neděle 2. února 2014

Remote symmetric matchbox - part 2

I finally got to soldering the PCBs for my tuner. Here is the picture of the result hooked up to my Bus Pirate for testing:

Bus Pirate hooked up to control boards and capacitor bank board.
From the left side: Bus Pirate; SPI to UTP convertor; Capacitor board; UTP decoder and 3x8 relay driver board
The capacitor board can switch in capacitances between (design values) 3.7pF and 947pF.

It consists of 8 binary switched banks where each bank has three sections in series (to increase breakdown voltage) with two caps in parallel in each (to improve current carrying capability). All capacitors are zero temperature coefficient (NP0) ceramics rated for 500V.

banktotalsection 1section 2section 3
1.3.7pF2x 5.6pF2x 5.6pF2x 5.6pF
2.7.5pF2x 10pF2x 12pF2x 12pF
3.14.7pF2x 22pF2x 22pF2x 22pF
4.30.3pF2x 39pF2x 39pF2x 68pF
5.57.6pF2x 68pF2x 100pF2x 100pF
6.120pF2x 180pF2x 180pF2x 180pF
7.231.9pF2x 330pF2x 330pF2x 390pF
8.480.7pF2x 680pF2x 680pF2x 820pF

Once I (create and) connect the toroid board and input balun, the tuner will be ready for field testing.

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