Yagi tuning question

[jrs71]

I have a 3-element yagi that will be used for receive only. It is currently tuned at about 149 MHz. Most of what I will be listening to will be in the 155 MHz area and a couple at 160MHz. Would it perceptibly improve reception if I trimmed the elements for 155 MHz?

Thanks, this stuff is new to me and I appreciate your help.

 

[Josh]

no, it shouldn't matter. Yagis are fairly wide-band as it is.

But shoot, 6Mhz is nothing... if you were to try listening to low-band or something with it, you may have a problem.

-Josh

 

[VernM]

You would be shortening the elements about an inch. But, with a Yagi, the space between elements also would shorten slightly too. In practice, you won't hardly notice the difference.

 

[RISC777]

I have a 3-element yagi that will be used for receive only. It is currently tuned at about 149 MHz. Most of what I will be listening to will be in the 155 MHz area and a couple at 160MHz. Would it perceptibly improve reception if I trimmed the elements for 155 MHz?

Thanks, this stuff is new to me and I appreciate your help.

Didn't you get with the antenna a sheet detailing what lengths to field tune it by?
If not, check the mfr.'s web site for one.

But as already said, you may not notice much difference if you did change the tuning.

 

[kb2vxa]

Hi JRS and all,

DON'T mess with the elements, without careful calculation of length and spacing it's SO easy to mess it up! Then too there's some drilling and blasting involved. More important is the gamma match, you can easily tune it using an MFJ or equivelent antenna analyzer, they usually go up to 170MHz or so. Don't overlook the fact that an odd length of coax will mess up the readings, antennas are ALWAYS tuned AT the antenna whether an analyzer or SWR meter is used. A VHF antenna doesn't need to be far off the ground to avoid it's effects, standing atop a wooden step ladder away from obstructions will do it, point it straight up just to make sure.

If you're not into a lot of antenna experimentation it's not worth the high cost of an analyzer, you can borrow one from a local ham or have him tune the antenna for you. Not all of us have them but likely someone in a local club does.

 

[jrs71]

Thanks all for the the advice and education. Think I'll just leave it as it came from the factory. I do have a spec sheet and could easily trim the elements to length but I'm afraid changing the spacing could present structural problems to the boom.