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Old Jan 30, 2011, 07:13 PM
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Yes, the Vtx will stand upright behind the wing of my TSII. That will place the pin-wheel about 1.5" above the wing.
At 2.4ghz, big batteries can certainly cause blind-spot.
The base station will feature an helix/pin-wheel diversity system and a 5.8ghz Vtx to "re-broadcast" into my AIO goggle that also use pin-wheels.
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Old Jan 31, 2011, 06:40 AM
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Nice work, Hugo. I can't wait to hear your results from the new system.

-Alex
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Old Feb 01, 2011, 10:43 AM
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Found out my AIO goggle and 5.8tx from Foxtech use RP-sma, if anybody want my 5.8ghz pin-wheels just PM me.

-Hugo
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Old Feb 01, 2011, 07:54 PM
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Damn, I would have bought one of your 2.4 ones from you! Sure you don't want to make another 2.4? Your antennas look like works of art.

By the way guys, Dave is doing some incredible tuning work for me on a V antenna. I will do a write up, but he has my VSWR down to 1.02 minimum and 1.04 at 2.432 mHz. Actually he is making that one from scratch.
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Old Feb 02, 2011, 07:33 AM
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Quote:
Damn, I would have bought one of your 2.4 ones from you! Sure you don't want to make another 2.4? Your antennas look like works of art.
Thx
Well, I played with the idea of making some I selling them on my website.
However, I must test them first.

-Hugo
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Old Feb 02, 2011, 08:26 PM
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Hugeone, have a look at Digikey.com for an adapter part number ACX1248-ND (CONN SMA ADAPTER JACK-R/P PLUG; Amphenol; 132171RP-10) that may solve your SMA connector issue on your AIO goggles and 5.8GHz Skew-Planar Wheel.

- Marc
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Old Feb 04, 2011, 07:19 AM
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Wow I feel really dumb....

from the first couple of pictures I was thinking that this antenna would be slightly larger than a softball, but you guys on 5.8 are making them the size of golf balls!!!!

If I made one for 1.2 would it still be about that small, or a lot bigger? -Tyler
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Old Feb 04, 2011, 08:27 AM
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Look up a few posts and you will see my esitmated measurements of my 1.3 version, and a few pics of it on my easy star.

It is relatively big, but not unweildly.
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Old Feb 04, 2011, 08:28 AM
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Ah, here it is compared to an E*

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Old Feb 04, 2011, 08:30 AM
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Or check the video. I fly a 1.3 GHz skew planar wheel. It is about 4.25" in diameter and 2" tall. About half of a softball for 1.2/1.3 GHz.

It is a bit draggy, but well worth it for the performance.

-Alex
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Old Feb 05, 2011, 12:36 PM
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Alex,

I've been reading this thread over. Question on the CP VTx antennal. Do you need a CP VRx antenna to match or will it work with a regular patch? Reason I'm asking is I see talk on the VTx side but not much in how to construct a CP VRx antenna.
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Old Feb 05, 2011, 12:42 PM
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I know you Q is aimed at Alex, but...Did you see the helical tutorial in his blog?? It is very easy Vrx antenna. Also you can use the SP antenna as RX too! I built both but weather has been very bad so I have done very little comparisons with conventional antennas.

Either way the CP can communicate with a linear antenna, you just get 3dbi automatic loss, BUT it is constant and not dependant on Vtx orientation. This is the reason it was recommended in teh past by Schrerrer (and probably others) to use a CP antenna as Vrx and linear one the plane (for convenience and since CP Vtx are rare) unless going for maximum distance, since in hard banking you do nt approach a huge dbi loss, just 3.
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Old Feb 05, 2011, 12:43 PM
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Originally Posted by Derek_S View Post
Did you see the helical tutorial? It is very easy Vrx antenna. Also you can use the SP antenna as RX too! I built both but weather has been very bad so I have done very little comparisons with conventional antennas.

Either way the CP can communicate with a linear antenna, you just get 3dbi automatic loss, BUT it is constant and not dependant on Vtx orientation. This is the reason it was recommended in teh past by Schrerrer (and probably others) to use a CP antenna as Vrx and linear one the plane (for convenience and since CP Vtx are rare) unless going for maximum distance, since in hard banking you do nt approach a huge dbi loss, just 3.
No, I'll search for that though...thanks.

Found the thread. Thanks, I'll take a read through it.
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Old Feb 05, 2011, 12:45 PM
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BTW, I did fly enough with the CP stuff to try it with CP on the plane and Linear patch on the ground, performance was ok, certainly not comprimised enough to be noticed by me, or perhaps much at all for < 1mile flying that I do.

