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Old Jan 25, 2013, 04:55 AM
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Switzerland, LU, Buchrain
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Originally Posted by Cheese5 View Post
How does this helical look? Shooting for 5.945ghz hopefully this with the wide bandwidth falls somewhere near it.

Is there a way to keep the copper from rusting? Acrylic paint?
Note, the centre wire from the point where the mesh connects to the helical coil technicalls spoken is now also part of the coil in your design!

You better would have feed the coil from the back by drilling a hole into the reflector at the spot wher it should meet the end of the coil. Then solder the mesh to the reflector and the center wire with only about 0.5mm spacing directly to the coil. You of course also can side feed it (albeit the coax will have some small negative impact) but then you would have to run the ground mesh as close to the coil as you manage!

It probably still will work, but the way you feed the helical will have significant impact on the impedance matching of the antenna. Since this is what you most likely can't measure, you have a little problem here. Note though that it could be "good" or bad - we just don't know. It's more likely to be bad though as that little part of center wire will radiate too.

HTH

Markus
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Old Jan 25, 2013, 05:31 AM
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Melbourne, Australia
Joined Apr 2009
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Originally Posted by nrg2go View Post
So my very first Helix

Hopefully she works well.

Attachment 5061424Attachment 5061425Attachment 5061426Attachment 5061429

Edit: I think I mis-interpreted the wave trap positioning? I put the middle of the trap at the 1/4 turn, when the trap should be in the middle of the 1/4 turn. Do you think it will put it way out?
I bottom fed mine, pics back at post 1024, need to make another one as I gave this one to a mate of mine.
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Old Jan 25, 2013, 08:04 AM
I can fly this plane
Kingdom of Sweden, Gävleborg County, Sandviken
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Will painting the reflector have any negative effect on performance?
I was thinking of protecting the copper from corrosion.
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Old Jan 25, 2013, 08:16 AM
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Originally Posted by PinDuke View Post
Will painting the reflector have any negative effect on performance?
I was thinking of protecting the copper from corrosion.
Painting the helical usually lowers the resonant frequency a bit. Do not use any paint that contains carbon or any other conductive material. Painting the reflector allone should not hurt.

HTH

Markus
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Old Feb 02, 2013, 08:00 PM
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Thanks Marcus, got it working well.
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Old Feb 03, 2013, 06:01 AM
9W2DLR
Malaysia, Federal Territory of Putrajaya, Putrajaya
Joined Nov 2011
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thw formula for pvc former said 3000 - 4600/in Mhz which mean smallest pvc outer diameter i can use is 2.343" for 1280Mhz correct?
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Old Feb 03, 2013, 10:24 PM
9W2DLR
Malaysia, Federal Territory of Putrajaya, Putrajaya
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this my 1280Mhz 5 turn helix, not my best but hopefully it work, i used a very thick galvanized steel wire instead of copper, i use rg316 as i do t have rg58 hopefully it do the job for now

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wave trap

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painted and waiting it to dry right now

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Old Feb 04, 2013, 04:36 AM
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Originally Posted by skellator View Post
thw formula for pvc former said 3000 - 4600/in Mhz which mean smallest pvc outer diameter i can use is 2.343" for 1280Mhz correct?
I don't know to what formula you refer, but I usually recommend people to use THIS online calculator to get the propper numbers:

http://jcoppens.com/ant/helix/calc.en.php

It bases on formulas given by the ARRL handbooks (forgot which one exactly) which are profen to be correct.

HTH

Markus
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Old Feb 04, 2013, 04:40 AM
9W2DLR
Malaysia, Federal Territory of Putrajaya, Putrajaya
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Originally Posted by markus123456 View Post
I don't know to what formula you refer, but I usually recommend people to use THIS online calculator to get the propper numbers:

http://jcoppens.com/ant/helix/calc.en.php

It bases on formulas given by the ARRL handbooks (forgot which one exactly) which are profen to be correct.

HTH

Markus
formula from the first page of course , to late for that now
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Old Feb 04, 2013, 08:10 AM
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Amherst, VA
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^You are fine. My calculations are based on the ARRL antenna bok Chapter 19 - Antennas for space communications.

-Alex
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Old Feb 04, 2013, 08:22 AM
9W2DLR
Malaysia, Federal Territory of Putrajaya, Putrajaya
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Originally Posted by IBCrazy View Post
^You are fine. My calculations are based on the ARRL antenna bok Chapter 19 - Antennas for space communications.

-Alex
great but this thing is hugeeeee i need a new tripod i dont think my small current tripod can survive

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Old Feb 06, 2013, 10:41 PM
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United States, CA, Ukiah
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5.8 ghz helical

This is my first 5.8 ghz helical, I used a 11/16" outside diameter plastic tube with 6 turns of copper wire. I get a good signal over a 90 degree arc at 3/4 mile away with a 500mw cloverleaf tx. I can't wait to finish a couple more of these and put them on IB's antenna tracker, I think I could get at least a couple of miles of range with this setup.
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Old Feb 07, 2013, 03:41 AM
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Originally Posted by devinvagt View Post
This is my first 5.8 ghz helical, I used a 11/16" outside diameter plastic tube with 6 turns of copper wire. I get a good signal over a 90 degree arc at 3/4 mile away with a 500mw cloverleaf tx. I can't wait to finish a couple more of these and put them on IB's antenna tracker, I think I could get at least a couple of miles of range with this setup.
Is the antenna coil wire on top really bent inwards and penetrates through the tube to the inner side? If so, bad idea.

The other thing is that the feed gap is on the very longish side of things. You better use a copper sheet for the reflector and bring the coax in from the back through a hole directly at the spot where the coil ends. You then can solder the mesh directly to the reflector and have a tight connection of the center pin to the start of the coil.

For "several miles" you should eventually increase the number of turns to 8.

HTH

Markus
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Old Feb 07, 2013, 12:01 PM
Hitech soaring
Germany, BW, Stuttgart
Joined Jan 2013
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IBCrazy Cross Helix please check

Hello IBCrazy, this is my 1280Mhz Helix made with your calculations for the cross Helix. Do you think I am still right in size with this material? We used 3mm Makralon (Plexiglas) and PCB material for the reflector.
I used a Helix diameter of 70,8mm and a 1turn distance of 55,56mm as you calculated for the cardboard version. Do I have to modify the size?

Regards Peter
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Old Feb 07, 2013, 01:16 PM
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Amherst, VA
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@Pitpilot - We have a term for that antenna: Perfection. Nice work! Now you just need to hook up your cable to it.
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