'KB',
For an RF ground length makes a difference because if raises the resistance going to ground. A ground ought to be the absolute lowest resistance if can be, otherwise that RF will go where it 'sees' the least resistance. If the resistance going to somewhere else is lower than that going to ground, it just ain't gonna go to ground. Since RF is an alternating current, and since 'resistance' in AC circuits is actually impedance, then that ground connection ought to be the lowest impedance you can make it. Since impedance is determined by the frequency of a signal and since lengths close to 1/4 wave lengths have lower impedances than lengths closer to 1/2 wave lengths (when 'end fed'!), then the length of a ground cable should be close to a 1/4 wave length. For 11 meters that 1/4 wave length is around 102 inches (8.5 feet). So an RF ground for 11 meters should be very close to 8.5 feet, either longer or shorter (shorter is better, if possible). Or another way of saying it is use odd multiples of 8.5 feet, not even multiples. And, since resistance still plays a part in all this, that odd multiple length of 8.5 feet ought to be as large as practical to reduce the resistance. What's best? A huge wire about 3 feet long, or shorter. Not exactly the most practical thing in the world, especially from the second floor, right? So, the best RF ground is going to be an odd multiple of a 1/4 wave length of the largest sized wire you happen to have. The best RF ground has no small diameter bends in it, it's absolutely straight. 'Nuther one of those "not too practical" thingys, so make it as straight as possible with big bends in it, not small ones. Compromising isn't always bad if you do it right. So, do it right.
And as an alternative, you can use a counter poise as an RF ground. A counter poise has the same characteristics as a 'dirt' ground. Low resistance, low impedances, as short as possible. So a piece of wire 1/4 wave length long, but laid on the floor will work too without even touching 'dirt' (I'm not counting a little dust as 'dirt'). There is a 'catch' though. Changing frequencies also changes the length of that 'ground' so sometimes it isn't the best in the world. The second part of that 'catch' is that all that RF going to ground is composed of electrons, a lot of electrons composes an electrical charge, and electrical charges can bite the @#$$ out of you! Insulate that counterpoise, especially the end of it, very well! It not only 'bites', it can start a fire or melt stuff too. That's sort of at the extreme end of things but still possible. That counterpoise also acts like an antenna, so count on lots of RF floating around in the house.
All of that above is about RF grounds, not about 'safety grounds' or lightning grounds. A counterpoise is NOT a safety ground. Neither is the 'RF going to dirt' type of ground, unless the conductor used is very large. It still won't be the best safety ground cuz it's probably longer than it could be because of the RF thingy. ... Ready to take up knitting yet?
And lastly, braid makes lousy grounding conductors if those conductors are very long. There's more resistance in a 1/2" braid than there is in a 1/2" wide strip of solid copper, or aluminum for that matter. Braid makes for good ground straps where they have to wiggle a lot and are short. Not for longer, stable runs. Unless it's 'tinned' it also deteriorates fairly quickly in weather. Ain't all this @#$ fun?
- 'Doc
PS - I just happen to have these knitting needles for sale....
