1:1 Current Balun by N5ESE
Here's another handy little Altoids QRP project. For Field Day 2002, I wanted to use my new Elecraft K1 (which has an automatic antenna tuner built-in) to feed a full-wave loop on 40 meters, to use on all bands 40 - 15. To preserve the feedline balance (I used 300-ohm ladder line), I needed a balun at the output of the K1's antenna tuner. This 1:1 balun did the trick quite nicely.
http://www.n5ese.com/balun_1-1.htm

1:1 Guanella Current Balun by VK6YSF
Requiring a balun to feed a balanced feed line with an un-balanced T-Match tuner, a 1:1 Guanella Current balun design using a L15 ferrite toroid core was selected among others.
http://vk6ysf.com/balun_guanella_current_1-1.htm

1:1 Ruthroff voltage balun by VK6YSF
Requiring a balun to feed a balanced feed line with an un-balanced T-Match network a 1:1 Ruthroff voltage balun design using a T200-2 Toroid core was selected.
http://vk6ysf.com/balun_1-1.htm

1:1 Voltage Balun for HF wire dipoles by MØUKD
Heres a neat 1:1 50 ohm balun for use on HF horizontal wire dipoles. It uses an AM radio ferrite rod, with 3×14 turns of wire. 10-14 turns should be good for 2-30MHz. I used 18SWG enammeled copper wire. It all fits in a small project box.
http://m0ukd.com/homebrew/baluns-and-ununs/11-voltage-balun-for-hf-wire-dipoles/

1:4 Current Balun by N5ESE
Here's yet another handy little Altoids QRP project. This makes a great travel companion to the 1:1 current balun (described -here-), and is intended to aid in tuning a balanced antenna or feedline that has a high impedance (100-600 ohms).
http://www.n5ese.com/balun_1-4.htm

1:4 Guanella Current Balun by VK6YSF
Requiring a balun to feed a balanced feed line from an un-balanced T-Match tuner, a 1:4 Guanella Current balun design using two L15 ferrite toroid cores was selected among other balun types.
http://vk6ysf.com/balun_guanella_current_1-4.htm

20/11/10m.monoband end fed halfwave antenna by PD7MAA
The vertical end fed half wave antenna is my choice for it’s easy to employ and it's a perfect DX antenna . This antenna is grounded thus giving les static noise to your receiver.
http://pa-11019.blogspot.com/2011/06/20m-endfed-halfwave-antenna.html

4:1 Ruthroff voltage balun by VK6YSF
Requiring a balun to feed a balanced feed line with an un-balanced T-Match network a 4:1 Ruthroff voltage balun design using a T200-2 Toroid core was selected.
http://vk6ysf.com/balun_4-1.htm

6:1 Ruthroff voltage balun by VK6YSF
Requiring a balun to feed a balanced antenna from an un-balanced load with a impedance step up from 50ohms to 300ohms, a 1:6 Voltage balun design using two L15 ferrite toroid cores was selected.
http://vk6ysf.com/balun_6-1.htm

9:1 Magnetic Longwire Balun / Unun by MØUKD
These are sometimes known as a Magnetic Longwire Balun. Its really an impedance transformer (9:1) to feed a high impedance, end fed (unbalanced) random wire which is likely to be a few hundred ohms, and transform it into something closer to a 50Ω (unbalanced) coaxial input, hence UnUn.
http://m0ukd.com/homebrew/baluns-and-ununs/91-magnetic-longwire-balun-unun/

9:1 voltage unun using a L15 ferrite core by VK6YSF
With the view to establish a quick and easy multi-band antenna deployment for portable and camping operations a simple long wire antenna with an earth or earth plus counterpoise arrangement with a 9:1 voltage unun is one possible solution.
http://vk6ysf.com/unun_9-1_v2.htm

9:1 voltage unun using a T-200-2 powdered iron toroid core by VK6YSF
With the view to establish a quick and easy multi-band antenna deployment for portable and camping operations a simple long wire antenna with an earth or earth plus counterpoise arrangement with a 9:1 voltage unun is one possible solution.
http://vk6ysf.com/unun_9-1.htm

