Topband: alternative to vacuum variables

[Joe Subich, W4TV]

 > Making capacitors out of coax seems like an easy solution, however
 > they end up being fairly lossy due to copper loss.  Think about
 > it:  you would not deliberately make a capacitor long and skinny.

One way around this is to use multiple shorter sections in parallel.

One can also use series/parallel arrangements of fixed "doorknob"
capacitors to obtain the necessary voltage/current rating to pad a
lower capacity/wider spaced "breadslicer".

73,

    ... Joe, W4TV


On 1/24/2013 8:39 PM, Rick Karlquist wrote:
> Pete Smith N4ZR wrote:
>> 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?
>
> Making capacitors out of coax seems like an easy solution, however
> they end up being fairly lossy due to copper loss.  Think about
> it:  you would not deliberately make a capacitor long and skinny.
> The only thing that makes them workable at all is that the heat
> generated is spread out over a large area.  You would have to
> carefully evaluate your proposed design to see if it were feasible.
>
> Rick N6RK
>
> _________________
> Topband Reflector
>