[TowerTalk] 450 Ohm Window Line

[Jack Brindle]

The answer is that "it depends." If the metal is running parallel to the feed line, then there will be coupling and that distance is insufficient. If, however, the feed line just crosses the metal (preferably at right angle), then that should be just fine. This is another case of try it and see.

Apparently there are articles on the web pointing to a "magic length" for open-wire feed. The person who asked me about it had a run shorter than the number, and wondered what to do about it. Don't coil it!!! That would couple the feed line back into itself and destroy the balanced properties. The real answer is to use what you need to get to the antenna and handle things with the tuner. If you find a voltage node near the shack (and thus RFI), you can add feed line length out in the open to move the node. In the days of tank circuit tuners, we would just move the coil taps out to adjust the coupling.

Good luck! Open wire line is magical in itself.

Jack Brindle, W6FB

Sent from my iPad

On Jun 15, 2013, at 9:34 AM, Marshall Stewart <marsh at ka5m.net> wrote:

> What is the required spacing for window line from metal objects, like rain
> gutters? Best I can it is "several widths" of the window line. So if the
> window line is say 1-inch wide, would 3 - 4 inches be okay?
> 
> Marsh, KA5M 
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