[TowerTalk] Ladderline - what are the facts??/

[Kevin Normoyle]

On the comments about balun heating/QRO, even for guanella current baluns with lower loss cores like Type 61 or 43:

I like this topic, because I've been wrestling with that issue for a 6:1 or 9:1 impedance match for a N6LF antenna. 
Feedline is ladderline. I actually wound three bifilar 6" diameter air core coils I was going to use to make a huge 9:1 
guanella balun, because of this loss issue, but decided that a commercial model based on cores (from DX Engineering)
looked like it would work well.  (heck, I started wondering about the loss I was going to get because of the length of 
the wires in my 6" coils too)

Sure there's some loss transmitting with the ferrite cores in a current balun. The thing is we should just count the dB, 
right? Especially if just being used on a single band. Why stress about higher frequency behavior if not being used 
there?...(I'm targeting 80M)

We have heat loss everywhere, at some scale. Why are we stressed about the balun? Mostly because of bad history in balun 
design, right? And the use of baluns in situations far from their target impedance. Or with not enough choking impedance 
at the target frequency. Or antennas more unbalanced then we thought.

But let's look at what's fundamental solvable vs unsolvable.

We accept some dB loss if we have a long coax...it's just that the heat loss there is distributed, so we don't worry 
about it.

This particular heat loss is concentrated in the balun, and there's a history of poor thermal construction for baluns. 
Not enough core material. Plastic closed containers. Etc.

What's wrong with losing 35 watts at a balun, (.1dB out of 1500W say) as long as there's enough ferrite material so the 
cores don't see a heat rise that changes the core behaviors, or melts insulation, (note that all the good baluns are 
moving to teflon insulation) and there's enough air flow or other thermal transfer? Heat is not necessarily the problem. 
Heat dissipation can be.

If the Balun is up in the air and in the direct sun, there are issues about raised temperatures due to that also. But 
with ladderline, the balun isn't usually at the antenna?

Maybe the real problem here is the inability to measure things well. i.e. we don't have techniques to tell us when the 
end result is operating in a situation a lot different than we expected.

Wouldn't it be cool to put temperature sensors on a core in a balun, and get remote temp sensing at all times? Then we'd 
have a lot more real-world information about this core heating issue, rather than lab data.

-kevin
ke6rad