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Old May 15, 2011, 08:01 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
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Quote:
Originally Posted by mark hitchman View Post
I was wondering what happens if you use a reflector which is way too big?
I am using a 6 turn 1010mhz helical with my computer case door as the reflector. It has worked really well and I was about to get a piece of galv sheet cut the correct size but did not want to lose any performance. Would the correct size work better for long distance or the oversize one?




Mark
In general that will only increase the size of the sidelobes slightly. It will reduce gain very little as the signal is pushed to the sides just a bit.

-Alex
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Old May 15, 2011, 10:41 PM
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mark hitchman's Avatar
New Zealand
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Quote:
Originally Posted by IBCrazy View Post
In general that will only increase the size of the sidelobes slightly. It will reduce gain very little as the signal is pushed to the sides just a bit.

-Alex
Thanks Alex, I will cut out a circular one the right size then and test it out. My official test is at what altitude I lose video at 10km, a touch and go would be nice

Mark
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Old May 17, 2011, 01:24 AM
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Hello,
can I use a pcb as a reflector? How would it influence the performance?
Thanks
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Old May 17, 2011, 03:12 AM
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Singapore
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I've finally did some test.

I'm running on a 1200Mhz using the Fox700 tx

My previous setup was a stock rubber antenna for my Rx and a V-antenna for my Tx. The video got blurred during sharp banks and turned into black and white sometimes fading with flashes in an random pattern when i exceed flying beyond 1200ft LOS.

Now with the new helical antenna + Clover combo, i got clear images all the way, even beyond 1200ft. There are still flashes but it happens in one short burst (100ms) for every min which is many more times better than my previous combo.

Thanks IBCrazy for your wonderful tutorials and guides to making superb antennas.
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Old May 18, 2011, 05:00 PM
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Quote:
Originally Posted by aSa2 View Post
Hello,
can I use a pcb as a reflector? How would it influence the performance?
Thanks
IBCrazy, could you please give me the answer
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Old May 18, 2011, 09:17 PM
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It will work fine. No problems.
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Old May 18, 2011, 09:30 PM
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IBcrazy, Would 17 gauge copper wire work? If not, I will just make a SPW and make the helical later.
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Old May 19, 2011, 02:34 AM
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Joined Oct 2009
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Coil spacing

Thanks for these tutorials, I built two antennas SPW and CL, with surprising results!
Now I like to build the helical for my 5.8 ghz kit
I read the tutorial but I found a discrepancy in the coil spacing measure

in detail:

Cross insulated Helix for 5800Mhz:
Cross width in inches: 3600/f in MHz (+/- 10% tolerance) 15.7mm
Coil spacing in inches = 2900/f in MHz 12.7mm
Cross length = number of turns * coils spacing 3x1.27=38.1mm
Reflector plate size = 11732/f in MHz 51.4mm

later in the tutorial I read this:

For my wooden former, I marked the following on one side:
0, 2.1875, 4.375, 6.5625, 8.75, 10.9375
1280x2.1875= 2800 !!!


Coil spacing in inches = 2900/f in MHz or 2800/f in MHz ?

maybe I'm doing something wrong...
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Old May 19, 2011, 03:06 AM
Kiwi in Germany
whakahere's Avatar
Germany
Joined Jun 2010
2,259 Posts
Quote:
Originally Posted by -katana- View Post
Thanks for these tutorials, I built two antennas SPW and CL, with surprising results!
Now I like to build the helical for my 5.8 ghz kit
I read the tutorial but I found a discrepancy in the coil spacing measure

in detail:

Cross insulated Helix for 5800Mhz:
Cross width in inches: 3600/f in MHz (+/- 10% tolerance) 15.7mm
Coil spacing in inches = 2900/f in MHz 12.7mm
Cross length = number of turns * coils spacing 3x1.27=38.1mm
Reflector plate size = 11732/f in MHz 51.4mm

later in the tutorial I read this:

For my wooden former, I marked the following on one side:
0, 2.1875, 4.375, 6.5625, 8.75, 10.9375
1280x2.1875= 2800 !!!


