HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jan 25, 2011, 02:43 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,060 Posts
Quote:
Originally Posted by Derek_S View Post
Right, on my 2.4 Vtx I fly CP on the GS and omni on the plane. However I still lose some signal in a bank, and I have wondered if the Patch sold to me from NG as CP is actually CP at all.
Typically they aren't. However remember that when you bank you are also exposing a null over the top of the antenna. You will also still have multipath interference.

-Alex
IBCrazy is offline Find More Posts by IBCrazy
RCG Plus Member
Sign up now
to remove ads between posts
Old Jan 25, 2011, 05:07 PM
Videopilot
Derek_S's Avatar
United States, NC, Charlotte
Joined May 2009
2,706 Posts
I am having trouble understanding how the stub/conductor match works. Does it replace the 1st 1/4 turn of the helix, bump it forward (so no helix length/section need be removed)?

And you mention height? This means that it begins at 'X' inches from the reflector? And the coax just feeds up to where it starts?
Derek_S is offline Find More Posts by Derek_S
RCG Plus Member
Latest blog entry: Iconic X
Reply With Quote
Old Jan 25, 2011, 08:18 PM
Fly FPV, sleep; repeat
twinturbostang's Avatar
Germantown, MD
Joined Mar 2006
3,373 Posts
Alex: Do you have a website with all of these antennas? Would be great to have a centrally located source for all your great stuff. I sometimes find myself having to dig through the pages here to find information on a particular antenna design.
twinturbostang is offline Find More Posts by twinturbostang
Reply With Quote
Old Jan 25, 2011, 10:53 PM
Who done it?
rawlmark's Avatar
Erie, CO
Joined Oct 2010
141 Posts
^^^ Just go to his blog. http://www.rcgroups.com/forums/member.php?u=103113. They're all there.
rawlmark is offline Find More Posts by rawlmark
Reply With Quote
Old Jan 25, 2011, 11:16 PM
Fly FPV, sleep; repeat
twinturbostang's Avatar
Germantown, MD
Joined Mar 2006
3,373 Posts
Excellent! Thanks!
twinturbostang is offline Find More Posts by twinturbostang
Reply With Quote
Old Jan 26, 2011, 02:35 AM
Registered User
SW England
Joined Aug 2009
799 Posts
Another job well done Alex.
Keep spreading the word and I'm sure circular polarisation will take on (off ?!!) even if most don't understand it and it's potential.

Currently, the Skew-Planar antenna (or PinWheel as OMM has dubbed it) is probably the simplest to build and gives an outstanding omni directional radiation pattern.

Nigel.
Devonboy is offline Find More Posts by Devonboy
Reply With Quote
Old Jan 26, 2011, 03:47 AM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,060 Posts
Quote:
Originally Posted by Derek_S View Post
I am having trouble understanding how the stub/conductor match works. Does it replace the 1st 1/4 turn of the helix, bump it forward (so no helix length/section need be removed)?

And you mention height? This means that it begins at 'X' inches from the reflector? And the coax just feeds up to where it starts?

Yes. You can feed it in from any direction. Build the helix as normal, then add the match.

Height is defined as the distance from the reflector to the bottom most part of the stub.

The coaxial cable feeds directly into the stub, yes.

-Alex
IBCrazy is offline Find More Posts by IBCrazy
RCG Plus Member
Last edited by IBCrazy; Feb 09, 2011 at 09:12 AM.
Reply With Quote
Old Jan 26, 2011, 03:49 AM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,060 Posts
Quote:
Originally Posted by Devonboy View Post
Another job well done Alex.
Keep spreading the word and I'm sure circular polarisation will take on (off ?!!) even if most don't understand it and it's potential.

Currently, the Skew-Planar antenna (or PinWheel as OMM has dubbed it) is probably the simplest to build and gives an outstanding omni directional radiation pattern.

Nigel.
Hopefully not for long. My Caltrop antenna should be a much easier to build solution. It won't be perfectly CP, but for most, it will do the job just fine

-Alex
IBCrazy is offline Find More Posts by IBCrazy
RCG Plus Member
Old Jan 26, 2011, 07:12 AM
Videopilot
Derek_S's Avatar
United States, NC, Charlotte
Joined May 2009
2,706 Posts
Quote:
Originally Posted by IBCrazy View Post
No, it doesn't replace the first 1/4 turn. You can feed it in from any direction. Build the helix as normal, then add the match.

