Balun practical comparisation

  Palstar AT1KM 1:4 ruthroff balun compared with homemade 1:1 current baluns outside the tuner. The goal is a practical comparisation between these baluns. I made two 1:1 current baluns specified to the instructions from G3TXQ, A useful article can be read here:

https://gm3sek.files.wordpress.com/2019/01/G3TXQ-RC.pdf

A tuner balun is made with bifilair windings since it doesn't need to have a 50 Ohm impedance and unwanted impedances can be tuned out besides that it can withstand higher differential-mode voltages.

 I took the design for the low bands and higher bands. 17 windings on two FT240-43 ferrite rings for the low bands and 9 windings on three FT240-52 for higher bands. To keep the rings together I wind ptfe tape on it first. I decided to wind the ptfe wires in ptfe tape as well to keep them as close together as possible.

Balun under test

The FT240 ferrite rings were bought from fellow blogger PA3HHO who has a lot of info about antennas and HF transformators/chokes on his blog.

  The baluns are doing a excellent job balancing. Though, is it really better as the internal 1:4 balun inside the AT1KM?

My RF current indication meters are having a scale from 0-100% and a little more. Good enough to compare. A test was made with 50W FM input.

Band	%Left	1:4	%Right		%Left	1:1 LB	%Right	%Left	1:1 HB	%Right
80	60		60		60		55	60		60
60	20		70		35		25	30		30
40	110		110		110		110	110		110
30	105		110		110		110	110		110
20	80		68		70		70	70		68
17	110		110		110		105	110		110
15	70		80		70		70	70		68

I didn't test the 160/12/10m. The 2x20m inverted-V isn't really efficient for those bands and so it isn't really interesting. 

  For me most interesting is my favourite 60m band. It is clearly not in balance with the internal 1:4 balun. But is with the 1:1 baluns. However I expected higher currents, not only on 60m but on the other bands as well. Interesting to see that balance on other bands is almost equal.  Overall you don't see much difference at all. The internal 1:4 balun gives some more current on 20m and 15m. Actually I didn't expect this outcome of this comparisation, The Palstar AT1KM performs much better as expected, even with the 1:4 ruthroff balun inside.

On the right you see the baluns. The boxed one is made for the higher HF bands and designed to fit below my multiband vertical between the CG3000 autotuner and the antenna. It doesn't feature any PL connector, only terminals.

I really do not expect any change in signal strength with all baluns. I also monitored noise on receive. It is all the same as soon as I tuned to a 1:1 SWR. Theoretically common mode surpression and balance would be a lot better with the 1:1 baluns and many articles describe much more current output. However in the "real" world I don't see much difference. 

I have to write though that I don't have that good measuring equipment of course. Others will read this and tell me I should use certified and calibrated equipment. I don't have the money for such gear and I like to build these things myself. I don't know how much the outcome would differ except for some real current numbers in ampere instead a 0-100% scale. Besides that I measured it on my inverted-V which can differ from other antennas and environments. There are so many variables that can have a influence that I can't write if I'm right with this practical balun test.