Construction
The connector - N-type
N-type socket round "through bulkhead" came from R.S. number 112-0773. Packaging says Telegartner (Manufacturer presumably) Type N-Einbaubuchse J01021A1084 Tel +49 (0) 7157/125-0 Fax -120
The biquad ("bow-tie" bit)
The "bowtie" section was made from a length of copper at least 400 mm (0.4 metre) long. The wire came from standard twin-and-earth stiff household mains wiring. By holding either end of the wire with a pair of pliers and giving it a sharp tug the wire was straightened. Leaving about 20 mm before starting, the bowtie shape was folded into the wire using the pliers, with the side of each square being 32 mm. The edge of the pliers was useful to obtain right angles. Both ends of the wire end up in the same place once the "bowtie" is formed. These were soldered together and bent 90 degrees out of the plane of the bowtie, ready to be soldered to the casing of the N-type connector. The "bowtie" then had an extending piece of wire soldered to it at the point where there is a 90 degree bend joining the two squares together, ready to be soldered to the centre pin (solder bucket) of the N-type connector.
Soldering
We worked out where the rear disc (groundplane) would sit when the N-type connector was affixed to it, and then both extending wires we cut so as to stand the "bowtie" off the back plate by 18 mm. The centre pin was easy to solder because it has been tinned by the manufacturer. Soldering the other extending wire to the casing was not so easy. It required the surface roughing with sandpaper, and then tinning with a lot of heat until the solder flows. Once the casing and the end of the wire extension was tinned soldering was easy, while the connector body was still hot. At this point the dialectric (the white bit around the centre pin) started to go a bit soft. We were careful not to move the pin, and ensure it was straight before it cooled.
link for completer articel : http://flakey.info/antenna/biquad/
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