Nagoya NA-7x1G antenna length

[nuz3k]

New to GMRS, and I have a question about the Nagoya antennas. The NA-771G is listed as 15.3 inches long and 1/2 wavelength. The NA-701G as 5.5 inches for 1/4 wavelength. Those numbers don't add up - the 771G ought to be double the length of the 701G, but it's nearly triple. And neither of those match up with the 462MHz wavelength of ~2 feet (right?). What gives? Is this just the result of the antennas being tuned for SWR experimentally, rather than by the theory? I could believe that for the 701G, since I gather that you may need to include part of the radio itself, but that'd make the 771G even longer. 

I received a knockoff from Retevis with a pair of their radios, and I'm wondering whether and how much I should trim it. It's about 14 1/4 inches long. I don't have an SWR meter or anything to dial in the length as I go.

[nuz3k]

Oh, is the NA-771G actually a 5/8 wave antenna? 

[BoxCar]

I wouldn't touch the antenna without either an antenna analyzer or SWR meter. The listed measurements usually include the antenna base and that isn't part of the actual radiating portion of the antenna. Going by overall length and cutting one antenna from a different serie to match is a really poor way ofdetermining the proper length.

[n4gix]

It's important to keep in mind that rubber duck antennas are actually a coiled wire, and not a straight length of wire. Because of this, attempting to "trim for best SWR" is not really possible.

[serrasalmus]

im using the 771g and its been working great for me

[Lscott]

6 hours ago, BoxCar said:

I wouldn't touch the antenna without either an antenna analyzer or SWR meter. The listed measurements usually include the antenna base and that isn't part of the actual radiating portion of the antenna. Going by overall length and cutting one antenna from a different serie to match is a really poor way ofdetermining the proper length.

Not only that but the metal sub-chassis of the radio along with your hand/arm combo forms part of the ground plane.

https://www.hamradio.me/antennas/ht-antenna-comparisons.html

I've tried checking the SWR on a bunch of HT antennas, well the results are mixed. I got widely varying results depending on how the antenna was mounted, directly to the analyzer - SMA type magnet mount on a ground plane (yes I found one at a swap) etc.

About the only ones you can reliability check are 1/2 wave types since they don't require a ground plane. I've seen a few for the Ham 2M band. I don't recall seeing anything for UHF.

https://www.smileyantenna.com/product-p/14686.htm

 

[nuz3k]

Risks of trimming the antenna have been noted. But n4gix it's a clone of the Nagoa, like I said, not the radio's stock rubber ducky.

 

Anyone have insight into the length of the NA-771 and NA-701, though?

[axorlov]

Insight into HT antennas is simple:

- measuring length is meaningless; however, in general, the longer the better;
- measuring SWR is meaningless;
- to measure the efficiency of HT antenna you must use field strength meter and calibrated human body + calibrated human hand.

[GuySagi]

My wife keeps threatening to send me back to the doctor to get my body recalibrated. I thought she was kidding until I read this thread.

I apologize because without consistency in testing the results are meaningless. So your term's precise and correct.  I do however, hope my note gifts you a chuckle today. Not many of those going around these days. 

[axorlov]

Hey, go recalibrate your body! Health is first, family is second, and everything else (including posting on silly forums) is a distant 100th.