what balun to use

[p.larner]

my feeder is 450 ohm windowline,what sort of balun do i need to go to a 50 ohm atu input.9-1?.

[A.Z.]

1:1 those 450 Ohm are the CHARACTERISTIC impedance of the feeder, NOT the impedance seen at its end, and "50 Ohm ATU" is total nonsense, go on refusing to LEARN

[Andy Chee]

use a 1:1 balun

https://www.dj0ip.de/balun-stuff/tuner-baluns/

As commented above, do not confuse transmission line characteristic impedance with antenna impedance, they are two separate concepts.

[A.Z.]

https://en.m.wikipedia.org/wiki/Characteristic_impedance

you want THIS one

https://www.dj0ip.de/rf-cmc-chokes/different-kinds-of-chokes/d2-guanella-choke/

[A.Z.]

https://en.m.wikipedia.org/wiki/Characteristic_impedance

you want THIS one

https://www.dj0ip.de/rf-cmc-chokes/different-kinds-of-chokes/d2-guanella-choke/

and then, considering your limitations, you may also have a look here

https://owenduffy.net/transmissionline/stcm/index.htm

https://www.m0mcx.co.uk/how-to-use-dual-coax-feeders-as-ladder-line/

https://www.southslope.net/~kb0sk/antenna.html

https://archive.org/details/spencerpdf

but then, I suspect I wasted my time once more

[A.Z.]

the thing you MUST understand is HOW a BalUn (a current one, not a voltage one... we may fathom it later on) works, and WHAT and HOW/WHY it does it, let ASIDE impedance transformation, start FLAT, and if you'll get a grip on that IF you use your brain ...

[vk4ffab]

my feeder is 450 ohm windowline,what sort of balun do i need to go to a 50 ohm atu input.9-1?.

As per your other thread, you need a 1:1 at the dipole feed point and a 4:1 at the tuner. The 1:1 keeps the legs of the antenna balanced and isolates the window line, the 4:1 just changes the impedance extremes into something the atu-100 can handle and transforms the balanced line into an unbalanced tuner.

Antenna system wise, this is then no prune and the losses will be acceptable. You do not need to measure 50 ohms at the tuner, in such a situation.

[p.larner]

can i put an ugly choke/balun at the feedpoint then connect that to windowline,then a 4-1 balun at the tuner end then?,heres the polar plot of my antenna windowline connected to my vna,no balun or coke etc,i already have an ugly balun made from rg-213 on an 6 inch pipe with 20 turns on it,thats why i ask.

[p.larner]

i am told a 1-1 balun should be bifilliar but have found this,whats best 3 wire type or 2?,just seems confusing to me one lot of folks saying it needs to be 2 wire.

[Andy Chee]

I’m inclined to believe two wire. Can you post a link to the person saying three wire?

This balun is constructed with bifilar windings:

https://owenduffy.net/blog/?p=687

[p.larner]

was this in the pic,just not sure what number of turns on a ft-240 43 core to wind

[Andy Chee]

Ok, that three wire 1:1 balun in your image is a voltage balun, which is incorrect for your purpose.

For your purpose, you need a 1:1 current balun.

https://vk6ysf.com/balun_guanella_current_1-1.htm

For 80m, you will probably need about 16-17 turns, just fit as many as you can in one layer without overlapping layers.

[A.Z.]

Ok, that three wire 1:1 balun in your image is a voltage balun, which is incorrect for your purpose.

For your purpose, you need a 1:1 current balun.

https://vk6ysf.com/balun_guanella_current_1-1.htm

For 80m, you will probably need about 16-17 turns, just fit as many as you can in one layer without overlapping layers.

the guanella above isn't bad, but I'd rather suggest this one

https://www.dj0ip.de/rf-cmc-chokes/different-kinds-of-chokes/d2-guanella-choke/

and then, for the 4:1, I'd suggest this other one

https://www.m0pzt.com/blog/4to1-current-balun/

both are easy to wind/build and they can all use the same FT240-43 toroids, three of them will suffice for the task, then it remains to see if he really needs a 4:1, see, if the impedance goes too low, the ATU he's using won't be able to match it

[A.Z.]

can i put an ugly choke/balun at the feedpoint

A so called "ugly balun" will ONLY be effective on a limited frequency range, it may be ok for well balanced SINGLE BAND antennas, but if used on multiband antennas or unbalanced antennas, not only it will have little effect, but it may even make things WORSE !

[p.larner]

well ive made this(see pic),i am told i need 2 cores for the 4-1 transfo,guess i may as well try it,am i best fitting it at the rig side of the atu?

[A.Z.]

GFYBOH

[Andy Chee]

well ive made this(see pic),i am told i need 2 cores for the 4-1 transfo,guess i may as well try it,am i best fitting it at the rig side of the atu?

Connect your balun(s) between ATU and antenna feedline.  NOT rig side!

[p.larner]

Paul M3VUV
10:40pm   #364   
well i am trying this,firstly the windowline goes into the choke as in the first pic,then goes to a 4-1 balun made with 2x 240-43 torroids then to the tuning elements in the tuner,pic 2,should that be ok?,all 3 cores are 43 material.

[p.larner]

ive wound the ballun linked by andy chee,but used thin coax,is that ok,i think its rg-174.

[A.Z.]

ive wound the ballun linked by andy chee,but used thin coax,is that ok,i think its rg-174.

and, the question is ?

A suggestion, considered the sub-optimal setup of your "so-called" doublet antenna and the problems you keep facing, consider the idea of setting up a terminated antenna, like for example a T2FD or a terminated horizontal loop antenna, feeding it directly with coaxial cable through a 16:1 BalUn followed by a good Guanella choke, I know you'll keep ignoring the suggestion as you kept ignoring the requests to sweep your antenna using the VNA, but given that you're still wandering in the dark I thought it was the case to refrain the suggestion, and in case you don't understand what a terminated loop is, just start here http://hflink.com/antenna/#BBTDROOF and scroll down, such an antenna will probably give you better results than your poor "doublet" and will still be "stealth" (note: scrolling further down the page you'll also find the design for the 16:1 BalUn to use with those terminated antennas)

btw, you remain the same, you are not pushing yourself "up"; the idea remains the same, up to you  changing if you can and want, otherwise...maybe someone will notice the way you behave, and good luck then.

[p.larner]

i removed the 4-1 balun but kept the 1-1,also made the feeder about 3ft longer,it seems ok now 73.

[A.Z.]

i removed the 4-1 balun but kept the 1-1,also made the feeder about 3ft longer,it seems ok now 73.

well, finally you took a good step, now... plug the vna after the 1:1 and sweep the antenna to obtain the impedance curve, at that point, having such infos it will be possible to find out if an impedance transformer may help, in such a case the connection will be antenna (balanced line), N:1 transformer, 1:1 balun/choke, coax to shack, ATU, TRX

The idea is to reduce the impedance mismatch using the transformer and balance currents with the balun/choke so that there will be less losses along the coax and little CMC, at that point the ATU will correct the mismatch and make the RTX happy; if you want you may add two further chokes, one at the ATU antenna input and a second one between the ATU and the RTX