Jump to content
  • 0

Nagoya NA-7x1G antenna length


nuz3k
 Share

Question

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.

Link to comment
Share on other sites

9 answers to this question

Recommended Posts

  • 0

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.

Link to comment
Share on other sites

  • 0

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.

Link to comment
Share on other sites

  • 0
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

 

Link to comment
Share on other sites

  • 0

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?

Link to comment
Share on other sites

  • 0

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.

Link to comment
Share on other sites

  • 0

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. 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Answer this question...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use and Guidelines.