Best way to feed a hairpin beta match

[Mr Fix it]

This is the way to go when it comes to feeding a yagi with a hairpin beta match. It forces each side of the driven element to have an equal amount of current. It also eliminates a skew in your pattern and also stops common mode current.

Custom 15kw plus 1.1 balun - Ham*Repair*Guy

 

[Captain Kilowatt]

This is easier and just as good (or better). It is a simple half wave transmission line delay cable that acts as a 4:1 balun which is what is usually needed on a multi-element yagi where the input impedance is low. The main transmission line connects to the middle unused jack.This is the feedpoint of my hairpin matched 6m yagi.

 

[Mr Fix it]

balun

Interesting I will have to give it a try.

 

[Captain Kilowatt]

Basic hookup. Make sure to take the cable's velocity factor into account when cutting the half wave of cable. I used the MF-269 antenna analyzer to measure mine.Note that the image shows the transmitter directly connected to the left terminal while I connected to the middle. This was just a simple matter of the way I wired the three jacks that resulted in symmetry along the antenna. Electrically the connections on my yagi are the same as in the image below.

Better images of the hook up.Note that the center jack and one other jack are connected together and are also connected to one element side. The other jack is connected directly to the other element side. The element is insulated from the boom while the three jacks are mounted on a piece of metal that is connected to the boom via the element mounting bracket so that the three ground connections are common yet isolated from the driven element thus preserving a balanced feedpoint.

 

[Shockwave]

This is easier and just as good (or better). It is a simple half wave transmission line delay cable that acts as a 4:1 balun which is what is usually needed on a multi-element yagi where the input impedance is low. The main transmission line connects to the middle unused jack.This is the feedpoint of my hairpin matched 6m yagi.

CK, I first found the balun you show in the 1959 Amateur Radio Handbook and never went back to other methods. It was highly recommended for VHF and up due to its extremely low loss. Just the loss in the half wave cable and this balun already does most of the impedance matching for you with the Yagi! Works great with the Hairpin or T match and is easily adaptable for HF operation.

This truly provides the desired symmetrical feeding of the driven element that puts the most energy into the elements and not the coax braid. Just looking at where Captain Kilowatt has his Hairpin tuned, I can tell the element is being feed balanced. Tapped directly in the center and not off to one side.

 

[HomerBB]

I used this matcher with a delta matched 2 element Yagi. I didn't have such a tidy setup, however. Looks great!

 

[Captain Kilowatt]

I went with three connectors to make things neater as well as make it easier to work on. I had to change out the balun cable (after about 20+ years) and it was simple to do. No soldering or special weatherproofing other than waterproofing the connectors which is easier than cut cable ends.

 

[HomerBB]

Clever. I would have had to do all the resoldering as mine was soldered within a box.

 

[Mr Fix it]

Interesting, I will have to build one of these and stick it in a nema box. I will post the pics on my site when its finished. Im building a yagi right now I will have to give both a try and see what I come up with. Thanks for the pictures and info captain kilowatt. And also for input from every one else. 73

 

[Captain Kilowatt]

What band is this for? The length stars to get a little long on 10m and lower. On HF you are better off with a toroid or air coil wire wound balun. I elected not to house it in a box of anykind simply because t was easy to weatherproof the connectors as it was.

 

[Mr Fix it]

Hi captain kilowatt. The match would be used on antennas built for hf bands. I have customers here in ct who I build and install antennas for some are cb guys and some are fellow ham ops .I just got home from a long day of putting one together then installing it on his tower. Was kinda scary since it started to lightning out pretty bad as I was sliding the mast to boom plate onto the rotor mast. I know it was stupid to continue under these conditions but I really wanted to get it finished.

I should add that the tower was cranked over and not vertical while I was doing this. I stood on a ladder while I mounted the antenna to the mast.

A couple guys here in ct use the same match you have in your picture on their t match cb antennas.They use the maco m104 as the base and modified it from there.

73

Scott

 

[Captain Kilowatt]

I see. Well 10/11m is not too bad as the length of cable needed is about 12 feet assuming a velocity factor of 66%. I am just not so sure I would want to use it any lower as I would prefer to use a good wire wound air core balun instead. I used a W2DU balun on my tribander and will use it again on my 12/17m dualbander. This is it pictured below when I took it apart after learning that some baluns are simply a piece of coax cable with ferrite beads installed on it inside a PVC enclosure. I was happy to find out mine was not one of those.