Jump to content

GMRS Repeater Antenna


WRVY769

Recommended Posts

3 minutes ago, WRVY769 said:

what is some of the other variables. sorry I don't know very much about dB gain and antenna. 

So a 12 dB gain is simply more focused in some directions. As an example it might not hear signals that are above, below, or to the sides or rear of it, while a 6 dB antenna is usually more receptive throughout a wider swath. Study the propagation patterns of the antennas you’re looking at. 
Many commercial antennas have less gain in order to be less directional. 

Link to comment
Share on other sites

9 minutes ago, WRVY769 said:

this is the antenna. it's a vertical is there a way to direct the patterns in one direction. 

Comet Antennas GP-9NCA Comet GP-9NCA GMRS/FRS-Commercial Dual Band VHF/UHF Base Vertical Antennas | DX Engineering

No, that’s a different type of antenna. The most common antenna used to direct RF in a given direction is called a Yagi-Uda antenna. 
That’s a good antenna though. But as some reviewers point out it has a fairly flat pattern. 
https://www.eham.net/reviews/view-product?id=2455

Link to comment
Share on other sites

 

16 hours ago, WRVY769 said:

what does it mean by is has fairly flat pattern? 

Ignore the frequency and free-space titles (though the first IS a halfwave in free space)

image.png.7caac16beb3a765013ced3a7fd3a665b.png

This is the pattern of a half-wave dipole in free space. It has 2.16 dB gain over an isotropic emitter.

image.png.51613e8f3a1a37b751b79d9179ec67b3.pngimage.png.4fd6e739e17e0cc9d3a730be6f06a1cf.png

These are over (as I recall -- old images) "perfect ground" at two different heights. Note the reduced gain.

A high gain vertical antenna will squeeze those patterns into much narrower "beams". Depending upon how high  it is mounted, and surrounding terrain, your narrow high-gain beam may just be hitting lots of trees and hills, while a lower gain might go a bit above said terrain.

image.png.b4644a65c1175ed64fdfc6f7f6fec8f3.png

This is an antenna over "real ground" -- note the near 7dBi gain, but also note the elevation angle it occurs at.

 

Link to comment
Share on other sites

  • 1 month later...

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
Reply to this topic...

×   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.

×
×
  • Create New...

Important Information

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