Changing design frequency of K2RIW 432 MHz yagi
 

I need to "move" a 19-element K2RIW 432 MHz yagi from its orignal
design frequency of 432 MHz to 445 MHz. I can't change to element
positions but I can change their lengths. But by how much? -W9IP

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I need to "move" a 19-element K2RIW 432 MHz yagi from its orignal
design frequency of 432 MHz to 445 MHz. I can't change to element
positions but I can change their lengths. But by how much? -W9IP


That is a 3% change. Shorter. Check the VSWR to see what BW you are
getting. You maybe able to cut the driven element slightly, or just change
the postion of the gamma match. Since the rest of the antenna can't change
the element positions the antenna is stuck at 432 with the BW it has, which
may include 445. 3% is a small change, within mechanical tolerances, and the
gamma match may define where the best VSWR is.

Thanks - I wasn't too worried about the SWR node, but rather the gain
peak. I figured that I could shave off a millimeter or two (or three?)
from each element to raise the frequency of maximum gain. Not having
any yagi-modeling software, it wasn't clear to me what would happen.
Maybe it's not worth the effort.

Thanks - I wasn't too worried about the SWR node, but rather the gain
peak. I figured that I could shave off a millimeter or two (or three?)
from each element to raise the frequency of maximum gain. Not having
any yagi-modeling software, it wasn't clear to me what would happen.
Maybe it's not worth the effort.

Thanks - I wasn't too worried about the SWR node, but rather the gain
peak. I figured that I could shave off a millimeter or two (or three?)
from each element to raise the frequency of maximum gain. Not having
any yagi-modeling software, it wasn't clear to me what would happen.
Maybe it's not worth the effort.


There is information about 'frequency-shifting' yagis in my VHF/UHF Long
Yagi Workshop pages, and links to software to help you do it.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Ian - Perfect! Just what I was looking for (Why didn't I find this
treasure trove with Google?)

wrote:
Ian - Perfect! Just what I was looking for

You're welcome, Mike.

(Why didn't I find this
treasure trove with Google?)

Thanks for letting me know that. I've added a few more keywords to the
page, which should help in future.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek