steveeh131047 wrote:
But one question would be how to build this ideal 1:9 transformer
which maintains its transformation ratio and exhibits zero loss across
the wide range of impedances and frequencies involved.

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

Owen,

If I've managed to read my lab notes correctly, these were the
differences in loss (ground+feedline+tuner) - with and without an
ideal 9:1 transformer at the feedpoint - for a 33ft vertical over
average ground fed with 50ft of RG213. I assumed ground losses of 20
ohms. Positive figures indicate that the losses were lower with the
transformer:

160m -1.6dB
80m +6.02dB
40m -2.3dB
30m +2.1dB
20m +4.4dB
17m +3.86dB
15m -0.55dB
12m +1.6dB
10m +2.9dB

Of course this data was for one specific scenario, but I guess you'd
look at it and say that for this case, on balance, the inclusion of
the transformer was of benefit. But now factor in some realistic
transformer losses and it might not look so clear cut.

73,
Steve G3TXQ

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

73,
Steve G3TXQ

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

On Oct 5, 10:14*am, Owen Duffy wrote:


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

Owen,

Agreed. But the "non-ideal transformation" will result in changed
feedline losses and tuner losses. May be better, may be worse

I enjoyed reading your balun loss article. "66% of the transmitter
power converted to heat inside the ATU" will be a surprise to many
folk. I can replicate almost the exact set-up you describe: G5RV
half-wave of ladderline4:1 voltage baluntuner; so If I can find
the time I'll try to measure the rate of temperature rise inside the
tuner case when it's handling 100W CW, and then stick a 60W light bulb
in the case and measure the rate of temperature rise again.

73,
Steve G3TXQ

Thanks for the numerous comments on the unun / balun, but I read nothing on the
possible convenience to use a 300 ohm flat ribbon in place of coaxial. No
interest for that issue?

73

Tony I0JX

On Mon, 5 Oct 2009 17:39:28 +0200, "Antonio Vernucci"
wrote:

but I read nothing on the
possible convenience to use a 300 ohm flat ribbon in place of coaxial.

On Sat, 03 Oct 2009 13:39:12 -0700, Richard Clark
wrote:

If your BalUn has already done the bigger job of turning a High Z to a
modest one, the common logic for the need for twin line has also been
diminished.

73's
Richard Clark, KB7QHC

If your BalUn has already done the bigger job of turning a High Z to a
modest one, the common logic for the need for twin line has also been
diminished.

Yes but my question regarded the advantage of twin-lead vs. coaxial in that
particular application where impedance is uncontrolled.

73

Tony I0JX

On Mon, 5 Oct 2009 21:17:26 +0200, "Antonio Vernucci"
wrote:

Yes but my question regarded the advantage of twin-lead vs. coaxial in that
particular application where impedance is uncontrolled.

http://www.vk1od.net/calc/tl/twllc.htm

73's
Richard Clark, KB7QHC

steveeh131047 wrote in
:

On Oct 5, 10:14*am, Owen Duffy wrote:


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

Owen,

Agreed. But the "non-ideal transformation" will result in changed
feedline losses and tuner losses. May be better, may be worse

Almost always, but probably more often for the better.

BTW, I gave a brief description of the FT240 #61 12t unun, but didn't
mention the winding details, they are 0.8mm wire spaced (centre to
centre) 3.2mm and permittivity 1.2 which describes a winding with 0.8mm
PTFE insulation for high voltage withstand, an 'ATU unun' in commercial
talk.


I enjoyed reading your balun loss article. "66% of the transmitter
power converted to heat inside the ATU" will be a surprise to many
folk. I can replicate almost the exact set-up you describe: G5RV
half-wave of ladderline4:1 voltage baluntuner; so If I can find
the time I'll try to measure the rate of temperature rise inside the
tuner case when it's handling 100W CW, and then stick a 60W light bulb
in the case and measure the rate of temperature rise again.

Keep in mind that ferrite cores heat (and cool) very slowly. One could
easily be fooled into thinking that there isn't much heat dissipated in
a short test, but after an hour of operation, the core is still heating
at a substantial rate. This is one of the things that saves the bacon of
manufacturers of 5kW and 10kW continuous rated baluns, they are not
usually called upon to operate at high duty cycle for long enough to
reach the Curie point.

Calorimetric measurments are problematic, they sound simple enough, but
latency my mean it takes hours to reach close to maximum operating
temperature.

The greater worry is that this manufacturer, and probably some others,
use thermoplastic insulation to support the coil, which could result in
damage if you operate the ATU long enough to reach operating
temperature. Do so entirely at your own risk.

At one time, I had two identical ATUs, and I attached one with a 600+j0
load to the tx on 1.8Mhz and adjusted for VSWR=1 on the input. I
replaced the load with another ATU backwards and with a 50+j0 load and
adjusted the second ATU for VSWR=1 on the input to the first ATU. I then
read the power into the 50 ohms load and out of the tx using a Bird 43
and calculated the loss. The loss in the first ATU under those
conditions can be approximated by allocating half the total loss. This
test indicated quite high loss, and the case was quite warm near the
balun after just minutes of testing. BTW, this was the same type of ATU
as in the article you mentioned earlier.

In the example article, about 26% of the tx power is radiated on 80m.
That sounds pretty awful, but it should be seen relative to say 80% as a
reasonable system efficiency for a multiband antenna.

Owen