Height is defined as the distance from the reflector to the bottom most part of the stub.

The coaxial cable feeds directly into the stub, yes.

-Alex
Ok, so helix distance from ground plane will be height of stub separation plus stub height (perpendicular from ground plane)? I think I got it.
Derek_S is offline Find More Posts by Derek_S
RCG Plus Member
Latest blog entry: Iconic X
Reply With Quote
Old Jan 26, 2011, 07:28 AM
Videopilot
Derek_S's Avatar
United States, NC, Charlotte
Joined May 2009
2,706 Posts
Quote:
Originally Posted by IBCrazy View Post
Ideally, the reflector should be round and not square. However I found this to be difficult, so I simply trimmed the corners from my square pattern. Really this makes little difference whether it’s round or square, but it keeps me from getting cut on the sharp edges anyway.

For my 1280MHz my reflector is 9-1/8” square
Out of curiosity, if a perfectly round one was made, would the diameter also be 9-1/8”? I may cut mine down closer to a circle, say octagonal?
Derek_S is offline Find More Posts by Derek_S
RCG Plus Member
Last edited by Derek_S; Jan 26, 2011 at 09:02 AM. Reason: speelin
Reply With Quote
Old Jan 26, 2011, 08:55 AM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,060 Posts
Derek,

To answer your questions:

The helix will actually start at the bottom of the round conductor matching stub. For the strip match, it doesn't matter. Like I said, wind the helical first, then add the stub. So long as the helix starts within 1/4" of the reflector, you'll be fine.

For the round reflector, yes. Diameter would be equal to one wavelength.

-Alex
IBCrazy is offline Find More Posts by IBCrazy
RCG Plus Member
Old Jan 26, 2011, 09:26 AM
Registered User
Zen09's Avatar
Germany, HB, Bremen
Joined Jun 2010
916 Posts
So the helical antenna with 10.5 dbi has a (vertical?) beamwith of 55 degrees, while
the biquad with 11 dbi gives about the same vertical beamwith ?!

But the helical gives 360 horizontal if I understand this, there wouldn't be many arguments for building the biquad, this antenna is awesome!
Zen09 is offline Find More Posts by Zen09
Reply With Quote
Old Jan 26, 2011, 09:30 AM
On a holiday?
boopidoo's Avatar
Uppsala, Sweden
Joined Sep 2008
3,467 Posts
Ouch, this antenna seems to be much harder to model in 3D. But I'll give it a go, it makes me better understand the build process.
boopidoo is offline Find More Posts by boopidoo
Reply With Quote
Old Jan 26, 2011, 09:31 AM
Videopilot
Derek_S's Avatar
United States, NC, Charlotte
Joined May 2009
2,706 Posts
Ok, I see, the impedance matchers run parallel alongside with the helix, similar to the Hecker transformer. Are they soldered all the way, or just at the origin/termination points?

I think I found pics that clearly illustrate it. Please correct me if they are different designs...


Derek_S is offline Find More Posts by Derek_S
RCG Plus Member
Last edited by Derek_S; Jan 26, 2011 at 09:43 AM.
Reply With Quote
Old Jan 26, 2011, 09:34 AM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,060 Posts
Just the origin and termination points, Derek. There is a shunt method, but that requires a VSWR meter which I'm sure nobody has. Those pictures show the match well.

-Alex
IBCrazy is offline Find More Posts by IBCrazy
RCG Plus Member
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Circular-polarized Patch Antenna for 5,8 GHz Lonestar78 FPV Talk 22 Oct 15, 2011 04:46 PM
Discussion Left/Right circular polarized antenna ? SpookiePower FPV Talk 44 Jun 04, 2011 06:41 PM
For Sale 2.4 gh 8 dbi patch antenna $10 norberto83 FPV Equipment (FS/W) 1 Dec 03, 2010 07:44 PM
Question 30 dBi Grid Antenna matyou FPV Talk 7 Nov 14, 2010 10:32 PM
Discussion Anyone tried building a helical antenna for FPV? Bill Sanford FPV Talk 20 Nov 04, 2010 06:48 PM