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Author Topic: yagi made with insulated wire  (Read 1074 times)
VE7RTB
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Posts: 5




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« on: April 14, 2010, 09:14:02 PM »

will antenna work?.
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WT0A
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Posts: 922




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« Reply #1 on: April 14, 2010, 10:14:26 PM »

maybe
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G3TXQ
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Posts: 1534




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« Reply #2 on: April 15, 2010, 12:48:26 AM »

You might need to adjust the dimensions - the insulation can shift the resonant frequency of an element by as much as 5%.

73,
Steve G3TXQ
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WA3SKN
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Posts: 5559




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« Reply #3 on: April 15, 2010, 05:22:46 AM »

Yes, it will work.
There are SO MANY other factors that are much more important in antenna design.  Insulation is really a non-issue from a practical standpoint.  
73s.

-Mike.
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KB1GTX
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Posts: 463




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« Reply #4 on: April 15, 2010, 05:40:01 AM »

What's the frequency?
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W4VR
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WWW

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« Reply #5 on: April 15, 2010, 07:13:58 AM »

I assume you're talking about an HF yagi.  I use insulated wires for some of my HF yagis and the insulation makes the wire electrically longer.  I put up the driven element, prune it for resonance, then cut my parasitic elements accordingly.  On 40 meters, for example, the insulation decreases the velocity factor by about 1.5% on half-wave elements.
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N3OX
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« Reply #6 on: April 15, 2010, 08:14:00 AM »

If you're using a carefully done antenna design that will "just work" if you build it accurately with the right size bare wire, it will be less work to strip the wire than to retune.

If you are willing to tweak and tune until it works right, or you don't actually care if it works right, then you can use insulated wire in place of bare wire.

You can always check it after the fact and see if the performance is acceptable. I personally wouldn't risk it since a few minutes with a pocketknife or a couple days wait for the right bare antenna wire from an online shop would be ok with me.

73
Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
AA4PB
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Posts: 13032




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« Reply #7 on: April 15, 2010, 08:31:17 AM »

Thinking about a 40M yagi, proximity to the ground (i.e. low height) is likely to cause more detuning of the elements than the insulation on the wires.
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WB6BYU
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Posts: 13580




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« Reply #8 on: April 15, 2010, 08:49:07 AM »

Yes, it will work, if you readjust the element lengths to account for the change
in velocity factor of the wires.  Losses may be slightly higher depending on the
dielectric properties of the insulation.

I'm building a 2m yagi using insulated wire wound on fiberglass rods and covered
with heat shrink tubing.  There are at least three different insulating materials
in immediate proximity to the wire, so I took the pragmatic approach to tuning
it:  I built the original modeled design using #8 aluminum wire, then replaced the
elements one at a time with the new type and adjusted each to get the same
pattern as the original antenna.  There was no significant difference in performance
or pattern between the two antennas when I was finished.
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K7KBN
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Posts: 2838




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« Reply #9 on: April 15, 2010, 09:33:21 AM »

"Will antenna work?"

Why ask?  Why not research it, build it, adjust it and see for yourself?  That way, you will gain experience and knowledge that only comes via actually doing the project work.

Things also depend on the exact definition of "work" as used in your question.

73 and have fun!
Pat K7KBN
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73
Pat K7KBN
CWO4 USNR Ret.
K2CBI
Member

Posts: 60




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« Reply #10 on: April 15, 2010, 02:29:43 PM »

For sure it will work.  Just look at the Hex Beam and Spiderbeam designs.  The insulation changes the velocity factor of the wire, but you can design for this.

Mike
K2CBI
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VE7RTB
Member

Posts: 5




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« Reply #11 on: April 16, 2010, 10:41:28 AM »

k7kbw<pat>
     ve7rtb
           have done it before.i have antenna build.the last one<1 to 1.3 swr>worked fine.i have the coax from another antenna <which worked fine>hooked up to the new antenna and this time used did not use bare wire.thank-you pat.back to the drawing board?HuhHuhHuh      
                           73's for now
                                 ve7rtb<rick>
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