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Old Apr 15, 2015, 02:14 PM
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Originally Posted by IBCrazy View Post
I have never seen a setup like that in my life. I'm not sure how it works without a coupling mechanism unless something is buried in that box that I don't know about. All of mine get tuned on a Daiwa SII or a Field Fox vector network analyzer.

That said, something is not right. I don't know what it would be, though. It could be cable resonance, but your cables are not exceptionally long. Can you place your hand on the cables and see a change in your graph?

Other than that, you can send the antenna back to me for testing. I have a $12,000 that will tell the tale immediately without question.

-Alex
Hi Alex,
That little box is a mini-circuits directional coupler...
Antenna at the IN port, spectrum analyzer in the CPL port and a signal generator connected to the out port.
All cables are semi rigid ones, and I did not experience any changes...

Anyway, I arranged a session with a friend of mine, who has access to a lab full of outrageously expensive equipments...

Let's see.
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Old Apr 15, 2015, 09:58 PM
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Originally Posted by eosbandi View Post
Hi Alex,
That little box is a mini-circuits directional coupler...
Antenna at the IN port, spectrum analyzer in the CPL port and a signal generator connected to the out port.
All cables are semi rigid ones, and I did not experience any changes...

Anyway, I arranged a session with a friend of mine, who has access to a lab full of outrageously expensive equipments...

Let's see.
Perfect! That will certainly tell the tale. I always wondered how well these RFExplorers worked for VNA's. I guess we will find out.

-Alex
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Old Apr 16, 2015, 09:47 AM
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The only way out known to me is to measure out every single antenna, then take corrective measurements, measure again and so on up until you reach a satisfying result. This process - when taken seriousely - can take anywhere from 30 mins to more than one hour per antenna...
Markus,

Thanks for your reply. Can you elaborate on tuning post build? The construction methods outlined would suggest starting with new elements. as after cut and bent I see no feasible way to change the lengths.
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Old Apr 16, 2015, 10:33 AM
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I NAILED ONE! wooooohooo!

1.35 on all channels.

My VSWR meter is not super precise but it has been shown to be extremely consistent. Its a arduino controlled setup that cycles through the 8 Vtx channels retains the vf for each then test vr and calculates the VSWR and outputs to LCD.

As such the analog input is only so precise but adequate for building.

What I learned today: the solder application is critical to the result.

Thank you Markus for pointing this out.
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Old Apr 16, 2015, 10:51 AM
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Originally Posted by Tuxit09 View Post
I NAILED ONE! wooooohooo!

1.35 on all channels.

My VSWR meter is not super precise but it has been shown to be extremely consistent. Its a arduino controlled setup that cycles through the 8 Vtx channels retains the vf for each then test vr and calculates the VSWR and outputs to LCD.

As such the analog input is only so precise but adequate for building.

What I learned today: the solder application is critical to the result.

Thank you Markus for pointing this out.
I usually tune mines by heating up the solder joints and moveing the elements a bit up or down. Big corrections are made in the center, smaller ones on the outer conneciton (GND side). However, I do build my antennas slightly different in that every lobe is always a "bow" on it's own.

Then, bending the lobes slightly up or down makes a difference too, but only if the beding is very small as otherwise you change the behaviour of the antenna, most importantly it's radiation pattern which is something you don't want.

HTH

Markus
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Old Apr 16, 2015, 11:13 AM
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Originally Posted by markus123456 View Post
I usually tune mines by heating up the solder joints and moveing the elements a bit up or down. Big corrections are made in the center, smaller ones on the outer conneciton (GND side). However, I do build my antennas slightly different in that every lobe is always a "bow" on it's own.

Then, bending the lobes slightly up or down makes a difference too, but only if the beding is very small as otherwise you change the behaviour of the antenna, most importantly it's radiation pattern which is something you don't want.

HTH

Markus
Hey Markus, when you say that each lobe is its own bow, I thought that's how most people are doing it? Can you elaborate a bit on how your method differs from say the rcexplorer method?
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Old Apr 16, 2015, 11:21 AM
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akcom,

I think he means instead of doing it as the OP outlines with one long wire length and one short length to achieve 3 lobes just building with 3 short lengths as to make individual lobes

I have tried it both ways and I agree with Markus that individual lobes are much easier to make and yield more consistent results.

Markus, Thanks again for all your input please correct my above interpretation if in error.
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Old Apr 20, 2015, 04:07 PM
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How wide is a 900mhz cloverl eaf antenna? Has anyone found an easy solution to cover these?

