Nov 16, 2011, 09:11 AM
Registered FPVer :)
Switzerland, LU, Buchrain
Joined Aug 2006
2,924 Posts
Quote:
 Originally Posted by chatch15117 I'm doing a more accurate approach to my antenna build this time... plotting the drawings so I can have them exactly perfect. One odd thing - the arc length is 141.69 but my half wavelength is 147.605... why are these different? The angle I used is 110º
Based on what you say it's not clear to me wether you used Alex's measures as a base for the complete lobes or if you draw them according to what you think they should be and now realize that there is a difference.

Alex's measures do not only base on the wave lenght alone. There is the velocity factor of air that must be compensated, and depending on the antenna construction there are other correction factors that have to be applied. I.e. the more lobes one of those antennas is having, the shorter each lobe has to be because of one lobe affecting the function of the nearby lobes just to give you one example out of quite a few things to consider.

HTH

Markus
Nov 16, 2011, 11:03 AM
Engineer for Christ
Amherst, VA
Joined Jun 2006
11,030 Posts
Quote:
 Originally Posted by Vantasstic I'm flying my long range fixed wing FPV plane on 1280MHz and have a 5.8Ghz VTx/VRx system coming in for closer in 'video quadcoopter' use. I wanted to try CL antenna's on both platforms. Is there a 'preferred' OD MIG wire that will cover both freqs or just the range of diameters mentioned at the beginning of this thread?
.035" wire for the 1280MHz and .023" for the 5.8GHz for best results. Changing wire thickness changes the impedance.

-Alex
Nov 16, 2011, 11:49 AM
Suspended Account
United States, FL, Maitland
Joined Apr 2011
2,109 Posts
Quote:
 Originally Posted by markus123456 Based on what you say it's not clear to me wether you used Alex's measures as a base for the complete lobes or if you draw them according to what you think they should be and now realize that there is a difference. Alex's measures do not only base on the wave lenght alone. There is the velocity factor of air that must be compensated, and depending on the antenna construction there are other correction factors that have to be applied. I.e. the more lobes one of those antennas is having, the shorter each lobe has to be because of one lobe affecting the function of the nearby lobes just to give you one example out of quite a few things to consider. HTH Markus
No, I'm talking about simple geometry. The directions call for the lobe to be 1/2 wavelength long. So that's 614035/1040/4 per Alex's instructions. When you bend the curve, the arc length obviously does not change. The angle changes, and he says it is 110º. Unless you don't have a perfect arc you simply can't fit 1/2 wavelength in 110º with the two sides(the radius...) being 1/4 wavelength. The ending angle would be about 114.59º, not 110º

The angle is the ratio of the side to the raidus. This is simply 2.

Last edited by chatch15117; Nov 16, 2011 at 11:55 AM.
Nov 16, 2011, 11:59 AM
Registered User
United States, CA, Santa Clara
Joined Mar 2008
376 Posts
Quote:
 Originally Posted by chatch15117 No, I'm talking about simple geometry. The directions call for the lobe to be 1/2 wavelength long. So that's 614035/1040/4 per Alex's instructions. When you bend the curve, the arc length obviously does not change. The angle changes, and he says it is 110º. Unless you don't have a perfect arc you simply can't fit 1/2 wavelength in 110º with the two sides(the radius...) being 1/4 wavelength. The ending angle would be about 114.59º, not 110º

I also made a template for myself to create some 5.8Ghz clovers and got stuck at the same measurement. If I could get mine right I would post them here, I think they can make constructing the smaller clovers much easier just lay the cut wires on paper and bend to match etc.

-Charlie
 Nov 16, 2011, 12:15 PM Suspended Account United States, FL, Maitland Joined Apr 2011 2,109 Posts I'll wait for Alex to post back before I go bending more wires into non-optimal configurations . These things aren't cheap!
 Nov 16, 2011, 12:23 PM Flying low is expensive. United States, CO, Boulder Joined Jul 2008 2,398 Posts They're not Mig wire is... well... almost free
 Nov 16, 2011, 12:35 PM Registered User Florida Joined Mar 2007 1,046 Posts I'm not sure the center for the radius of the arc is the intersection of the 2 base legs. If you make the radius a little shorter, and move the center for the arc a bit further up, you can fit a longer length of arc between the same 2 points. (this will also make the angle at those points a bit larger than 90 degrees)
Nov 16, 2011, 12:41 PM
Suspended Account
United States, FL, Maitland
Joined Apr 2011
2,109 Posts
Quote:
 Originally Posted by pdiddyg40 They're not Mig wire is... well... almost free
Time is money . I spent like 3 hours on the last set that didn't work

Quote:
 Originally Posted by yzguy I'm not sure the center for the radius of the arc is the intersection of the 2 base legs. If you make the radius a little shorter, and move the center for the arc a bit further up, you can fit a longer length of arc between the same 2 points. (this will also make the angle at those points a bit larger than 90 degrees)
That may be it. But I was drawing from this picture in OP.

