http://elecraft.85.s1.nabble.com/Re-NOT-the-feedline-was-KPA-1500-faulting-on-6m-SWR-issues-tp7661502p7661545.html
ARRL Asst. Director, NW Division, Technical Resources
> 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
>
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