Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Converting a 5 element 6 meter beam to 2 meters  (Read 616 times)
N8DV
Member

Posts: 60




Ignore
« on: October 29, 2009, 08:36:19 AM »

Hi all, I have a new Cushcraft 5 element 6 meter beam that I thought would get used more than it is. It might sound crazy, has anyone converted such a beam for 2 meter use? With all the antenna experimenters out there, I thought I would give it a try.

73, Fred
Logged
K3WACKY
Member

Posts: 59




Ignore
« Reply #1 on: October 29, 2009, 10:13:20 AM »

Hi Fred,

I'd pack up the 6m antenna and store it rather than destroy it for 2 meters. You could build a 2 meter beam for very cheap using an old TV antenna or some stiff wire and PVC or wood for the boom.

(There was an article in a ham magazine or a web site for converting a TV antenna for 2 meters)

73
Logged
KM3F
Member

Posts: 499




Ignore
« Reply #2 on: October 29, 2009, 10:49:01 AM »

Sure you can but I think it's foolish to do it.
Sell the beam and buy a 2m unit with more gain than you would get by converting and staying 5 elements.
To make a conversion, the elments need to be shortened, spacing changed and a smaller gamma match placed and tuned.  That's all there is to it besides the mechnical changes and effort.
Gamma match can be made from a small section of the element tubing you cut of an element.
Use 1/4' rod from the hardware store covered with two short pieces of plastic tubing  to seperate the rod from the internal surface of the gamma tubing and make a strap out of 1/2' wide alum to complete the gamma match.
Your boom length will have to be shortened or place more directors on the new configuration requireing you to fine a source of more tubing.
Get a detail of a beam that has already been built and copy it.
What is a gamma match?
A one turn resonant loop that is series tuned by adjusting the inductive and capacitive lengths, making the 1/2 wave driven element a part of the circuit so energy can be coupled to it and to provide a 50 ohm match to the feed line.
How to tune the beam!
Get a list of known measurements for each element and their spacing and make the settings.
Assemble the gamma.
Place antenns facing straight up to the sky, for inital adjustments.
place SWR bridge close to the antena in the feedline then power with about 5 watts.
WORK the gamma match adjustments for both the rod insertion distance and strap position until you get the SWR down to 1 to 1 over the frequency range you want to use.  It won't stay flat over the whole band.

Expect the match might change some when it's put up but check this on a temporary setup about 12 to 15 feet high and make final touchup on the gamma feed.
Don't do any of the setup near metal building.
Built a number of these and all worked very well for both 6 and 2 meters.
You can build close spaced or wide space. The wide spacing is prefered for more gain and  narrower beam pattern.
I would review antenna tech on beams to get an idea of what you are working with before you begin carving up a new 6m beam..
Good luck.
Logged
WB2WIK
Member

Posts: 20547




Ignore
« Reply #3 on: October 29, 2009, 02:12:02 PM »

Why not just add 2m elements to the same boom and then put it back up as a 2-band beam (with separate feedlines)?  That works fine and it's pretty easy to do.

This is really easy to do if you make the 2m elements loops, so you have a 2m quad and a 6m yagi on the same boom.  I've done that myself, no interaction or other drawbacks.
Logged
VE3FMC
Member

Posts: 983


WWW

Ignore
« Reply #4 on: November 13, 2009, 05:50:47 PM »

If you lived closer to me I would trade you a pair of 11 element two meter beams for that 6 meter beam.

Do not butcher that beam!

Buy or build a 2 meter beam.
Logged
K2NRC
Member

Posts: 19




Ignore
« Reply #5 on: November 15, 2009, 09:42:17 AM »

'This is really easy to do if you make the 2m elements loops, so you have a 2m quad and a 6m yagi on the same boom. I've done that myself, no interaction or other drawbacks'-

does the aluminum boom interfere with the small diameter of the 2m loops?  have 3-6m yagis, a vb64dx hy gain, mfj 1762 & a homemade with solid aluminum rod on angle aluminum boom 'a la' the ebay specials.  was thinking about an m2 7 element 2m yagi, but, your suggestion makes a 6-8 element 2m quad mounted on either the hy gain or homemade (due to longer boom) a possibility.....if the interaction of the boom is a non-factor.
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!