IMHO - W2FMI's book on baluns (& ununs) offers much insight on the subject
of power ratings associated with different Balun construction - highly
recommended reading. One may also find some good info on W8JI's web site as
well.
Depending on application, it is apparent that a well-designed balun need not
necessarily to be physically large. From my limited recollection, for a
well-designed balun, power is generally limited by the dielectric strength
of the insulation and the ohmic heating of the conductors. If the core is
getting hot - then something is probably wrong with the design. For some
low impedance high power balun applications, the challenge of close-spaced
windings becomes one of dielectric strength. Baluns wound with home-made
low impedance coax cable apparently offer some opportunity for advantage
here. For high impedance high power applications, the challenge of
controlling the stray capacitance associated with the wide spacing may lead
one to consider achieving the transformation in multiple stages using two of
more baluns connected in series.
Hope this helps answer at least part of your question. Perhaps someone will
chime in with more info on choke baluns.
Matt
KM5VI
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim
Lux
Sent: Monday, April 28, 2014 7:40 AM
To: towertalk
Subject: [TowerTalk] Balun/Choke power ratings
A recent post mentions various models of Balun or Choke with power ratings
of, variously 3kW or 5kW.
How are those ratings derived?
Is it "run X power into a matched dummy load" and the thing doesn't overheat
(by some TBD measure)?
Is it by computation from the breakdown voltage or current carrying capacity
of the wires (probably without allowing for the thermal design of the
package)?
Is it "I ran a Henry 5k through it at max power into my antenna and it
seemed ok"?
And then
what would be a "real" objective power rating method? Seems that one of
the key factors is the dissipation of whatever you're choking, although
if the Z is high enough, maybe that's insignificant.
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|