The helical is in his blog. it is easy and cheap to construct, and looks wicked cool IMO.
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Old Feb 07, 2011, 10:55 PM
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SWR 1.3 - Not bad

I just got my new directional wattmeter up and working. I found out there is a huge HAM supply house just down the street from me! I was using a 700mW BoB TX for the measurement on a 3S Lipo. I'll let the picture say the rest.

-Alex
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Old Feb 08, 2011, 05:52 AM
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Old Feb 08, 2011, 07:12 AM
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I found the exact same thing last night. I got best results with that angle at exactly 90 degrees. Admittedly, the best VSWR I can get appears to be 1.2. But I'm happy with that. I can't sweep the whole frequency except in steps and then I'd have to graph it manually.

Let me know how much the styrofoam shifts the frequency. I have been considering a few different protection methods. Does anyone know of a cheap plastic ball that could be sliced in half to cover the 4-1/4" radius of the 1.3GHz antenna?

-Alex
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Old Feb 08, 2011, 07:30 AM
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Old Feb 08, 2011, 07:41 AM
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Hi Mictronic , what kind of tool do you use to analyse the antenna ?
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Old Feb 08, 2011, 07:50 AM
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Old Feb 08, 2011, 08:05 AM
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oh yeah 13k$
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Old Feb 08, 2011, 11:24 AM
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A word of caution about VSWR meas. Lowest SWR does not always mean the best configuration, especially when it comes to circular polarization. You can easily push the antenna from good circular polarization to primarily horizontal or vertical polarization by distorting the elements for lower SWR.

You HAVE to model the antenna to understand what is going on.

OMM
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Old Feb 08, 2011, 11:52 AM
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Old Feb 08, 2011, 01:31 PM
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A word of caution about VSWR meas. Lowest SWR does not always mean the best configuration, especially when it comes to circular polarization. You can easily push the antenna from good circular polarization to primarily horizontal or vertical polarization by distorting the elements for lower SWR.

You HAVE to model the antenna to understand what is going on.

OMM
An SWR reading really can be totally meaning less as well. I can put a 50 ohm resistor on the end of a coaxial line and get perfect SWR. We all know a resistor isn't an antenna.

Two antennas come to mind here: Yagis and helicals. Line up a set of yagi elements improperly and you can have a dummy load despite perfect SWR. Same thing with a helical. A poor shunt matched helical will have great SWR, but not resonate at all which I why I didn't cover it in the tutorial.

Still, nothing compares to a flight test (or a ground test). The skew planar wheel does wonderful on cheap RX units. Put it on a Lawmate RX and you have no signal at all. No modeling or SWR reading is going to tell you anything about a phenomenon like that.

-Alex
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Old Feb 08, 2011, 01:34 PM
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Also, note that this antenna also exhibits some opposing polarization. A RHCP skew wheel will also radiate some LHCP. Granted it's low (maybe 12 db or so), but it does do this. If you look at the way the elements look when they are flat (as a figure 8) you will see why this is.

-Alex
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Old Feb 08, 2011, 03:57 PM
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Let me be sure, if I look at the SP from the side, and the rounded part of the elements mimics a standard screw thread then it is RH polarized, correct? Just making sure as when testing my helical + sp I have not been getting good results lately, and have been looking for the problem.

Is it possible I have HAM/ATV interference in my area that is CP in nature, and thus using CP over linear will actually yeild worse results? It seems teh 1st day I tested cp at my field it worked great, the next time terrible, exact same components just different planes and different days. am not sure it is the plane setup, as I think the setup on the second day was actually better in theory (more space, more separation, filtering etc whreas the stryker had none of those)
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Old Feb 08, 2011, 09:29 PM
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Derek - I have had the same problem and am currently investigating the cause. The best way to determine polarization is to curl your fingers around any of the elements towards the center element of the coaxial cable. Thus you curl from ground to the origin so you fingers point to the origin point. What hand did you use? That's the polarization.

I'm certain the problem is in the helical. That microstrip match is fickle as can be. I just developed a more reliable match by using a tapered 1/4 wave metal strip. I will be adding it to the tutorial soon

-Alex
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Old Feb 08, 2011, 09:41 PM
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Oh, nice, I will try changing the matching device.

And it looks like both my antennas are RH, so that shouldnt be it.
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Old Feb 09, 2011, 01:33 AM
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The best way to determine polarization is to curl your fingers around any of the elements towards the center element of the coaxial cable. Thus you curl from ground to the origin so you fingers point to the origin point. What hand did you use? That's the polarization.
-Alex
Lets take for example this antenna http://www.rcgroups.com/forums/showp...3&postcount=13 If I understand this method correctly - it is right polarisation?
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Old Feb 09, 2011, 05:41 AM
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An SWR reading really can be totally meaning less as well. I can put a 50 ohm resistor on the end of a coaxial line and get perfect SWR. We all know a resistor isn't an antenna.

