DB6NT 1.3GHz Transverter MKU 13G2B kit (/cont.)
The MKU13G2B Kit:
This is not my first Kuhne Electronics kit. I have previously built transverters for 13cm and 9cm, so I was looking forward to working on the 23cm kit. Kuhne make the manuals for their kits freely available for download so I had already read through it before the kit arrived. I knew what to expect. Typical of German efficiency, the components are all pre-packed in two 'hobby boxes', for want of a better description. The semiconductors, connectors and larger items like helical filters etc are supplied in the larger of the two with all the smd Rs and small Cs in the smaller one. My wife likes the latter for keeping her ear-rings in!
As it says in the manual, this is not a kit for beginners. For one thing, the tin-plate box first needs to be soldered together. This is best done after the PCB is 'trimmed' (small fillets need to be filed so as to accommodate the overlaps where the case sides join). I also like to mark and drill all the necessary holes prior to soldering the case together . . . this is just my preference though. Also, like all DB6NT transverters, this kit relies heavily on surface mounted components which require a steady hand and some degree of 'special' tools. A 'pencil tip' soldering iron is a must, as is super-fine solder (SWG34) . . . which brings me to a 'thorny' subject . . . 'the curse of RoHS'. I haven't previously mentioned it but the PCB is gold-plated. And you could be forgiven for thinking that this is to ensure low resistance tracks and that the board does not deteriorate over time, both of which are valid. However, it is more than likely that this is actually one of the good things to come out of RoHS, since a board 'tinned' with lead-free solder would look terrible. I don't even know if you can plate a board with that hideous stuff! If you want a board full of dry joints, then use lead-free
I actually used two different soldering irons since I find that the pencil tip bit doesn't quite heat up the 'lands' that are through-plated to the ground-plane and are in close proximity to the side-walls. For these problematic 'lands' (or pads), I use a 'standard' bit.
There is an assembly order suggested in the manual . . . and quite right too. This involves first fitting those top-side components that require soldering to the ground-plane . . . the helical filters. I believe these are Toko units. If you look at the numbers on the filters and compare them to the numbers on the box, you will see that they don't match. I know for a fact that several years ago Toko changed their filter numbering scheme and I think that Kuhne haven't got round to changing the annotation on the boxes yet.
solder! If you want the figures, lead-free solder is 99.8% Tin, 0.2% Copper. Tin is actually more dangerous than lead, since a simple cut from a piece of sharp tin can lead to blood poisoning. Lead, on the other hand needs to be ingested to cause you lasting harm. However EU rules demand that marketable products be lead-free . . . and rules are to be obeyed. I used good old fashioned SWG34 60/40.
Gold-plated precision-etched PCB