[TowerTalk] Balun for G5RV

[jimlux]

On 2/1/11 1:19 PM, Rick Karlquist wrote:
>   On 2/1/2011 10:36 AM, Rick Karlquist wrote:
>> Alternately, you can make these out of "monster" speaker cable
>> or 12 gauge low voltage sprinkler zip cord
>
> I meant to say "low voltage lighting" zip cord.  It has very
> thick insulation.  Although meant to operate at 12V, it should
> be good for many 100's of volts.

100s of volts I'll go for (probably 300V for the UL listing)..

However, that stuff has a low melting point AND having that much 
insulation on it means that it has a hard time dissipating the heat. 
I'd rather go with something thin.  Almost ANY insulation more than a 
couple mils thick would have sufficient breakdown voltage (heck, people 
use enamel-ish magnet/motor winding wire: it's not enamel anymore, but 
polyethylene or polypropylene or some plastic, in any case)


getting the heat out of a choke is the challenge and, I think, the 
dominant power limiting factor.  (those bead baluns in a piece of PVC 
pipe filled with spray foam spring to mind as a not particularly 
wonderful thermal design)

5 Amps DC in 10 ft of AWG 16 wire dissipates 25*.001*10*4 = 1 Watt...

At RF, where the skin effect raises the AC resistance (a factor of 15 at 
10 MHz in an AWG 16 wire, roughly).. you're looking at dissipating a 
watt or so per foot of wire, not even counting the dissipation in the 
magnetic cores.
>
> HD sells a generic version of the famous name speaker cable at reasonable
> prices, at least in terms of copper at an all time high of $4.50 a pound.
>