What are gamma and hairpin matches?
The gamma match and hairpin (beta) match are geometric matching methods for driven elements of Yagis and dipoles whose impedance is below 50 Ω. A gamma match taps a rod from the coax center conductor onto the element some distance from its center, with a series capacitor to cancel the rod’s inductance; a hairpin match places a shunt inductive stub across a slightly shortened, capacitive split element, forming an L network.[1][2]
How does a gamma match work?
The element center is at zero RF voltage, so it can be connected directly to the boom and coax shield. Moving the tap outward increases the impedance seen, like a tapped autotransformer; the rod and element form a short transmission-line section whose inductance is cancelled by the series capacitor. It is unbalanced and can cause slight pattern skew.[1]
How does a hairpin match work?
Shortening the driven element makes its impedance R − jX with R below 50 Ω; a shunt inductance (the hairpin) across the terminals transforms it upward to 50 Ω, exactly an L network with the element’s capacitive reactance as the series arm. A balun is required because the element is balanced.[1]
What are T and delta matches?
The T match is a balanced double gamma; the delta match fans a balanced line out to tap points on the element. Both allow the element to be continuous at its center.[2]
Frequently asked questions
Is a gamma match lossy?
Losses are low if the capacitor is high-Q and contacts are good.
Why are Yagi driven elements low impedance?
Coupling to closely spaced parasitic elements lowers the radiation resistance.
Does a hairpin need a balun?
Yes, to feed a balanced split element from coax.
See also
References
Online sources accessed October 21, 2026; printed works cited by edition. See all sources.
- “The ARRL Antenna Book for Radio Communications”. ARRL. multiple editions.
- “Antennas for All Applications, 3rd ed.”. J. D. Kraus and R. J. Marhefka, McGraw-Hill. 2002.