Two antennas come to mind here: Yagis and helicals. Line up a set of yagi elements improperly and you can have a dummy load despite perfect SWR. Same thing with a helical. A poor shunt matched helical will have great SWR, but not resonate at all which I why I didn't cover it in the tutorial.

Still, nothing compares to a flight test (or a ground test). The skew planar wheel does wonderful on cheap RX units. Put it on a Lawmate RX and you have no signal at all. No modeling or SWR reading is going to tell you anything about a phenomenon like that.

-Alex
So this design doesn't work well on the lawmate rx's? Is that correct?
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Old Feb 09, 2011, 06:26 AM
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The skew planar wheel does not work with Lawmate RECEIVERS. It works fine with the transmitter, though. I have no idea why this is. Nobody seems to know. It does awesome with every other RX.

-Alex
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Old Feb 09, 2011, 06:27 AM
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Lets take for example this antenna http://www.rcgroups.com/forums/showp...3&postcount=13 If I understand this method correctly - it is right polarisation?
Yes, that is RHCP. If you curl your fingers around the element with your right hand, they point to the centeral feed point.

-Alex
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Old Feb 09, 2011, 06:29 AM
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So, is it a requirement to ave circular polarisation on both the transmitting and recieving end? What is the disadvantages and advantages of having a CP VTx & LP VRx antenna vs LP VTx & LP VRx antenna?
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Old Feb 09, 2011, 06:40 AM
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Every system has distinct advantages and disadvantages. I will try to explain:

linear polarization on both sides - theoretically this gives the longest over all range under ideal conditions (which is seldom the case). However multipath interference and loss of polarization when banking the airplane cause loss of signal.

Linear on one side and circular on the other - Eliminates the problem with polarization loss due to banking. However there is a constant 3db drop due to polarization mis match and it will not reject multipath interference.

Circular polarization on both ends - Best choice for almost all FPV ventures. Does not lose polarization when banking and has excellent rejection of multipath interference giving the cleanest signal. Also excellent for high altitude. Theoretical range is slightly less than linear polarization, but is seldom realized.

-Alex
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Old Feb 09, 2011, 06:46 AM
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Thanks!

So, for my setup (I'm using Lawmate and Airwave VRx) I guess would be CP VTx antenna and a LP VRx antenna (such as the biQuad or a patch). I'm not going for extreme ranges but I do like to bank hard when turning.

I don't think I'll re-invest in new VRx at this time.

But is the biQuad a closed loop antenna or not, ie will it work with Lawmate VRx?
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Old Feb 09, 2011, 06:49 AM
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Alex,

Congrats on getting the Diawa. I did not realize they made one for our needs. I just bought a Bird with the proper elements on ebay. Got a couple of "N" to sma adapters and am anxious to see the actual output of my 900mhz Tx's.

Have you had a chance to evaluate the Saw filter mod on your 900mhz Rx?

If it would just warm up here maybe I could fly.......


Tom
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Old Feb 09, 2011, 01:01 PM
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Old Feb 09, 2011, 01:06 PM
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What is that ball made for? I am curious as to what kind of shop to look for it at. I looked at a craft store but didnt see anything like it.

And if the foam doesnt affect it, couldnt it also just be put inside the fuselage, provided the plane is large enough?
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Old Feb 09, 2011, 01:28 PM
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Old Feb 09, 2011, 01:40 PM
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Alex,

Congrats on getting the Diawa. I did not realize they made one for our needs. I just bought a Bird with the proper elements on ebay. Got a couple of "N" to sma adapters and am anxious to see the actual output of my 900mhz Tx's.

Have you had a chance to evaluate the Saw filter mod on your 900mhz Rx?

If it would just warm up here maybe I could fly.......


Tom
The SAW mod helped some, but not much. I got better results with a Lawmate RX on the helical antenna than I did with my modded 1.3GHz standard RXs. Unfortunately the Lawmate does not play nice with the skew-planar wheel.

900MHz TX's are VERY sensitive to having the proper antenna. The output begins to drop immediately after the SWR drops below 1.2. I just tested my first ever Vee antenna and found the SWR was about 1.3 or so which dropped the TX output to 400mW. I tested it with my new Vees and got a VSWR of 1.05 and an output of 500mW at 12VDC.

-Alex
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Old Feb 09, 2011, 02:36 PM
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Are your newer Vees more dimensionally accurate?
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Old Feb 09, 2011, 09:47 PM
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No. Every Vee I have sold is the same. I just tested my first ever Vee antenna which was made long before I started selling them. Every Vee I sold is made for SWR of 1.2 or less.

