[Elecraft] NOT the feedline

[Fred Jensen]

Nearly same experience Bob:  Sloping V, 135 ft legs, from top of 80 ft 
tower fed with homemade 600 ohm open wire using a DX Engineering 4:1 
"balun" [a strange, usually misunderstood piece of electronic apparatus 
often used for the wrong reasons] rated at 10 KW.  It warmed up 
noticeably at 1.2 KW RTTY use.  It helps to remember that one can 
saturate a ferrite core [especially when very hot] which creates a 
racket reminiscent of a non-synchronous spark gap TX.

73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 6/1/2020 1:48 PM, Bob McGraw K4TAX wrote:
> Based on my experience, balun power ratings are for MATCHED 
> conditions. It is rare that hams use a balun in a matched condition. 
>    Thus a 1:1 balun should see 50 ohms on the input and 50 ohms on the 
> output, while a 4:1 balun should see 200 ohms on the output and 50 
> ohms on the input.   In the case of a resonant folded dipole, a 4:1 
> balun is typically operating in a nearly matched condition. All others 
> combinations are unknown and random.
>
> I run about 500 watts on all bands.  My baluns are rated at 5KW! It 
> takes 3 or 4 big hunkin' pieces of ferrite to attain this power 
> level.   My 6 meter balun is a 1/2 wavelength electrically of RG-213.  
> No ferrite!
>
> Buy or build a balun of your choice.  Using an IR temperature gun, 
> measure the ambient temperature of the core.  Run about 1/2 rated 
> power carrier for 30 to 60 seconds.  Measure the temperature again.   
> If it is warm to hot, this is RF producing heat.   And likely 
> continuing will produce core failure.   This is not a good balun for 
> your application.
>
> One of my baluns work between the output of my KAT500 and the balanced 
> feed line connected to the center of a 256 ft wire.  That antenna 
> works 160M - 6M with zero issues.   Now, I do run a hybrid balun being 
> a 4:1 Guanella balun as a transformer, and it is fed with a 1:1 balun 
> for common mode rejection.
>
> Most single core, i.e. 2 or 3 cores stacked with 2 to 4 windings are 
> not at all a proper balun design   A Guanella balun will have 2 cores 
> with 2 windings and then another 2 separate cores with another 2 
> windings.  These are then wired to produce a 4:1 balun with good 
> common mode rejection.    Most "factory" 4:1 baluns are poorly 
> designed and built junk.
>
> See https://www.dj0ip.de/balun-stuff/ for further references.
>
> 73
>
> Bob, K4TAX