Talk:450 Ohm Ladder Line
calculate antenna size
When creating an HF antenna they say (they being experienced hams) that you should add about 2' extra to compensate for the inaccuracy of the magic number "468." According to the ARRL Antenna Book, the "end effect" due to the attachment of insulators at the ends of the antenna results in the approximately 5% reduction in length from the free-space 492/f to 468/f. The percentage varies slightly with different installation. Height of the antenna above the ground has a significant impact. Start with an estimated value based on a more realistic formula such as 490/f that results in a small amount of extra wire for attaching insulators. During tuning, twist the wire connections together or use clamps, then raise the antenna into position and measure. When it’s right, only then solder and weatherproof the connections.