Coil spacing in inches = 2900/f in MHz or 2800/f in MHz ?

maybe I'm doing something wrong...
I based mine off the mid ground frequency. So 5705mhz therefore my measurements came out pretty easy

I brought a 16 mm wooden dowel
13mm spacing
and my reflector was something like 5.something square.

It is not hard to make at all. The hardest part is making the hecker transformer. I believe mine is off somehow but I have nothing to test it on.
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Old May 19, 2011, 08:12 AM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,408 Posts
Quote:
Originally Posted by -katana- View Post
Thanks for these tutorials, I built two antennas SPW and CL, with surprising results!
Now I like to build the helical for my 5.8 ghz kit
I read the tutorial but I found a discrepancy in the coil spacing measure

in detail:

Cross insulated Helix for 5800Mhz:
Cross width in inches: 3600/f in MHz (+/- 10% tolerance) 15.7mm
Coil spacing in inches = 2900/f in MHz 12.7mm
Cross length = number of turns * coils spacing 3x1.27=38.1mm
Reflector plate size = 11732/f in MHz 51.4mm

later in the tutorial I read this:

For my wooden former, I marked the following on one side:
0, 2.1875, 4.375, 6.5625, 8.75, 10.9375
1280x2.1875= 2800 !!!


Coil spacing in inches = 2900/f in MHz or 2800/f in MHz ?

maybe I'm doing something wrong...
Actually, either works fine. This antenna is VERY wideband (as in +/- 80MHz). The precise measurement is 2850. So either 2800 or 2900 works.

-Alex
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Old May 20, 2011, 08:38 AM
SPG
Sydney, Australia
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Joined Jan 2010
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My first atempt at making a 2.4G Helical.

Freq = 2510Mhz
Number of turns = 6 (10.5 dbi)
PVC pipe former outer diameter = 42mm
Coil spacing = 28mm
Reflector plate size =118mm
The IBCrazy microstrip Width = 5.7
The IBCrazy microstrip height = 4.6

Wire, 1.25mm enameled copper.
Reflector, Blank Printed circuit board.

Wasn't too hard to make and hopefully I haven't messed up any of the calculations. It's quite light so won't be a problem for the tracker. I'll be testing it on Sunday.
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Old May 20, 2011, 09:57 AM
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United States, CA, Rancho Palos Verdes
Joined Sep 2010
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Hey I was going to put mine on a tracker, too, but was worried about the weight (of course, I'm using a 900 mhz version). Let me know if you've bench tested or actually flown with the helical/tracker and how it works. Thanks.
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Old May 20, 2011, 10:01 AM
SPG
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Quote:
Originally Posted by Infernal Bill View Post
Hey I was going to put mine on a tracker, too, but was worried about the weight (of course, I'm using a 900 mhz version). Let me know if you've bench tested or actually flown with the helical/tracker and how it works. Thanks.
The 2.4G version will be alot smaller than the 900M. I also use blank PCB for the reflector which is a bit lighter than sheet metal. So not probs using a tracker. Haven't tested it's RF performance yet though.
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Old May 20, 2011, 10:05 AM
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United States, CA, Rancho Palos Verdes
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Yup, but it looks like you've got more turns than me. Mine is shorter and fatter. We're still talking about antennas, though, right?

Thanks for the heads up.
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Old May 20, 2011, 10:49 PM
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Amherst, VA
Joined Jun 2006
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Bill, ReadymadeRC has CP patches that will fit an antenna tracker: http://www.readymaderc.com/store/ind...roducts_id=489

Axial ratio isn't nearly as good as your helical (.75 vs.95), but it does just fine for me.

And before anyone asks, no it is not the same as the goof-proof patch.

-Alex
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