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Old Mar 25, 2015, 05:04 PM
Wallop!
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Bussum, Netherlands
Joined Oct 2009
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I'm happy to do the maths for you Rodizio:

650MHz means a wavelength of almost half a meter.
A cloverleaf's diameter is a little bit less than two times a quarter wavelength.
So the diameter will be around 25 cm (10").

Martin
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Old Mar 25, 2015, 07:13 PM
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For the following: I am talking about a single lobe, not the big "S"...

Question 1)
According to the original spec, the angle that is 110 should be 114.593 in order to have a standard arc which can be calculated by

S = r * Theta

, where Theta is the angle between the two radii. Note that Theta is in RADIANS...

In my case (trying to make it for 5.845 GHz) which is very close to 5.8 GHz per spec:

S=26.263814 mm
r =13.131737 mm
Theta = 114.593 degrees

Should it not be a standard arc? (ie. bowing out a little due to 110 degree as opposed to calculated 114.593 degree)

Question 2)
I understand that we have to have some "loss" due to bending of the wires cause it is not a perfect bend... Should the arc length still be:

arc length = (length of the wire (ie: 53mm) - (2 * 1/4 wave length) ???

Thank you for your effort.

K
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Old Mar 25, 2015, 10:12 PM
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IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
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Quote:
Originally Posted by TheKaduu View Post
For the following: I am talking about a single lobe, not the big "S"...

Question 1)
According to the original spec, the angle that is 110 should be 114.593 in order to have a standard arc which can be calculated by

S = r * Theta

, where Theta is the angle between the two radii. Note that Theta is in RADIANS...

In my case (trying to make it for 5.845 GHz) which is very close to 5.8 GHz per spec:

S=26.263814 mm
r =13.131737 mm
Theta = 114.593 degrees

Should it not be a standard arc? (ie. bowing out a little due to 110 degree as opposed to calculated 114.593 degree)

Question 2)
I understand that we have to have some "loss" due to bending of the wires cause it is not a perfect bend... Should the arc length still be:

arc length = (length of the wire (ie: 53mm) - (2 * 1/4 wave length) ???

Thank you for your effort.

K
I believe you are over-thinking this, but yes you are correct.

-Alex
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Old Mar 26, 2015, 12:04 AM
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By the way, thank you Alex for putting this for everyone. It is such a service to the community...

"I believe you are over-thinking this"... So, the design is very forgiving then?

Thanks again!

K
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Old Mar 26, 2015, 10:33 AM
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It's hard to describe but with the Gaits FPV Mini Quad Racing I want to get everything quite in a smal space and a 2.4 vTx could fit a GoPro "inside".... is that a really bad idea or should I be fine for quad racing (so no long range at all)

Thanks!
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Old Mar 26, 2015, 12:57 PM
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Alex, can you confirm if the ultras connection 90 degree are touching the CF frame is bad? I had seen some speculate this.
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Old Mar 26, 2015, 01:39 PM
Wallop!
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Bussum, Netherlands
Joined Oct 2009
881 Posts
Quote:
Originally Posted by TheKaduu View Post
"I believe you are over-thinking this"... So, the design is very forgiving then?
"forgiving" is a relative measure. Compared to other antennas the cloverleaf sits somewhere in the middle when talking about bandwidth. But at 5.8GHz it's the small size that makes it hard to get the lengths correct. The angles between the lobes aren't critical. A few degrees less or more doesn't matter.

As for your second question, I don't think it matters much if the bend is not perfect as long as the wire length is correct. A wavelength remains a wavelength, also if there are sub-bends (that change the radiation pattern etc. a little bit).

Just my thoughts. No scientific proof
Martin
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Old Mar 26, 2015, 03:46 PM
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Originally Posted by IBCrazy View Post
I believe you are over-thinking this, but yes you are correct.

-Alex
Well, I already bought the Bluebeam Ultra set from GetFPV.com... I wanted to get it right and at least pay my due for using your specs for other models I may build the antennas for.

I have a question though... I have quadcopter. For that, I also bought 20cm extension to put the Airscrew on top of everything outside the cover for the HK H.A.L. frame I have. Would this extension setup affect the electronics and/or cause loss in the transmitted video signal?

Thank you for your time,

K
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Old Mar 26, 2015, 04:55 PM
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Quote:
Originally Posted by TheKaduu View Post
By the way, thank you Alex for putting this for everyone. It is such a service to the community...

"I believe you are over-thinking this"... So, the design is very forgiving then?

Thanks again!

K
Indeed it is very forgiving
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Old Mar 26, 2015, 04:56 PM
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Quote:
Originally Posted by ktmaprilia View Post
Alex, can you confirm if the ultras connection 90 degree are touching the CF frame is bad? I had seen some speculate this.
I have seen many people do this. I don't think it is a problem.

-Alex
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Old Mar 26, 2015, 04:57 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
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Quote:
Originally Posted by TheKaduu View Post
Well, I already bought the Bluebeam Ultra set from GetFPV.com... I wanted to get it right and at least pay my due for using your specs for other models I may build the antennas for.

I have a question though... I have quadcopter. For that, I also bought 20cm extension to put the Airscrew on top of everything outside the cover for the HK H.A.L. frame I have. Would this extension setup affect the electronics and/or cause loss in the transmitted video signal?

Thank you for your time,

K
Not to any discrenable level. I do this all the time for cleaner installations.

-Alex
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Old Mar 26, 2015, 05:08 PM
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Originally Posted by IBCrazy View Post
Not to any discrenable level. I do this all the time for cleaner installations.

-Alex
Fantastic! Thanks again.
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Old Mar 29, 2015, 05:52 PM
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Italy, Emilia-Romagna, Misano Adriatico
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Alex (or anyone else), is there any reason, RF wise, why I can't strip the outer plastic sheath and saturate the outer braid of my RG316 Clover cable to make it solid/semi rigid so that it doesn't flap about on my Bix3?

Tom.
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Old Mar 30, 2015, 01:46 AM
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Switzerland, LU, Buchrain
Joined Aug 2006
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Quote:
Originally Posted by Tommygunn View Post
Alex (or anyone else), is there any reason, RF wise, why I can't strip the outer plastic sheath and saturate the outer braid of my RG316 Clover cable to make it solid/semi rigid so that it doesn't flap about on my Bix3?

Tom.
Tom,

In theory the impedance of a coax is defined by the ratio of the inner diameter of the shield versus the outer diameter of the inner concuctor and the material used for insulation between the two, so - again in theory - your aproach would not change this. In fact semi rigid cable is exactly this, the braid is slightly tined to give it more stiffness. However, doing this all over the cable length by hand in a way such as you do not harm the insulation or change the diameter of the braid etc. seems very delicate/difficult.

Why not try a hassle free aproach and use some U-shaped tubing (i.e. use an outer insulation of a power cable or similar that you slit) that you put over the cable and then use some tape to close that U?

HTH

Markus
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