-Alex
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Old Feb 09, 2011, 11:05 PM
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Alex,

Thank you for the comments. I got both the bird and the 400-1000mhz 5 watt element today. I tested the 500mw 900mhz Vtx I had been using in my EZ. It measured, with a bird 50ohm load, 2.6 watts output. I looked at it again and that is what it read. It must be the element or the watt meter. I did buy another 1 watt 400-1000mhz element on ebay. I am off to work for a week so will test it when I get home.


Tom
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Old Feb 11, 2011, 06:18 AM
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Old Feb 11, 2011, 06:35 AM
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Nice work, Micheal! This confirms my suspicion that the antenna has some polarizaion in the opposite direction. Do you have any of the source files for 4NEC-2?

If I send you the details of my cloverleaf antenna, (which is very similar to the skew-planar wheel but with one less lobe) do you think you could model it? It is basically a 3 lobe skew-planar wheel over a ground plane .2 wavelengths away.

-Alex
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Old Feb 11, 2011, 06:35 AM
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So, I worked some math and played with Excel. A quarter of an SPW antenna will be auto calculated now. Copy, paste and rotating can be used in the 4nec2 geometric editor to complete the antenna.

OMM, what you think?

An example, calculated for 1240MHz:
Excellent. I'll give you an A+ if the element lengths and the two key angles are defined as variables inside of 4Nec2. Be sure that the one angle defining the 1/2 wavelength arc can go beyond 90 degrees. With those variables you will be able to do auto optimizations.

Can you show the RHCP vs LHCP plots in 3d Color mode?

OMM
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Old Feb 11, 2011, 06:42 AM
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Old Feb 11, 2011, 06:47 AM
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For now calculation for now is only done in Excel. Phi and Theta angle for the hot Lambda/4 element is variable.

What other plots you want to see? The above show RHCP and LHCP gain.
I would like to see the RHCP and LHCP plots in 3d like this set (from my CPOD antenna):





OMM
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Old Feb 11, 2011, 07:02 AM
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Old Feb 11, 2011, 07:05 AM
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Awesome! Excellent work Micheal! Absolutely incredible!

Do you think you could model a 3 lobe skew planar wheel over a ground plane 0.2 wavelengths away? I have been considering this as an RX antenna. It is far easier to build than a quadrafiliar helix.

-Alex
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Old Feb 11, 2011, 07:19 AM
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Old Feb 11, 2011, 07:23 AM
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Here we go:
Thanks! So comparing the two antennas:

CPOD = 1.72 dB gain with 19 dB rejection of opposite polarization

PinWheel = 0.92 dB gain with 12 dB rejection of opposite polarization

Of course the PinWheel is much lighter and easier to build than the CPOD.

OMM
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Old Feb 11, 2011, 07:59 AM
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Thanks! So comparing the two antennas:

CPOD = 1.72 dB gain with 19 dB rejection of opposite polarization

PinWheel = 0.92 dB gain with 12 dB rejection of opposite polarization

Of course the PinWheel is much lighter and easier to build than the CPOD.

OMM
Could I perhaps talk you into giving me the dimensions for your CPOD? I'd like to try it. By observation alone it appears to have 4 equal length 3/4 wave elements where each run is 1/4 wave before it's next turn. The feedpoint appears to be some sort of lowe pass filter? However I am wondering if there's a 90 degree phase shift in there somewhere or if you have capacitive/inductive linked system? Just trying to take a guess in hopes you'll give me the details. I will not post it without permission.

-Alex
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Old Feb 11, 2011, 08:26 AM
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Michael - Thanks a million! I just ran som analysis on the 3 lobe unit and now have some more thinking to do.

It appears that when the lobes are skewed the resonate as all real at 4-5% longer than their electrical wavelength. They also show a standard 120 ohm impeadance for a full wave loop. Thus the antenna resonates ate 1280 MHz, but at only 38 ohm impeadnce.

So now begs the question: Is it better to use 2 loops .1 wavelength over a ground plane? Should I orient them 180 degrees apart or 90 degrees? My thought is that this would lose circularity.

The other option is to allow the antenna to resonate with a complex impedance. My thought for this is that it would not be very efficient. Any ideas?

By the way, how did you get the circularity plots?

-Alex
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Old Feb 11, 2011, 08:41 AM
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Just fixed my Helical to a tapered strip. All this talk has me excited to try the SPW again this weekend.
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Old Feb 11, 2011, 08:54 AM
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Cloverleaf modification

Ok, now I see. I am a bit confused right now. It appears a 3 lobe wheel is more efficient and has better SWR than a 4 lobe. Circularity appears distorted. I thought it would need the ground plane to acheive proper SWR, but apparently that is not the case. The rejecting characteristics are bizzarre! Look at the horizontal plane! I based the 3 lobe design on the wheel antenna that uses a flat lobes .2 wavelengths away from ground and just bent up the sides for circularity.

