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I've been having fun designing and building VHF antennas. My most recent build is a 3-element yagi fed with coax. I have a stub match at the feed point but no balun, just snap-on chokes. The PVC boom is starting to sag, so I'm planning to replace it and am taking the opportunity to make some design improvements.

I'm wondering whether a balun would be worth the extra time/effort if my primary goal is to increase the antenna efficiency. I can use matching networks to reduce SWR, but if the system is unbalanced, even a perfectly matched system will have losses from the common mode current in the coax shield. And if a balun would have a noticeable effect, what are the considerations are for different types of baluns? Common wisdom seems to suggest sleeve baluns for VHF, although that creates some challenges in positioning the coax relative to the yagi elements. I have also read that gamma matches can function as a balun. So how important is a balun for a VHF yagi? What are the considerations in choosing between sleeve balun and gamma match? Are there other options I should consider?

This is a question about power dissipated due to radiation and ohmic heating caused by common mode current in the coaxial shielding, specifically at VHF frequencies.

When a balanced antenna (such as a yagi) is fed with unbalanced feed line (such as coax), common mode current is induced in the shield of the coax. Even with a perfect SWR (no power reflected to transmitter) common mode current results in some of the power delivered to the antenna being radiated by or dissipated in the coax shield, rather than the antenna, reducing the power radiated by the antenna itself.

My question is: in practice, for VHF frequencies, are these losses due to common mode current negligible or can using a balun noticeably decrease losses due to common mode current? For the sake of this discussion, assume a near-perfect SWR (e.g., 1:1.01).

If there is an antenna efficiency reason to use a balun, what are the pros and cons of sleeve baluns vs gamma matches vs other types?

I've been having fun designing and building VHF antennas. My most recent build is a 3-element yagi fed with coax. I have a stub match at the feed point but no balun, just snap-on chokes. The PVC boom is starting to sag, so I'm planning to replace it and am taking the opportunity to make some design improvements.

I'm wondering whether a balun would be worth the extra time/effort if my primary goal is to increase the antenna efficiency. And if so, what the considerations are for different types of baluns. Common wisdom seems to suggest sleeve baluns for VHF, although that creates some challenges in positioning the coax relative to the yagi elements. I have also read that gamma matches can function as a balun. So how important is a balun for a VHF yagi? What are the considerations in choosing between sleeve balun and gamma match? Are there other options I should consider?

I've been having fun designing and building VHF antennas. My most recent build is a 3-element yagi fed with coax. I have a stub match at the feed point but no balun, just snap-on chokes. The PVC boom is starting to sag, so I'm planning to replace it and am taking the opportunity to make some design improvements.

I'm wondering whether a balun would be worth the extra time/effort if my primary goal is to increase the antenna efficiency. I can use matching networks to reduce SWR, but if the system is unbalanced, even a perfectly matched system will have losses from the common mode current in the coax shield. And if a balun would have a noticeable effect, what are the considerations are for different types of baluns? Common wisdom seems to suggest sleeve baluns for VHF, although that creates some challenges in positioning the coax relative to the yagi elements. I have also read that gamma matches can function as a balun. So how important is a balun for a VHF yagi? What are the considerations in choosing between sleeve balun and gamma match? Are there other options I should consider?