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Author Topic: 2M Yagi  (Read 4918 times)
YANS
Member

Posts: 9




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« on: February 23, 2001, 01:36:46 PM »

I am very new to ham so forgive this simple question.

I want plans for a yagi that will be easy for a new Tech. to build.

Can anyone help me out? Please remember not too technical.
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« Reply #1 on: February 23, 2001, 05:57:09 PM »

Glad to have you join us !

Here are some links for you to
view:

http://www.qth.com/antenna/
this one has lots of info

http://www.cebik.com
more technical but explained
so anyone can follow along.

let us know what you are up to
and how it works for you.

73 yuri
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« Reply #2 on: February 23, 2001, 05:59:30 PM »

http://www.softcom.net/users/kd6dks/quad.html

is another link but for quad beam
easy to build, low cost, big performer !

73
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YANS
Member

Posts: 9




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« Reply #3 on: February 24, 2001, 07:53:45 AM »

Well what this is to be used for is a VERY remote area of Maine. The unit needs to be able to be portable and after it is built, then the fun part begins.

I will need to figure out how to make it "break" down or fold up when not in use. It will also need to set itself in a "holster" of pvc pipe on the side of my pack thats why the Breaking down is needed. I just figure that I will get better range to the repeaters with this unit because I am allways carrying my compass, Topo maps, and GPS system.

I will be able to post this here after it is built, and its preformance.
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KG4DED
Member

Posts: 17




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« Reply #4 on: February 25, 2001, 12:15:23 PM »

I have the plans for a Yagi made from a Radio Shack FM antenna.  This thing is a piece of cake to make and it works very well.  It also folds and can be stored nicely.

If you would like the plans, email me and I will send them back.

Steven
kg4ded@hotmail.com
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WB6BYU
Member

Posts: 13168




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« Reply #5 on: February 26, 2001, 11:55:36 AM »

I designed a 2m antenna for just this purpose:  the boom is
1/2" PVC about 42" long, and the elements slip inside of
it.  The feedline attaches with alligator clips.  Simple and cheap
to make.  I'll dig out the dimensions and post them here.

However, having since travelled internationally with 2m directional
antennas, I would suggest the "tape measure" yagi from WB2HOL.
http://home.att.net/~jleggio/projects/rdf/tape_bm.htm
The antenna comes apart (if you don't glue the pipe joints) and the
elements can be rolled up and secured with a rubber band.

Good luck, and happy hiking! . . . - Dale WB6BYU
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WB6BYU
Member

Posts: 13168




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« Reply #6 on: February 26, 2001, 11:56:55 AM »

I designed a 2m antenna for just this purpose:  the boom is
1/2" PVC about 42" long, and the elements slip inside of
it.  The feedline attaches with alligator clips.  Simple and cheap
to make.  I'll dig out the dimensions and post them here.

However, having since travelled internationally with 2m directional
antennas, I would suggest the "tape measure" yagi from WB2HOL.
http://home.att.net/~jleggio/projects/rdf/tape_bm.htm
The antenna comes apart (if you don't glue the pipe joints) and the
elements can be rolled up and secured with a rubber band.

Good luck, and happy hiking! . . . - Dale WB6BYU
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WB6BYU
Member

Posts: 13168




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« Reply #7 on: March 01, 2001, 11:53:37 AM »

Here are the dimensions for the fold-up 2m yagi that I designed
several years ago.

The elements are made from #8 (3mm) aluminum wire.  Radio Shack
sells a 40' (12m) roll of "ground wire" which will make 4 antennas.
I've also seen plastic covered solid aluminum wire sold for
clotheslines which is stiffer (but take the plastic insulation off of it
first.)

Reflector:  40"  (101.6cm)
Driven element:  38.5" (97.8cm)
Director:  37.25"  (94.6cm)
Spacing:  16" (41cm)

The boom is 40" (102cm) of nominal 1/2" PVC thinwall water pipe
(actually about 200mm OD).  Drill holes through the pipe for each
element, starting near one end.  (This leaves some room on the
other end for a handle.)  Insert the elements through the holes, and
wrap a small piece of tape around each one above the boom to
keep it centered.  If you color code the holes and ends of the
elements it is easier to assemble in a hurry, without worrying if you
got the right element in the right place.

