I think I will try a roughly triangular loop for a start. It gives low visual impact, puts a lot of wire in the air, uses existing anchor points (trees), and brings the feedpoint and hardware back to the house window area. I have been given a late nineties ARRL handbook (great product, a real reference source...), and it mentions current baluns made from sliding a fixed number of ferrite rings over certain types of coax. What are the thoughts on building such a current balun for my purposes? As this is experimental it allows a balun to be quickly made that appears to need no enclosure, so if it doesn't work not much time or cost is wasted. Thanks for all the help!
A better type is a Current type BalUn. Probably a 1:1, but some people use a 4:1.
Tom W8JI has discussion about this on his site.
Here's one fed close to the ground with a 50 ohm feedpoint impedance.
Originally Posted by M6DFV
Most of your Q's have already been answered, but in the interest of redundancy:
Is a current balun something I could make, or is it best to buy one commercially?
Either. Not too dear to buy.
Has it to be tuned to the antenna wire lengths?
Does a multi band triangular loop depend on traps?
If a ladder feeder could be run from the apex of the "triangle of wire" by the porthole window, and in to my upstairs shack via that point, that would be fine, but how would I bring ladder feed through a wooden window from that has about a maximum of half an inch between brickwork and the glazing unit it supports?
The ideal would be feed-through insulators, as in this commercial product from MFJ: http://www.mfjenterprises.com/Produc...uctid=MFJ-4600
You could make up something like this with just feed-through insulators and close the window in it. Or replace a window pane with wood or plexiglass. Here's a nasty secret: I have at times just drilled two holes through the wood, plexiglass, or the sash and run wires through. Crummy design but it gets by for lower power, if no metal is within a few inches.
If none of these options please you, then use the coax-to-current-balun mounted outside. In all, this should take less work to do than to talk about!
I have no knowledge of ladder feeder, as in its physical size, or requirements when fed through things like window frames. Cheers.
Most of us use 450-ohm vinyl coated twin lead: two #16 or so conductors about 1.25 inches apart; or 300 ohm line, about a half inch wide. Makes no difference which you choose in your installation - 300 ohm TV twin lead would be OK.