Hygain 28FM 2 meter coax balun (home-brewed)

[Alan Blackmon]

I bought a used 8 element 2 meter beam. I was replacing the corroded parts with nice shiny stainless steel parts. I looked at the downloaded assembly instructions and see where there is a coax bathing balun. I see a part number for this also. Well I have tons of coax both 50 ohm and 75 ohm. I suspect this balun is made from 75 ohm coax but the instructions say nothing about the length of it. I have figured out where to connect it and would prefer to build it rather than buy it.

Does anyone know the length of this coax matching balun for the antenna?

It appears someone added the connector. Instructions point out where to connect coax pigtails. You can see the connector points for the coax center conductor and shield in this photo. Each side of the hairpin is where I see the center conductor was connected. The shield is still connected and cut. Now all I need is how long do I make this coax balun?

Thanks

Alan KJ7EFC

 

[BJ radionut]

26.85 inches...I am thinking should work...

 

[BJ radionut]

871704 Balun Assembly, 2-meter

Above is the replacement part number...Drop HyGain an email...bet they would tell you...but still pretty sure that is a 4:1 balun.
My 6m beam with "Beta-Match" uses a similar set-up...just no hairpin
All the Best
Gary

 

[BJ radionut]

The 26-1/2" is the overall end-to-end length of the balun. It can be folded or coiled, doesn't matter. It's just a 1/2-wavelength delay line and the 26-1/2" is based on using coax with a solid dielectric like RG-58/U, RG-58A/U, RG-58C/U, RG-213/U etc. It's 324.72/f(MHz) = length in feet.

The balun is 1/2-wavelength, corrected for cable velocity factor.

FOUND here: https://forums.qrz.com/index.php?threads/hy-gain-vb-214fm-beam-antenna.546565/

the matching stub for 14 elements should be the same as the 8 (?)

 

[Justme]

Doing that balun, you measure from braid to braid end.

 

[Captain Kilowatt]

Correct Gary. It is a 4:1 half wave coaxial balun. The drive impedance tends to be quite low and that raises the impedance back up to something near 50 ohms. I installed three SO0239 jacks on my home brew 6m beam to make waterproofing easier. It is also easier if I need to replace the balun for any reason.This is mine. Coax feed to the shack connects to the middle jack.

 

[Alan Blackmon]

Thanks BJ radionut. (again my spell check wanted to make you radiant like so many years back when I joined the group) I did make the coax matching stub after more searching on what it was and the dimensions it needed to be cut but I hooked it up wrong. The PDF file from the internet was very hard to see the details of the hook up. With your supplied art work I can get the connections done right. Thanks so much. My antenna isn't a folded dipole but with the supplied photos from Captain Kilowatt is looks like this is the right connection to make on this antenna even if it isn't a folded dipole. The instructions do say the if I am going to feed the antenna with 50 ohm coax to use this for proper matching.

 

[Alan Blackmon]

Thanks Captain Kilowatt. I see the connection points here in your photos. Well I hope I do anyway. Back to my beam and get this done. Thanks for the help.

 

[Captain Kilowatt]

Thanks Captain Kilowatt. I see the connection points here in your photos. Well I hope I do anyway. Back to my beam and get this done. Thanks for the help.

My antenna does not have a folded driver element either and is a regular dipole split in the middle. Basically the main feedline connects directly to one side of the antenna directly as well as is jumpered to one end of the balun. The other end of the coaxial balun then connects directly to the other side of the element.