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Old May 17, 2012, 01:38 PM
At peace with his albatross
wannabe's Avatar
United States, CA, Vacaville
Joined Oct 2003
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Quote:
Originally Posted by IBCrazy View Post
Too bad you don't live near me or I'd tune it in for you. I'd like to see that with my own eyes. It really is a nice piece of work.

_Alex
Thanks for the offer and compliment, Alex!

I am thinking of asking a local Ham club member to hook it up to an SWR meter. But I'm not sure what data they will need to test it. For example will they need to know exactly what RF I am tuning for, or will 5800mhz be sufficiant?

Other things to consider for tuning?

Also I may not have the right connector adapter to go from SMA to their gear.

Your thoughts on that Alex?
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Old May 19, 2012, 11:56 PM
At peace with his albatross
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United States, CA, Vacaville
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A much cleaner second attempt. I still have no idea if its tuned properly but I am more comfortable with the measurements and the solder joints.

5.8GHz
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Old May 20, 2012, 12:54 PM
I think I'm inverted. Maybe.
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United States, CA, Pacifica
Joined Apr 2012
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Which would be my best bet if I bolt this to a tracker? This or your patch antenna?
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Old May 20, 2012, 01:35 PM
home of the best antennas
United States, FL, Boca Raton
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well, even with good measurements, your swr at 5.8 will be hit or miss, you don't know at what channel your best swr is, and if it's 1.1:1 at 5705, for example at 5905 it will be much worse, in the 2.5:1 range from experience...

It just really needs to be measured.

They will still outperform the stock antennas even if you don't swr tune them though...

check this set out.

It took me 3 tries to get a good swr for the SPW in the picture, as it can't really be tuned too much, The first one I made was 5945, the second 5885, the third 5740, first the swr was at 1.4:1 than I added a large drop of hotglue and it fell to 1.2:1 That's how finiky they are..

One drop of glue and it messes up your work, or fixes it.
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Old May 21, 2012, 03:55 PM
Engineer for Christ
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Amherst, VA
Joined Jun 2006
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Quote:
Originally Posted by acetech09 View Post
Which would be my best bet if I bolt this to a tracker? This or your patch antenna?
Probably a helical. CP beats LP hands-down for FPV.

-Alex
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Old May 21, 2012, 03:55 PM
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Amherst, VA
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Originally Posted by wannabe View Post
A much cleaner second attempt. I still have no idea if its tuned properly but I am more comfortable with the measurements and the solder joints.

5.8GHz
Your first turn looks a little flat. Move the first 1/4 turn upward slightly. This will help your SWR.

-Alex
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Old May 21, 2012, 04:18 PM
The squidman
United States, FL, Jacksonville
Joined Dec 2011
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Where is best place to buy copper tubing or 10-14 AWG wire? And for heck transformer can i use same galvanized material as i use in my reflector?

-Thank, Sky
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Old May 21, 2012, 04:36 PM
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Amherst, VA
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I used galvanized steel for the Hecker transformer. If you have no measuring equipment, the Hecker is usually your best bet.

I buy my wire from the hardware store in a bulk roll. Probably more economical to buy a couple feet of romex and strip out the wire you need, though.

-Alex
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Old May 21, 2012, 08:42 PM
Assault the sky
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United States, CO, Denver
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Acetech, also look at the crosshair. CP but the size of a patch.
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Old May 21, 2012, 09:38 PM
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United States, IA, Orange City
Joined Feb 2012
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Testing helical antenna

Tonight my wife and I tested out my first attempt at a helical antenna. I compared the helical with my cloverleaf antenna (which is proven out to 2km on my plane) by driving our Saturn line of sight and marking where the signal dropped off.

Unfortunately both antennas dropped out at around 1.2km, but that exact spot was under an intersection of two power lines.

I'm excited to see what this helical can do with my plane in the air. Can you see any areas of improvement on this helical?
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Old May 22, 2012, 06:59 AM
New RC geek!
Joined Apr 2012
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Hi
I have a few quick questions.
Can I use a copper cable that is hollow?
If I make a round reflector plate, what should the diameters be? I am using 2.4GHz(2450mhz)
Thanks
Inge
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Old May 22, 2012, 07:09 AM
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Switzerland, LU, Buchrain
Joined Aug 2006
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Quote:
Originally Posted by ricknoon View Post
Tonight my wife and I tested out my first attempt at a helical antenna. I compared the helical with my cloverleaf antenna (which is proven out to 2km on my plane) by driving our Saturn line of sight and marking where the signal dropped off.

Unfortunately both antennas dropped out at around 1.2km, but that exact spot was under an intersection of two power lines.

I'm excited to see what this helical can do with my plane in the air. Can you see any areas of improvement on this helical?
First off, I asume it's for 5.8Ghz.

- The feedpoint is the weakest spot imho. Make the hole directly below the end of the helix, then solder in the mesh of the coax to the reflector by just leaving the mes as is. In other words, deisolate the outer isolation to the reflector thickness plus say half a milimeter. That way the feedpoint is as tight as it gets. The feedpoint as you have it now will radiate on it's own due to it's kind, lenght and size.
- The angle of the helix seems to be on the flat side.
- The wire used seems a bit thick. That will lead to a very wideband antenna. Probably ok since you most likely won't be able to tune it anyways.
- I don't see any kind of impedance transformer. Meaning no wavetrap, no hecker transformer.

HTH

Markus
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Old May 23, 2012, 09:23 AM
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Quote:
Originally Posted by markus123456 View Post

- I don't see any kind of impedance transformer. Meaning no wavetrap, no hecker transformer.
I have heard that having the first 1/4 turn parallel to the reflector is one way to do impedance matching, but I don't know too much about that method
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Old May 23, 2012, 01:12 PM
At peace with his albatross
wannabe's Avatar
United States, CA, Vacaville
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Quote:
Originally Posted by IBCrazy View Post
Your first turn looks a little flat. Move the first 1/4 turn upward slightly. This will help your SWR.

-Alex
Dosent the wave trap have to be paralell with the reflector?
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Old May 23, 2012, 01:23 PM
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United States, TX
Joined Oct 2010
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Making one on Sat. Did a quick model in SW and just finished up my cam operations with solidcam. Desgined using Alex's equations. 2450Mhz, 6 turn. the coil supports will be machined from 1/8" clear acrylic sheet, the end and base caps will be 1/4" blue acrylic. Acrylic parts will be solvent welded. Coil will be wound from 1/8" diameter copper bus wire. Reflector plate will be machined from 1/8" 6061 sheet. Should take a couple of hours. Ill post a real pic when its done. Cool thing about CNC using sw/solidcam is what you see in the model is exactly what you produce

Solidworks Rendering of a 2450Mhz Helical (0 min 20 sec)
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