To disassemble, slip the elements out of the holes and insert them
into the boom length wise.  Put a pipe cap on each end, and you
are ready to go.

Feedline:  I use a delta match with a pair of alligator clips to hook
the feedline to the driven element.  Make a half wave coax balun
(using 32" or 81.3cm of foam coax, or 26.5" / 67.3cm of solid
dielectric coax).  On each end of the balun, attach a 7" (18cm)
length of hookup wire with an alligator clip on the far end.  These
clip to the driven element about 2" (5cm) each side of the boom.
Adjust the clip location for best SWR, then mark the element so you
can find the same point again.

If you aren't used to making a coax balun, it is simple.  Strip back
the insulation and braid from a piece of coax so the remaining
length is as specified.  Fold the coax in a loop and solder the two
ends of the braid together.  The two ends of the center conductor
are the outputs of the balun.  The feedline connects to either end
output of the balun and the common ground.

The resulting package is about 42" (107cm) long, which I find a bit
awkward for backpacking if there are any overhead branches.  
I have experimented with hinging the elements by bending an eye
on the end and connecting them with a bolt.  (Use a nut with a fiber
insert to keep the bolt from unscrewing as you work the elements.)
Arrange the joint so it acts as the stop to keep the element from
passing all the way through the boom.  With this approach, you can
get the element lengths down to about 22" (56cm).  I found that I
couldn't insert all 3 elements into one section of pipe because of
the size of the hinge joints, but it worked to put two in from one end
and one from the other end.  The boom can then be made from two
nesting sizes of PVC with a reducing coupler to join them.

If you want more gain, you can try 5 elements:
Reflector:  39.5" (100.3cm)
Driver:  37.75" (95.9cm)
Director (3): 36.5" (92.7cm)
Spacing: 16" (41cm)

You will probably want to use two sections for the boom.

One last suggestion to try:  the "string beam".
Use the same elements, but with string for the boom.  Take two
strings and tie them together at one end.  About 3' (1m) from the
end, tie the strings to the first element at about the 1/3 points on
the element.  Continue with the other elements.  It is convenient
to add a nice handle (PVC or wood?) tied to both strings behind
the reflector.

To use, tie the end of the strings to a convenient tree branch or
other support.  Grab the handle and pull the strings taunt.  The
yagi should snap into shape.  Works great if you have a support
available for the front strings.  (The longest antenna I've seen
built this way had over 40 elements and was over 60' / 20m long!)

Happy hiking! - Dale WB6BYU

PS:  I still think the tape measure yagi is a better choice!
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KF6WCH
Member

Posts: 5




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« Reply #8 on: March 01, 2001, 04:50:55 PM »

If you wanted to build a dualband 2m/70cm beam, which could be useful for working satellites while you are hiking, you might want to look at:

http://xe1mex.gq.nu/antenas/yagi.html

and this site, which describes a duplexer so you can use both antennas with one radio:
http://members.home.net/k0lee/duplexer.htm

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KD5LSX
Member

Posts: 3




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« Reply #9 on: March 15, 2001, 03:01:40 PM »

Check out http://www.qsl.net/kc5pyg/yagi

I've listed data and radiation patterns for the the different versions. I have built one for 2m and one for 70 cm. They are VERY esy to construct (30 min to 2 hours depending on skill level.



73 and good luck

Joshua - KD5LSX
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W2AEW
Member

Posts: 638


WWW

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« Reply #10 on: March 20, 2001, 10:32:28 AM »

Check out QST, July or August 1999 (can't remember the exact month).  There's an article that describes how to take a $20 FM Broadcast receiving antenna from Radio Shack and convert it to a 5-element 2m yagi.  Works great!
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