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icrashrc
Joined: 16 Mar 2006
Posts: 247
Location: Mishawaka, In
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 Posted: Mon Jul 14, 2008 9:36 pm Post subject: Dipole antenna from co-ax |
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I know I've seen on the list how to make a dipole antenna out of co-ax. I just spent the last hour searching the archives and can't find the post again. Anyone remember who had that info or know where to find it?
Thanks
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Scott
www.ill-EagleAviation.com
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George Alexander
Joined: 10 Jan 2006
Posts: 245
Location: SW Florida
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| Posted: Tue Jul 15, 2008 4:32 am Post subject: Re: Dipole antenna from co-ax |
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Scott:
From Boyd Young's Web Site:
http://www.brigham.net/~byoung/antenna.html
| icrashrc wrote: | I know I've seen on the list how to make a dipole antenna out of co-ax. I just spent the last hour searching the archives and can't find the post again. Anyone remember who had that info or know where to find it?
Thanks |
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George Alexander
FS II R503
E-LSA N709FS
http://www.oh2fly.net |
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mdnanwelch7(at)hotmail.co
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| Posted: Tue Jul 15, 2008 9:11 am Post subject: Dipole antenna from co-ax |
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Scott,
It has been awhile since I've looked at the design article, but Jim Weir (of Kitplane's Magazine) has a website that has the dipole antenna, with close-up drawings and details.
Just do a search for "Aero 'lectrics". I'll see if I can find it......
Here it is: (just scroll down to the article you're after. Best regards, Mike Welch
http://www.rst-engr.com/kitplanes/index.htm
P. S. Scott builds a beautiful overhead fiberglass panel. He custom made one for me...nice stuff.
_________________________________________________________________
It’s a talkathon – but it’s not just talk.
http://www.imtalkathon.com/?source=EML_WLH_Talkathon_JustTalk
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tlongo
Joined: 17 Jul 2007
Posts: 14
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| Posted: Tue Jul 15, 2008 10:41 am Post subject: Dipole antenna from co-ax |
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Hi Scott, this will work with any frequency you want to make a half wave
dipole for. Take the freq in mhz you want to make antenna for and divide it
into 468 and that is the correct length in feet. For instance 123.00 mhz
would be 468 divided by 123 equals 3.8 feet for your half wave. Now take 3.8
divided by 2 and you get 1.9 feet, so take 1.9 feet of wire and solder it to
center conductor of 50 ohm coax and 1.9 feet and solder to the shield of the
coax and you have a half wave dipole. If you want to make your own 1/4 wave
antenna take a 1.9 foot rod of aluminum or stainless and hook center of coax
to it and insulate that from ground when you mount it, then put shield of
coax to ground of airframe and you now have a 1/4 wave antenna that did not
cost an arm and a leg to buy. You can trim to a perfect SWR if you have a
meter but it will work fine if you just cut it to the proper length.
--
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icrashrc
Joined: 16 Mar 2006
Posts: 247
Location: Mishawaka, In
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| Posted: Sat Jul 19, 2008 11:58 am Post subject: Re: Dipole antenna from co-ax |
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Thanks to all!
George, Boyds site was the one i remembered.
Mike, Thanks for some interesting reading. And the kudos on the overhead panel. I'm glad you like it!
tlongo, I don't seem to have a program to open that file. And what type of co-ax is 50 ohm? rg-58, rg-59, rg-6, something else...?
Thanks again,
Scott
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ceengland(at)bellsouth.ne
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| Posted: Sat Jul 19, 2008 5:06 pm Post subject: Dipole antenna from co-ax |
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icrashrc wrote:
| Quote: |
Thanks to all!
George, Boyds site was the one i remembered.
Mike, Thanks for some interesting reading. And the kudos on the overhead panel. I'm glad you like it!
tlongo, I don't seem to have a program to open that file. And what type of co-ax is 50 ohm? rg-58, rg-59, rg-6, something else...?
Thanks again,
Scott
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-58 is 50 ohm. -59 & -6 are 75 ohm.
It should be noted that most, if not all rg-58 has a solid center
conductor. If it's installed where it doesn't move at all, it will
probably outlast you & the plane. However, if you're plugging &
unplugging from a hand-held & hang the dipole end so it can flex & move
as the plane moves, you might have problems with the center conductor
either breaking or pushing its way through the foam center insulation &
touching the shield. There are other 50 ohm coaxes that have a stranded
center conductor so they are more flexible.
Charlie
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tlongo
Joined: 17 Jul 2007
Posts: 14
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| Posted: Tue Jul 22, 2008 8:13 am Post subject: Dipole antenna from co-ax |
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Hi Scott, RG58 is 50 ohm RG59 & RG6 are 75 ohm, make sure you use RG59.
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by0ung(at)brigham.net
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| Posted: Tue Jul 22, 2008 7:44 pm Post subject: Dipole antenna from co-ax |
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Use 50 ohm coax..... the 75 ohm stuff is for cable tv. Or xmitter
designed for 75 ohm loads.
Your transmitter is designed for 50 ohm coax and matched to an antenna tuned
to a 1 to 1 match,, which is a 50 ohm impedance.
I am holding in my warm hands a piece of coax " PLASTOID CORP. RG- 58 A/U"
it is 0.2 inches in diameter, it has a braid just under the jacket, with an
insulator over the multi strand center conductor. BETTER STUFF.
If you want to go smaller..... I have some " BELDEN 8216 RG - 174 / U"
0.1 inch in diameter, also multi strand center core.... It has higher
internal losses but is good for low power and very short distances. GOOD
STUFF
There is one other but I cant remember the number off the top of my head.
Rg 222??????? It is usually brown in color and it is DOUBLE shielded and
is better suited for installations with lots of other RFI ( Radio Frequency
Interference) in the area. My best guess is 0.2 inches in diameter as
well. BEST STUFF. I considered it an over kill in my kolb.
Try to stay away from the coax with a solid core center wire unless it is
for an installation that will have no movement.
Boyd Young
Kolb MkIIIC
530 + hours
www.brigham.net/~byoung/antenna.html
there is not any tech info on the sight..... mostly a picture and short
description.
Ham Radio Extra Class N7WFM
| Quote: | >>>>>>>>>>>>>>>>>>
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Hi Scott, RG58 is 50 ohm RG59 & RG6 are 75 ohm, make sure you use RG59.
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rowedenny
Joined: 09 Mar 2008
Posts: 338
Location: Western PA
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| Posted: Wed Jul 23, 2008 6:57 am Post subject: Dipole antenna from co-ax |
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Boyd said,
[quote] Use 50 ohm coax..... the 75 ohm stuff is for cable tv. Or xmitter
designed for 75 ohm loads.
Your transmitter is designed for 50 ohm coax and matched to an antenna
tuned
to a 1 to 1 match,, which is a 50 ohm impedance.
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