Air Cored 1:1 Balun for 3.5 – 30.0 MHz by G8ODE
Photograph showing the COMFORT™ top cap with the 4mm screw terminals attached and the MARLEY™ Trap Adjuster end cap with the SO239 connector attached to the former with the trifilar winding. Flexible wires are attached to the 4mm screw terminals and soldered to the windings A & C ends.
https://rsars.files.wordpress.com/2013/01/air-cored-1-1-balun-for-3-5-30-0-mhz-1-31.pdf

Balun 1:4 (For Folded Dipoles or Wireman-feeding) by DK7ZB
With 2 x 8 turns bifilar (PTFE-cable) this balun on a FT240-43 handles 1 KW. For better impedance matching a parallel capacitor 12 pF/1 KV for the coax input is recommended. here are 4 x 12 pF/500 V used.
https://www.qsl.net/dk7zb/Baluns/balun_1-4.htm

Broadband-Balun 1:1 for open-wire-feeding with undefined impedance for a wide range by DK7ZB
16 bifilar turns on FT240-43 for high power up to 700 Watts.
For unsymmetrical ATUs to symmetrical open wire feeding.
https://www.qsl.net/dk7zb/Baluns/broadband.htm

Build your own HF balun by EA4EOZ
A balun is a MUST for dipoles or similar antennas when they are feed with coaxial cables. Many hams connect the center conductor of the coaxial cable to one side of the dipole, and the shield to the other. Wrong!
http://ea4eoz.blogspot.it/2012/09/build-your-own-hf-balun.html

Coax Choke Balun Designs by G8ODE
The two coaxial Choke BALUNS are constructed from 40mm plastic drain pipe using 8-10 turns of Mil Spec RG58 or MIN-8 Coax (approx 2metres) The bottom end coax is held in place with a small plastic tie-wrap. A plastic cap from a food jar is used as at the top of the BALUN.
https://rsars.files.wordpress.com/2013/01/choke-balun-designs-g8ode-iss-1-31.pdf

Dual Ratio 1:1 & 4:1 Balun for 3.5 – 30.0 MHz by DB6NT
This balun has been used at 100watts with a full-sized G5RV, Windom and 40m & 20m vertical antennas. It is essential that the Amidon™ toroid is housed in a watertight box, such as an IP56 Rated box.
https://rsars.files.wordpress.com/2013/01/dual-ratio-1-1-4-1-balun-for-3-5-30-0-mhz-1-31.pdf

End Fed Half Wave Antenna Coupler (EFHW) by MØUKD
I have been experimenting with feeding end fed half wave antennas matched by a parallel tuned circuit coupler. This article will explain my findings and reasons for constructing it the way I did.
http://m0ukd.com/homebrew/baluns-and-ununs/end-fed-half-wave-antenna-tuned-coupler-efhw/

HF 1:4 balun by PA3HCM
The first HF antenna I wanted to build was a Windom Antenna. This antenna required a 1:4 balun, so I made one.
http://www.pa3hcm.nl/?p=305#more-305

Homemade HF Antenna Balun by AA5TB
A balun is a device that is used at the feedpoint of a balanced antenna when an unbalanced feedline is desired to feed the antenna. Balun is a contraction for BALanced to UNbalanced.
http://www.aa5tb.com/balun.html

QRP Balun by AA5TB
I had a high permeability ferrite rod and an old B&W dipole center insulator in my junk box so I decided to construct a choke type balun for QRP use.
http://www.aa5tb.com/qrp_balun.html

Windom baluns for kilowatt range by OH7SV
Windom balun made with Amidon ferrite toroids.
Windom balun made with surplus ferrite rods.
http://www.jumaradio.com/windom/windom-balun.html

Enhanced OCF Dipole Balun by OH7SV
All antennas need a common mode balun. Especially OCF dipole (sometimes called Windom) needs enough common mode reactance because the feeding point is "hot" - not in the zero RF. Here is an enhanced balun for OCF dipole.
http://www.jumaradio.com/enhanced-OCF-balun/enhanced-OCF-balun.html