Hairpin matching

[Mr Clean]

I have found a hairpin match that is suppose to be a better match at 50 ohms vrs about 25 ohms for a gamma on a yagi. DX engeneering has them and I know they make great stuff. I guess my question is would this work better on a 5 element Maco than the stock gamma. I am thinking yes and for 25 dollars apeice not much of an invesment. what do the antenna gurus on the forum think?

 

[FL Native]

well im no guru. but yes hairpin is way better. gama has way more loss than a hairpin match.

good choice on the dxengineering they make great stuff. 8)

 

[Master Chief]

The "beta" match (also called "hairpin" for patent reasons) was originally designed by Hygain. It is an awesome way to feed an antenna.

You can set up your Maco antenna with this matching system IF you isolate the driven element from the boom.

You will need to buy DX Engineering's "DXE-BEB-2" boom to element bracket to fit Maco's 2" boom.

You will also need to cut the 5/8 element in half and add 6" of 3/4" x .058 tubing and 4" of 7/8" x .058 to the ends and drill to install on the BEB-2.

Jay's Crusader beam is using this type of feedpoint also......but with a special current balun (not shown on this prototype).

 

[Captain Kilowatt]

When I built my six element yagi for 6m I first tried a gamma match. It was a real pain to get set and the pattern was skewed quite a bit. I dropped the beam and converted to a hairpin match and had it tuned up in about 1/2 hour.I fed it with the standard 1/2 wave coaxial balun arrangement and have had great success with it. The pattern is much cleaner and tighter than with the gamma feed.As for reduced losses I can't say as I have no real way to make before/after comparisions but I do know the antenna is one hot performer.

 

[W5LZ]

A gamma match is asymmetrical, a beta match is symmetrical. The beta will 'help' with pattern 'skewing'. The loss between the two isn't enough to make much practical, if any, difference in what's radiated. The mechanics of the two types of matching devices is not the same, so some modification is necessary if you change (in either direction). ... Or if you really want to have some fun, change to a folded dipole, feed it with parallel feed lines, build 'slip-rings' for the turning part, and then through a tuner. Who cares what the impedances are, doesn't matter.
- 'Doc

 

[KD7UGY]

I built everything for my driven element and hairpin match on my yagi in a couple hours, but I'm a machinist with a full machine shop at my disposal. I was very impressed with how well the whole thing tuned in when I got it done. I used the computer modeling program I got with my ARRL Antenna Book and when I got everything put up it took very little adjusting to get tuned in perfect. It would have worked without doing the fine tuning but I'm a perfectionist when it comes to tuning antennas.

 

[Mr Clean]

The "beta" match (also called "hairpin" for patent reasons) was originally designed by Hygain. It is an awesome way to feed an antenna.

You can set up your Maco antenna with this matching system IF you isolate the driven element from the boom.

You will need to buy DX Engineering's "DXE-BEB-2" boom to element bracket to fit Maco's 2" boom.

You will also need to cut the 5/8 element in half and add 6" of 3/4" x .058 tubing and 4" of 7/8" x .058 to the ends and drill to install on the BEB-2.

Jay's Crusader beam is using this type of feedpoint also......but with a special current balun (not shown on this prototype).

I was reading on the DX site and it stated that if I insulate my driven element I would not have to change how long it is.Why would I MC.Not calling you wrong just want to make sure. Thanks for any info. Also would you use a balun?

 

[A7DX]

I have found a hairpin match that is suppose to be a better match at 50 ohms vrs about 25 ohms for a gamma on a yagi.

well im no guru. but yes hairpin is way better. gama has way more loss than a hairpin match.

It was a real pain to get set and the pattern was skewed quite a bit.

if so then your gamma match is/was improperly constructed and misconfigured.

 

[Captain Kilowatt]

It was a real pain to get set and the pattern was skewed quite a bit.

if so then your gamma match is/was improperly constructed and misconfigured.

If that was the case then there are an awful lot of improperly designed and constructed commercially build antennas out there.Pattern skewing is actually very common with gamma match fed antennas.The amount of skewing tends to become much more noticable the higher in frequency you go.

 

[A7DX]

there are an awful lot of improperly designed and constructed commercially build antennas out there.

no, just the gamma matches.

 

[Captain Kilowatt]

Don't hold back,please enlighten us as to why you think this is so.There are lots of referances to pattern skewing caused by feeding with a gamma match.The claim is that since a gamma match actually feeds the antenna away from the element center point,skewing occurs. Please explain how this can be overcome when using a gamma match.

 

[A7DX]

The claim is that since a gamma match actually feeds the antenna away from the element center point, skewing occurs.

i hadn't heard that. you have links?

 

[Captain Kilowatt]

This is for starters.

From Astronwireless

The Gamma match is an unbalanced feed system since power is only connected to one side of the driven dipole. This often causes radiation pattern distortion. Our Yagis feature balanced center-feed systems. This system is more complex than a Gamma match but, it is inherently more symmetrical because power is fed to both sides of the driven dipole. Furthermore, the AntennaFeed system is less affected by the placement of the transmission line. The result is a clean and distortion free symmetrical radiation pattern.

From DXengineering

The Gamma match is an unbalanced system that typically distorts the antenna pattern.

From Cebik's site

In VHF beams, many builders have noted and measured some pattern distortion with the gamma match. Hence, the Tee has almost become a standard for beams having other than a 50-Ohm feedpoint impedance. HF beam makers have more confidence in the gamma match, whose parts are a relatively smaller proportion of the driver structure than they are at VHF and UHF. However, the Tee is inherently balanced.

Now,care to comment why you believe otherwise. I would be interested in hearing more theory as to how the shortcomings of a gamma match can be overcome.

 

[W5LZ]

QRN,
This is being 'picky', but might clear up some misconceptions.
From "Astronwireless"s quote, power is being fed to both sides of the driven element. One side isn't directly connected, but through a capacitor/capacitive network. It still gets to that 'other' side.
The amount of skew of the radiation pattern is not a major thingy unless you are direction-finding. It's also not a 'fixed' amount, varys from antenna to antenna and environment. (Some environments, installations, introduce some skew all by them selves.) In most cases the amount of skew just isn't very critical at all, and can be compensated for if your 'numbers' just have to be 'dead nuts' accurate. Until you get into the VHF/UHF regions that skew is a very small portion of a directional antenna's beam width. At HF, it's probably less than the accuracy margin of the rotor control's indicator. (If it ain't, you'd better find another compass - lol.)
For typical HF use a gamma match isn't a bad deal at all. Sure it has 'qwerks' you should be aware of, but in the majority of cases, that 'awareness' is all that's required. If you wanna change from a gamma to a beta match, be my guest! If you don't want to, no biggy with that either. If you're into microwaves, radar, and such, dump the gamma match. Or, do some calibrating.
- 'Doc

 

[Mr Clean]

When I said I found a gamma matches at 25 ohms and a hairpin at 50 ohms what I should have said was I saw in a book. I found the info in a book A7DX. I am just trying to learn. Peace