Tuesday, September 22, 2009

N2PK VNA Reflection brdge

The reflection bridge was fairly easy to build. Most of the work was mechanical. The two male bulkhead BNC were very difficult thing to find. I could not find a local source so I had to buy them from Hong Kong (tnx eBay!) . All RF connectors are attached to the aluminum enclosure using stainless steel hardware.

Great deal of precision is needed when drilling the holes for the male bulkhead BNC connectors. There is not much mechanical "play" in these connectors and they need to match perfectly the female BNCs on the front panel of the VNA. Both connectors are exactly 2 inches apart. This picture also shows the two L-shape brackets connecting the bolts of the female BNC to the ground plane of the PCB. The brackets are soldered to the ground plane on both sides of the center pin of the female connector.

Same L-shaped brackets for the male BNCs. I had to remove some of the solder mask in order to make better electrical connection. Good ground connection is essential! The male BNCs have their own ground pins on the back side (a nice feature) - also soldered to the ground plane (visible at the very left and right of the board).

The finished reflection bridge. This side is "up" when the bridge is fitted onto the Detector 1 port - the normal position for the bridge during reflection measurements.

The reverse side of the bridge. This side is "up" when the bridge is fitted onto the Detector 2 port (optional).

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