Looks like I need to try this new antenna. I got an SWR of 1.2 from my skew planar wheels. Now to a 3 lobe cloverleaf, I might actually get 1.1 or better! Element length appears to be 5% longer than calculated wavelength. Compensating for 70% humidity, I'm guessing this drops to 3% or so.

So the comparisons:

Cloverleaf: 1.3 dbic forward, 9-20 db rejection, SWR = 1.2
Skew planar wheel: .92 dbic forward, 12db rejection, SWR = 1.3
CPOD: 1.72 dbic forwar, 19 dbic rejection, SWR = ?

Now the problem... How in the world am I going to make this one easy to build???

-Alex
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Old Feb 11, 2011, 08:57 AM
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Quote:
Originally Posted by Derek_S View Post
Just fixed my Helical to a tapered strip. All this talk has me excited to try the SPW again this weekend.
Try the cloverleaf as described in the above post. I can't wait to try this one. I also am building a quadrafiliar helix! FPV meets circular polarization.

Thank goodness for the work of Mictronics! My hat is off to you, sir!

-Alex
KJ4RIV
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Old Feb 11, 2011, 08:59 AM
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I think building it in 3 peices should be no problem.

I built a SPW in 4 peices. The trick was I used a small piece of PCB, and installed them on it one at a time. I made a small triangle jig out of cardboard to hold tehm at the right angle and position as I soldered. It was not bad at all really. I have no way to test it, but physically it looks good.


Dimensionally is it the same as the SPW? If so it would be a matter of minutes to take my 4 piece SPW and reconfig it to a clover leaf.
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Old Feb 11, 2011, 12:29 PM
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Quote:
Now the problem... How in the world am I going to make this one easy to build???
Look how I built mines. I simply slotted the ferrule of a coax plug with a dremel cut-off wheel to insert the four wires. If you want it at the end of a coax, just make your own ferrule with a piece of 1/8 copper tube.
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Old Feb 11, 2011, 05:20 PM
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Quote:
Originally Posted by IBCrazy View Post
... It appears a 3 lobe wheel is more efficient and has better SWR than a 4 lobe. Circularity appears distorted.

Cloverleaf: 1.3 dbic forward, 9-20 db rejection, SWR = 1.2
Skew planar wheel: .92 dbic forward, 12db rejection, SWR = 1.3
CPOD: 1.72 dbic forwar, 19 dbic rejection, SWR = ?

-Alex
First I'm glad to see the interest in doing antenna models. I would like to offer the follow suggestions:

1) Show the 3D plots. For FPV application the 2D plots are almost worthless. This is especially true when trying to compare the opposite polarity rejection.

2) Make use of variables in the 4Nec2 models so that you can more easily optimize the antenna.

3) The model will almost always show better SWR than the actual antenna where the build will have stray capacitance & inductance usually not simulated (although I have tried to incude it in some of my modeling). Getting SWR below 1.3 provides no significant improvement other than making you feel good seeing the meter reading. (The CPOD antenna model showed between 1.1 and 1.2 depending on the particular optimization)

4) Alex, I'll eventually post the CPOD model in my 3 mile omni thread along with some other models. Been a bit busy lately.

OMM
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Old Feb 11, 2011, 07:51 PM
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Weather is supposed to be good tomorrow so I hope I can test in the air. Ther Stryker is in the shop right now getting ready.
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Old Feb 12, 2011, 05:43 AM
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Old Feb 12, 2011, 12:19 PM
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Alex,

I flew with the SPW and 3 turn Helix today. IMO I got very good results. I beat a personal record and hit 2 miles with ok video. The SPW is to your specs, and the Helix got a new tapered impedance strip per your instructions.

It is not fair to comment fully but I will post the video anyways... I later found out the video wire had a loose/cold connection, so I did have video fuzziness but not likely due to the antennas. Due to this I couldnt test the cloverleaf today.

I can say that I had no apparent multipath problems (at least in comparison to previos experience with the V and a patch), It was very nice video with the regular maneuvers an easy star does. I only had a few blipps, probably temporary nulls and interference in the city. Looks like it is time ot build a higher gain Helix?

FPV 110212 EZ AP and CP Test Edited for CP (4 min 55 sec)
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Old Feb 15, 2011, 05:15 AM
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50 or 75 ohm?

