steveeh131047 wrote in news:46a67bfc-c375-4533-8df0-
:

On Oct 5, 2:10*am, Cecil Moore wrote:

Has there been any information published on loss and
transformation measurements for real world TLTs used
far outside of their design impedances?
--
73, Cecil, IEEE, OOTC, *http://www.w5dxp.com

Cecil,

Martin has some data under the heading "33ft Verticals and 4:1 Ununs "
he
http://g8jnj.webs.com/currentprojects.htm

Steve,

Here are the input impedance and VSWR(50),Loss graphs for my model of a
FT240 #61 with 12 bifilar turns with a 1000+j0 load.

http://www.vk1od.net/lost/Clip045.png

http://www.vk1od.net/lost/Clip046.png

Non-ideal transformation ratio is not a big issue for an unun used with
an ATU, voltage withstand and loss are higher priority.

The balun loss data in the article at http://vk1od.net/blog/?p=568 was
obtained by measuring the balun using a VNA, and creating a spreadsheet
that solved the balun + load network for an arbitrary load impedance. The
spreadsheet is revealing, as one can immediately see the broadband
peformance of the balun with extreme loads, R and X in arbitrary
combination.

What I do know is that it is superficial to describe a balun (or unun)
with just two metrics such as 5kW, VSWR1.5... but have a look at
commercial baluns, that is how they are often (mostly) sold. There is the
odd manufacturer that gives a loss and VSWR curve on a nominal load FWIW,
but I have not yet seen any manufacturer publish a set of S parameters
covering the operating range.

I am not naive about magnetics, they are challenging devices, but at
least in the ham radio market, it is more black magic than good sense.

BTW, if you look at the loss graph for this device with a 1000+j0 load,
and assume that it can safely dissipate perhaps 20W continuous, it is
capable of less than 1kW continuous at 30MHz, but some manufacturers
build such a transformer and rate them at 5kW or more. With a load
impedance of 4k+j0 (eg a full wave dipole), the loss is even worse, and
the continous power rating even lower.

Owen