key and fear that I will not be able to hold out much longer.

I have had limited experience with SMD parts, when building a small 40m QRP transceiver several years ago called the SMK-1. As I recall, it had 72 SMD parts....the bigger ones, 1206 size. I recall finding the assembly and soldering of these SMD parts to be somewhat tedious and less than enjoyable. I usually only soldered a half dozen parts at one sitting. After a few weeks of periodic assembly, I was delighted to see the circuit come to life once power was applied as I was definitely not looking forward to trouble shooting the board! Perhaps my technique of fluxing and the method of holding the component in place with a homebrew 'third-hand' device was not ideal or maybe my soldering iron was not properly sized for the job but I do have a desire to try it again.

A 630m transverter, now planned out, would really lend itself nicely to SMD construction but realistically, the only size I would consider is 1206 at the smallest.


 Why I am really contemplating the purchase of more SMD parts is somewhat vexing to me....perhaps it is simply my 'concrete-sequential' thinking style making me lust after all of these tiny parts, with all of them so neatly organized in their holders, begging to be brought to life by my own hands. Or maybe I just want to prove that my 66-year-old eyes and hands are still capable of working with these things.

Someone talk me out of this before it's too late.

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