OK I have got some memory wire and have started to bend.
I suddenly have to ask. If the equipment that we use is sometimes classed as CCTV and this is 75ohm.
But the other bits are 50ohm.
What cable and plugs should I be useing, 50ohm or 75ohm?
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Old Feb 17, 2011, 11:12 AM
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I built a SP out of 1mm steel music wire.
I wrapped a thin copper wire at the solder points to help with soldering. It worked.

Now I have a cloverleaf on the tx and a SP on my trimersion rx.
It works so far very well with very clean video in the house, and I can go to different rooms (walls are made with bricks and cement ) with little or no disturbances.
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Old Feb 17, 2011, 12:09 PM
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That's the exact setup I use! Same TX antenna, RX antenna and even goggles It works great. 1 mile is easy on a BoB 700mW. However somebody is doing 2 km on 10mW! I have no idea how.

-Alex
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Old Feb 17, 2011, 12:16 PM
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Quote:
Originally Posted by IBCrazy View Post
That's the exact setup I use! Same TX antenna, RX antenna and even goggles It works great. 1 mile is easy on a BoB 700mW. However somebody is doing 2 km on 10mW! I have no idea how.

-Alex
Oh, that's me doing 2km on 10mw (actually the trimersion tx is 12mw).

I have the luck of living on the mountains in south Italy (used to live in Virginia USA), and there is no wi-fi , the spectrum is pretty clean bar the cellular frequencies and umts 900-1800-1900-2100 mhz.

Where I fly from the top of the slope I can get huge range with not so great setups so my results don't really count and are not replicable near towns.
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Old Feb 20, 2011, 03:43 AM
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OK so I read the thread and have decided this is the way to go. I'm just unsure how to get those very nice symmetrical bends? Any tips? I can make a nice jig for the antenna but I'm not sure what's the best way to get those.

Quote:
Originally Posted by Derek_S View Post
I flew with the SPW and 3 turn Helix today. IMO I got very good results. I beat a personal record and hit 2 miles with ok video.
You said you were using 72Mhz?
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Old Feb 20, 2011, 06:35 AM
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IN that case I was using TLRS.
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Old Feb 20, 2011, 07:01 AM
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Originally Posted by Wizzard033 View Post
OK so I read the thread and have decided this is the way to go. I'm just unsure how to get those very nice symmetrical bends? Any tips? I can make a nice jig for the antenna but I'm not sure what's the best way to get those.



You said you were using 72Mhz?
I hand bend everything. I couldn't figure out how to make a jig for this one. I just used a measuring board. Everything else is done by hand.

-Alex
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Old Feb 20, 2011, 10:55 PM
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Cool, I have an idea to build a jig that might make this easier to build and could be adjusted and remade if necessary.
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Old Feb 22, 2011, 05:06 PM
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Originally Posted by Hugeone View Post
Found out my AIO goggle and 5.8tx from Foxtech use RP-sma, if anybody want my 5.8ghz pin-wheels just PM me.

-Hugo
They showed up in the post tonight Hugo. Merci beaucoup!

I just tried screwing them onto my RC305 and am sad to report that it looks like these SP antennas have the RP-SMA connectors, not your goggles & reciever.

I'll dig around for adapters so I can do initial ground tests and throw them on the FieldFox for antenna measurements. It may take a while before I can get to it because work is getting a bit nuts right now.

These are gorgeous pieces of tech sculpture but the axial symmetry is a bit wobbly, so I'm expecting the performance may be a bit off as well.
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Old Feb 22, 2011, 05:16 PM
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Quote:
Originally Posted by Dirt-Torpedo View Post
...I just tried screwing them onto my RC305 and am sad to report that it looks like these SP antennas have the RP-SMA connectors, not your goggles & reciever.
They are as you say, my mistake, as I say it's hectic at work and the pressure is getting to me. In either case I will get some adapters.

Thanks again.
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Old Feb 23, 2011, 01:05 PM
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Following this tutorial I built an SPW for my 5.8Ghz 200mW kit and today I've tested it on my FPV EasyStar.

I did 3 tests...but the results with SPW are not very cool:
1 - standard whip antenna on VTX and VRX
2 - SPW on VRX and whip on VTX
3 - SPW on VTX and whip on VRX

On flight 1, without SPW, I reached 1.000m with some grain after 600m and some disturbance around 900-1000m but the visual was good

On flight 2 I reached 500m with a good image, probably better than flight 1, but after 500m I got a lot of disturbance and around 800m I had to come back as there were a lot of grain and disturbance

On flight 3 I was not able to get 500m and I had to came back very soon.

I know that my SPW is probably not perfect as geometry ...but building these 5.8Ghz antennas it's not so easy.

