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Mike, NI2S's Ham Blog

Page 13

 19-JAN-08: Automatic Antenna Tuner Build.  lC  Board Assembly

 So onward I construct the 2nd half of the Antenna tuner.  Overall, the compact antenna tuner assembly is a fun challenge to build.  Lots of parts to solder, and some parts - especially some of the capacitors bent at 45 and 90 degrees require patience and a bit of finesse.

I soldered all of the 5v relays, with no problem....the suggestion in the manual to solder two leads per relay, and then reheat them to make sure the relays are flat against the PCP worked fine and I had no trouble here.  In the final assembly there is ZERO clearance for these relays, so you better be sure they are as flat as flat can be on install.

Installing the capacitors was a bit tricky, since the bodies of the relays prevent you from soldering on the back of the PCB, but patience, a good solder iron, and an articulated magnifier is all that you need to do it right.  Here is a side-on shot of the tricky cap installation, in the same orientation as the manual illustration:

   Installing the toroids took time, but was not really a problem.  Soldering the wires in the pads was the most challenging part.  So far, I have really not found winding toroids all that terrible.  It is tedious, but it doesn't take long to 'lace' up a toroid.  And don't forget I count my windings four times, just to be absolutely sure they are correct.  Most of the time here was spent ever so carefully trimming back the leads so that the toroids fit just right on the PCB.  Six of the torroids on this board rest atop little rubber pads to prevent shorting.  So trimming the leads to account for the rubber pad, soldering the leads, then installing the pads took some time.  But like everything else in this kit, patience is all you need to get it right.  Here I experienced another goof.  While I was winding one of the torroids, it popped out of my hand and landed on the concrete floor, breaking in two.    There are no spare cores in the kit, so I must send to Elecraft for a replacement.  This of course will prevent me from completing the Auto Antenna Tuner assembly.  But I can continue with the main RF board assembly while I wait for the replacement core, so it will not stop me.  The enameled wire for these cores can be a bit on the slippery side, and I had a couple of these cores pop out of my hands as I wound them (only one broke) so if you are not working in a carpeted area, it's a good idea to put something soft down - a pad of some sort - and old thick bath towel - a carpet remnant - something soft.  Note I have 'medium' sized hands, so the problem here was not fat fingers, but slick slightly springy wire.

Anyway - here is the finished LC Board with the one torroid missing....

Next are the two wire harnesses and then sandwiching these two halves of the Antenna Tuner together....on the next installment of This Old Kit.....

19-JAN-08:  The Auto Antenna Tuner accessory kit is as complete as I can make it sans missing toroid.  I did not have much trouble with the wire harnesses except that when you strip short lengths of wire, the insulator tends to slide.  Crimping/soldering the individual pins for the connector was tedious small work.  Couldn't have done it very well without the 5x magnifier.  I have also started wearing non-prescription reading glasses for even more magnification for the tiny work.  Here are several pics of the ATU assembly.  In the far left pic below, take note of the clearance between the two BNC antenna connector bodies and the bank of 5v relays - there is none.  When Elecraft says a component must lay flat on the PCB, they mean it!


Now, on to finish the RF motherboard....