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It started out as a thought during the 2005 June VHF/UHF contest -- I need some equipment for 222MHz. This project, as featured in the January 2003 QST, has been in my mind for a while. I have an under-utilized Yaesu FT-817, and this would be a perfect companion. So, I built two of them. Why two? Well, most of the parts are SMD from Digi-Key; their minimum quantity is 10 for most items, and I needed one or two of most parts. Other items, such as the RF amplifier -- if you bought over $100 from RF parts, you got free shipping and a free hat. (hey, who can pas up a free hat?) Well, that's like two modules and one adapter. So, I built two of these units. One is mine, the other I sold on ebay. After recouping costs, I probably made about $1/hour. It was an enjoyable project, so I try not to think of that. The following picture is of the internals of the first unit I built. Total construction time wasn't too long -- Maybe about two weeks, working a couple hours, maybe 2 or 3 nights per week.
The underneath side of the unit -- all the parts are 0805 surface mount. I don't need a magnifier for construction, but I do use a 30x microscope for inspection after-the-fact.
My soldering station of choice is a Metcal with one of the smaller STTC tips. That thing is awesome. You can do fine surface-mount work with it, switch the tip and solder a penny to a sheet of copper. Tip to hand distance is only about an inch -- that gives you tremendous control. Total heatup time is about 6 seconds and you're ready to solder. The Metcal makes a new Weller look and feel like junk. That's the first unit. The second unit went together even more quickly. I replaced the front-end RF amplifier MMIC A6 (originally a MAR-3) with an ERA-3 (along with the bias resistor) that I had on hand. The specs show a very slightly better noise figure, slightly more gain and a higher IP3 figure. I think my second unit is just a bit more sensitive than the first. That could be all in my head, but that's fine. I think the second unit is just a bit neater, too -- by this time I think I had perfected my SMD technique, and all of the parts went on much more quickly and square on the board.
I built a 6-element yagi for the 2006 222 sprint. Made one contact with the unit. The one station I did hear was strong. Where was everyone else? Oh well. I'm awaiting the June contest to try next. I still haven't ruled out selling the second unit and building the DEMI 222 transverter; a bit more expensive but has 25 watts out.
Sun Nov 19 21:13:29 CST 2006 Update: Tested the unit out with a ham about 50 miles north of me. Works just fine, the unit isn't deaf -- I just wasn't lucky during the contest. I'm thinking that I'll build an external 25 watt amplifier for this unit - that should get me cooking with gas. This page last modified Sun Nov 19 21:16:39 CST 2006 by timc! |