Next days I'll try with a Cloverleaf or a Vee on VTX and the SPW on VRX and see if I can get better results.

Any suggestion?
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Old Feb 23, 2011, 01:44 PM
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If you have the extra antenna try Skew Planar wheel (SPW) -> SPW or cloveleaf (CL) -> CL or SPW -> Cl or CL -> SPW and see if that helps.
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Old Feb 23, 2011, 01:49 PM
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Quote:
Originally Posted by lucianozan View Post
Following this tutorial I built an SPW for my 5.8Ghz 200mW kit and today I've tested it on my FPV EasyStar.

I did 3 tests...but the results with SPW are not very cool:
1 - standard whip antenna on VTX and VRX
2 - SPW on VRX and whip on VTX
3 - SPW on VTX and whip on VRX

On flight 1, without SPW, I reached 1.000m with some grain after 600m and some disturbance around 900-1000m but the visual was good

On flight 2 I reached 500m with a good image, probably better than flight 1, but after 500m I got a lot of disturbance and around 800m I had to come back as there were a lot of grain and disturbance

On flight 3 I was not able to get 500m and I had to came back very soon.

I know that my SPW is probably not perfect as geometry ...but building these 5.8Ghz antennas it's not so easy.

Next days I'll try with a Cloverleaf or a Vee on VTX and the SPW on VRX and see if I can get better results.

Any suggestion?
Hello Luciano,
do you have a close-up of the solder job?
It looks like there might be a large gap between the ground and feed point.
Also your connector (ground) is touching the wires, effectively shortening those legs of the element, but without a close-up picture, it's hard to tell.


I would leave a few cm of antenna wire coming out of the connector so you can be precise with the soldering.
I had the same problem with the antenna directly soldered to the connector.
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Old Feb 23, 2011, 02:25 PM
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Having the antenna so close to surrounding metalwork of the VTx can 'block' or distort the radiation pattern from the S-P.
I made my 5.8GHz S-P at the end of a short piece of coax cable, which was recommended to me by the Canadian Radio Amateurs where I re-discovered the S-P antenna from.
They said it was better to keep the S-P at least one wavelength away from surrounding metal parts.

A S-P will always be 3db down on cross polarised antennas, that is to say, a S-P on the VTx and a whip on the VRx (or vice-versa).

The best CP performance will always be with a S-P on the VTx and either a S-P on the VRx or another CP antenna on the VRx, eg a CP helical beam.

Nigel.
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Old Feb 23, 2011, 08:10 PM
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I find the cloverleaf (3 blade) is a bit easier at 5.8GHz. It performs just as well as the skew-planar wheel in my tests. You need to compensate for the added length given from the coaxial cable sticking out of the connector by shortening the lobes a bit.

-Alex
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Old Feb 24, 2011, 12:33 AM
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Thank you for your comments and suggestions. I'll keep you informed about my next tests.
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Old Feb 24, 2011, 02:27 AM
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Quote:
Originally Posted by IBCrazy View Post
I find the cloverleaf (3 blade) is a bit easier at 5.8GHz. It performs just as well as the skew-planar wheel in my tests. You need to compensate for the added length given from the coaxial cable sticking out of the connector by shortening the lobes a bit.

-Alex
So if using a length of coax you need to reduce the length of the lobes on the 5.8G Would it also be true for 1280Mhz? If so why couldn't you use a length of coax on the 1280Mhz and the 900Mhz in order to make the antenna size a bit more manageable?
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Old Feb 24, 2011, 02:53 AM
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I always use coax in multiples of a half wavelength at the frequency in use, also allow for the velocity factor of the coax.
This way, there is less chance of the coax becoming a matching transformer and the potential for current flow on the cable itself.

Nigel.
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Old Feb 24, 2011, 12:14 PM
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Interesting TY Sir! I'll give that a try this time.

When using the coax is there an orientation to the coax that is preferable?
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Old Feb 24, 2011, 04:47 PM
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I can't do a full half-wavelength. My cables are not long enough. Would a quarter work? What is the velocity factor? Would it be better just to put it as close to the connector as possible?
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Old Feb 24, 2011, 07:11 PM
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Quote:
Originally Posted by Devonboy View Post
I always use coax in multiples of a half wavelength at the frequency in use, also allow for the velocity factor of the coax.
This way, there is less chance of the coax becoming a matching transformer and the potential for current flow on the cable itself.

Nigel.
Would you mind if I take exception to this? If the antenna is built properly and resonates at the proper 50 ohm impedance, then a 50 Ohm matching stub will result in the exact same impedance.

Remember your equation:

Zin = Z0^2/ZL

If Z0 = ZL = 50 Ohms then Zin = 50 Ohms.