I want to protect one from rollovers in a car, or when my plane find a tree.
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Old Apr 25, 2015, 10:02 AM
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Hi Alex

Do I have to mount this antenna up on the top of My craft (lobes facing up) or can I mount it on the bottom or side or rear? I'm trying to get some separation on a 450 Tri.
I would like to mount it on the bottom lobes facing down.

Dave
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Old Apr 25, 2015, 10:17 AM
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Originally Posted by Ruken View Post
How wide is a 900mhz cloverl eaf antenna? Has anyone found an easy solution to cover these?

I want to protect one from rollovers in a car, or when my plane find a tree.
Just guessing but i would think about 5- 6 inches.
That thing will be big you will need to build one of those hexagonal radar domes over it. That will look cool on the back of your car and will completely stop the car from rolling over but will tip it over a lot
You might want to try a different design maybe a Turnstile would be better suited for the trucking end of things and is CP as well
a vertical dipole as well could work well
We will see what Alex thinks he's the genius behind this stuff
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Old Apr 26, 2015, 06:00 AM
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Quote:
Originally Posted by fliteline dave View Post
Do I have to mount this antenna up on the top of My craft (lobes facing up) or can I mount it on the bottom or side or rear? I'm trying to get some separation on a 450 Tri.
I would like to mount it on the bottom lobes facing down.

Dave
The antenna has to be vertical. It does not matter if you let it hang down or stand up. NOT to the sides as the antenna has a null along the axis where you most likely have the cable.

HTH

Markus
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Old May 03, 2015, 11:25 AM
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How well does this pair with the Airblade? If I would have the Airblade on the rx and a Cloverleaf on the tx?

I have bought the Airblade set but I'd also like to build my own antenna. Cloverleaf would be easier to build after I crash and ruin my tx Blade.
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Old May 03, 2015, 01:17 PM
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Left handed vs Right handed polarization

I may be confused about how to tell Right Hand polarization from Left hand polarization, especially with respect to Clover Leaf, but also with respect to helical antennas, which I think are always(?) circularly polarized too, right?

I have attached a photo I took of two clover leaf antennas I purchased. These antennas were purchased from the same source together. I believe they are the same polarization. Perhaps I need help with this, but here is the method I have been told to use. If, when viewed from the top the pointed edge of the leaves point in a direction that would "cut" if rotated clockwise, then that is considered LEFT handed polarization. If, on the other hand the pointed parts of the leaf point in a direction that would "cut" if the antenna is turned in a counterclockwise direction, then that is RIGHT handed polarization. Is that right?

What is the rule for determining polarization of helical antennas?

One has 3 leaves and the other 4. Is the reason we put the 3 leaf antennas on transmitters just to decrease weight or is there another reason?

Thanks. Please be sure of your answer. I would appreciate a reference. Mine came from a Flite Test video, but as I said I may not have gotten it right.
Flite Test - Cloverleaf Antenna - FLITE TIP (8 min 53 sec)

VJ
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Old May 04, 2015, 03:31 AM
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Originally Posted by Virginia Jim View Post
I may be confused about how to tell Right Hand polarization from Left hand polarization, especially with respect to Clover Leaf, but also with respect to helical antennas, which I think are always(?) circularly polarized too, right?

I have attached a photo I took of two clover leaf antennas I purchased. These antennas were purchased from the same source together. I believe they are the same polarization. Perhaps I need help with this, but here is the method I have been told to use. If, when viewed from the top the pointed edge of the leaves point in a direction that would "cut" if rotated clockwise, then that is considered LEFT handed polarization. If, on the other hand the pointed parts of the leaf point in a direction that would "cut" if the antenna is turned in a counterclockwise direction, then that is RIGHT handed polarization. Is that right?

What is the rule for determining polarization of helical antennas?

One has 3 leaves and the other 4. Is the reason we put the 3 leaf antennas on transmitters just to decrease weight or is there another reason?

Thanks. Please be sure of your answer. I would appreciate a reference. Mine came from a Flite Test video, but as I said I may not have gotten it right.
For the polarization, this is what I find the easiest way;
When you hold the antenna straight up, so looking at it like in this photo, follow
the lobe closest to you, from the base >> up. If it goes to the right it is RHCP, if it goes to the left it's LHCP.

For the Helical it is basically the same, if it is "threaded" like a normal bolt or screw it is RH, and vice versa.


RHCP

Now for the skew vs clover; there is some controversy about what's best, Here is what the 'master' himself has to say about it:
http://www.rcgroups.com/forums/showt...2#post30857056

I followed his advice and recently made a set with two clovers and do not notice any difference with my previous SPW/CL combination
Well, actually, they are slightly better, but I also was more accurate, smaller feed gap etc
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Last edited by viper1; May 04, 2015 at 03:38 AM.
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