There's a model of HT antenna for the GMRS band by Nagoya (NA-771G) that's specified as a half wave. How can that be? An end fed half wave antenna needs a 49:1 impedance transformer to match with the transmitter? Is it more like a 5/8 or 3/4 wave in reality?


2 Answers 2


Judging by looks, it's a half-wave element with an autotransformer at the base. Nagoya says the antenna is 15.3 inches in length. Taking measurements from a photo, the bottom 2 inches is in that fat molded section that clearly contains some kind of coil (the autotransformer), and the remainder is a whip that's around 13" long, which is perfect to be a half-wave at ~460 MHz.

This kind of design is seen reasonably often in handheld and mobile antennas.

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    $\begingroup$ I have a half wave telescoping 2m antenna. Big fat coil at the bottom. And a great way to break your SMA off if you're not careful. $\endgroup$
    – user10489
    Commented Feb 16, 2023 at 23:46

It is worth noting that a vertical end-fed antenna is often used in conjunction with a ground plane that interacts strongly with the antenna to reduce its effective impedance to a value that the transmitter can drive directly, without any loading coil.

So, for example, the four drooping radials surrounding the vertical 1/4 wave "whip" of a 2-meter base station antenna let it match up well with a 52-ohm transmission line.


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