Thursday, November 29, 2012

New dummy load and the BNC problem

While making a small impedance bridge I came across a small issue in one of the female BNC plugs, the central pin would turn/rotate while being attached by a male plug, I sorted the issue soldering a strong wire from the center pin to another plug since that was according to schematic, a pcb island preventing rotation and anchored would be another solution.

Now reworking my UHF capable dummy load ("Cogent" mints box) to a new shape  (top one on the picture)....

...the same issue arrived making me break one of the eight 100 Ohm SMD resistors (4 || 200 series), in the end I reworked all the load, because I was out of 100 Ohm SMD, to tree parallel 150 Ohm 1/4W carbon resistors. Probably will not go to UHF but goes nice to high VHF.

In the end this was the result:

Not pretty, but for now it works...

Another issue I got due to the poor manufacturing tolerance and construction on BNC plugs/adapters is this:

 The middle pin is just press fit on the stripe line between the two female plugs of the T adapter.
It failed probably after the second insert in the dummy load, one advantage of this happening is that if you made a small coupler link you can make a bird style plug...

...always optimistic but next time will have to get a better brand of BNC's.

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