Last edited by chatch15117; Nov 16, 2011 at 12:57 PM.
 Nov 16, 2011, 01:16 PM Nakelp United States, NJ, Union Joined Sep 2004 6,805 Posts Hey guys, I need some help. :-) I am trying to find ready made 5.8 Ghz antennas (Alex's Blue Beam) and it seams no one have them in stock even the Master :-). I am not able to make my own since i do not have a tools to calibrate or access to exact wire. So would someone here be able to make a set for me. Oh, I am not asking for freebee. Thx.
Nov 16, 2011, 02:45 PM
Registered FPVer :)
Switzerland, LU, Buchrain
Joined Aug 2006
2,924 Posts
Quote:
 Originally Posted by nakelp86 Hey guys, I need some help. :-) I am trying to find ready made 5.8 Ghz antennas (Alex's Blue Beam) and it seams no one have them in stock even the Master :-). I am not able to make my own since i do not have a tools to calibrate or access to exact wire. So would someone here be able to make a set for me. Oh, I am not asking for freebee. Thx.
I build a pair fine tuned SPW/CL for you if you want. I ask \$20 per antenna. Registered shipping is \$15.50 if you are within the EU, \$18 elsewhere. Send me a PM if you are interested.

Markus
Nov 16, 2011, 02:59 PM
Registered FPVer :)
Switzerland, LU, Buchrain
Joined Aug 2006
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Quote:
 Originally Posted by chatch15117 No, I'm talking about simple geometry. The directions call for the lobe to be 1/2 wavelength long. So that's 614035/1040/4 per Alex's instructions. When you bend the curve, the arc length obviously does not change. The angle changes, and he says it is 110º. Unless you don't have a perfect arc you simply can't fit 1/2 wavelength in 110º with the two sides(the radius...) being 1/4 wavelength. The ending angle would be about 114.59º, not 110º The angle is the ratio of the side to the raidus. This is simply 2.
I think I understood you well. What I tried to say is that Alex numbers of the legs and angles etc. are only aproximations as you don't need that angle if you follow his build instructions. You only need it if you want to do what you do. So, if you want to end up with the same thing like in the instructions, draw them the same way. In other words, draw the legs with the measures given, then make an arc between the two that is the given wire lenght minus the two legs.

I already build quite a few of those antennas and I don't know which frequency you are targeting. If it's 5.8, no chance to get it optimal no matter what build quality you use. There are too many factors. So your work will be an aproximation, but at the same time I can tell you that it will work, and it will work better than linear antennas. It will be a matter of luck how well it will work, and no single antenna will be the same. That's totally ok if you don't strive to make a range record and are happy with an average result which again is probably fine for many people.

If the frequency is 2.4, or lower, things are a lot more relaxed and the antenna will be close to your targeted frequency. Again, if you intend to end up with a resonant antenna on a given 5.8Ghz band frequency, you won't have a chance without the propper measuring equipement. I have optimized my build process to a very very high degree and still I have to tune every single antenna on my vector network analyzer. When measuring out antennas made by others or those first ones I made myself, I could see how much off I was. Usually pretty dramatic, like 100 or even 200Mhz or more. However, the antennas worked. Only range and picture quality are not on par with really fine tuned ones.

Markus
 Nov 16, 2011, 03:46 PM Suspended Account United States, FL, Maitland Joined Apr 2011 2,109 Posts I'm buiding for 1040MHz. Thanks.
Nov 16, 2011, 04:08 PM
Registered FPVer :)
Switzerland, LU, Buchrain
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Quote:
 Originally Posted by chatch15117 I'm buiding for 1040MHz. Thanks.
That should be fairly relaxed. So don't overthink this. If the overall lenght of your drawing matches the wire measures given by Alex in their total lenght you are definately ok. The angle and as a result even the shape of the arc are not so very critical - especially not on lower freuqencies.

Markus
Nov 16, 2011, 04:15 PM
Registered User
Joined Apr 2011
1,790 Posts
Quote:
 Originally Posted by markus123456 I build a pair fine tuned SPW/CL for you if you want. I ask \$20 per antenna. Registered shipping is \$15.50 if you are within the EU, \$18 elsewhere. Send me a PM if you are interested. Markus
I'll take you up on your offer (PM you later)....but a quick question...how does the tuning affect the individual frequency...for example with this 5.8 Rx,

( CH1:5705 - CH2:5685 - CH3:5665 - CH4:5645 CH5:5885 - CH6:5905 - CH7:5925 - CH8:5945)

are you tuning for one particular channel?? And if so how much is the effect if you have to switch to another channel.

I'm just curious as to how it all works / relates.....thx
 Nov 16, 2011, 04:45 PM Nakelp United States, NJ, Union Joined Sep 2004 6,805 Posts Markus PM sent :-) Thx.