Topband: alternative to vacuum variables

[Tom W8JI]

> One of the reasons I have mot gone to high power on 160 is the cost of 
> capacitors for my omega match - at least $300.  Anyone know of any 
> workable alternative?  I remember someone writing about using coiled-up 
> RG-8, RG-213 or maybe Teflon coax.  Where can I find more information?

Coax isn't the best for two reasons:

1.) Transmission line effects increase voltage at the open end. This 
aggravates arcing issues
2.) They are lossy

Here's something to think about, Pete. The voltage across a capacitor is I^2 
* Xc

So if you have a shunt feed and use a long, thin, wire....you not only 
decrease bandwidth and efficiency, you also increase the voltage. A thin 
shunt feed wire requires higher Xc (lower capacitance), and that makes 
voltage increase and BW narrow.

Use a wire cage and tap the shunt wire down at a 50 ohm point, and voltage 
goes way down. Do it the lazy way and use an omega match, and you give up 
bandwidth and need higher voltage parts.

73 Tom