Thus you can make the cable any length you want without harming the impedance match.

-Alex
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Old Feb 24, 2011, 10:57 PM
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I have some 20ga steel for picture hanging I'm going to attempt some antennae some time this weekend
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Old Feb 25, 2011, 02:06 AM
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Quote:
Originally Posted by IBCrazy View Post
Would you mind if I take exception to this? If the antenna is built properly and resonates at the proper 50 ohm impedance, then a 50 Ohm matching stub will result in the exact same impedance.

Remember your equation:

Zin = Z0^2/ZL

If Z0 = ZL = 50 Ohms then Zin = 50 Ohms.

Thus you can make the cable any length you want without harming the impedance match.

-Alex
I'm not disagreeing Alex, and that is good theory in an ideal situation.
In the real world, all things are not equal and less than perfect.

It is so easy to calculate and use a length of coax in a multiple of half wavelength, why not just do it?

Nigel.
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Old Feb 26, 2011, 03:00 PM
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Quote:
Originally Posted by IBCrazy View Post
I find the cloverleaf (3 blade) is a bit easier at 5.8GHz. It performs just as well as the skew-planar wheel in my tests. You need to compensate for the added length given from the coaxial cable sticking out of the connector by shortening the lobes a bit.
-Alex
Following MarcAntonio, Alex, Devonboy and Mikey-flies suggestions I've modified the Skew Planar. Cutted the 4 lobes that now are 2mm shorter and soldered on the connector side. I have reduced the coax cable that was sticking out and now the coax is soldered to the antenna as soon as it exits from the connector. The geometry is not Star Trek and can be improved in the next prototypes.

I've also built a Cloverleaf for the VTX ...and it's really easier to do. Following Devonboy suggestion I've kept the antenna a little far from the VTX, soldering it on top of a little coax cable (half wavelength long).

Today I've done the same flight tests on the same course and the results are pretty good! I've got my target 1000m (0,62 mile) with video much more clean and with less disturbance even when the model was banking.

Here a little video. The first part of the video is done with the whip standard antenna. In the second part the same course is done with the new IBCrazy antennas. I think that the difference is evident. I've left all the sounds (forgot to switch off the vario) so you can better appreciate the disturbance....or the silence!

Thank you Alex for your tutorial and thank you all for your support!

Luciano

http://www.youtube.com/watch?v=-_wXTwjepsk
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Old Feb 26, 2011, 06:43 PM
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Awesome antenna! Well done! Both of them look incredible. Now you need to try a helical!
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Old Feb 27, 2011, 12:21 AM
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@IBCrazy or anyone with the knowledge

Will 20ga steel picture hanging wire be good?
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Old Feb 27, 2011, 02:22 AM
O <- this a ground loop
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Quote:
Originally Posted by Wizzard033 View Post
@IBCrazy or anyone with the knowledge

Will 20ga steel picture hanging wire be good?
It won't solder well but in terms of thickness it should be fine.

Thickness is best judged by being thin enough to bend in making but thick enough to not deform at speed due to oncoming air flow.

Ren
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Old Feb 27, 2011, 02:25 AM
O <- this a ground loop
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Quote:
Originally Posted by lucianozan View Post
Following MarcAntonio, Alex, Devonboy and Mikey-flies suggestions I've modified the Skew Planar. Cutted the 4 lobes that now are 2mm shorter and soldered on the connector side. I have reduced the coax cable that was sticking out and now the coax is soldered to the antenna as soon as it exits from the connector. The geometry is not Star Trek and can be improved in the next prototypes.

I've also built a Cloverleaf for the VTX ...and it's really easier to do. Following Devonboy suggestion I've kept the antenna a little far from the VTX, soldering it on top of a little coax cable (half wavelength long).

Today I've done the same flight tests on the same course and the results are pretty good! I've got my target 1000m (0,62 mile) with video much more clean and with less disturbance even when the model was banking.

Here a little video. The first part of the video is done with the whip standard antenna. In the second part the same course is done with the new IBCrazy antennas. I think that the difference is evident. I've left all the sounds (forgot to switch off the vario) so you can better appreciate the disturbance....or the silence!

Thank you Alex for your tutorial and thank you all for your support!

Luciano

http://www.youtube.com/watch?v=-_wXTwjepsk
Luciano,

bit worried about your VTX placement right next to your GPS.

If you fly any kind of distance and have need for accurate GPS (plane down locating or RTH etc) then you would be best to seperate them out of principle even if the frequencies and harmonics are not a real factor.
Call it best practices if you will.

Ren
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Old Feb 27, 2011, 02:58 AM
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Italy
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Quote:
Originally Posted by devfor View Post
...bit worried about your VTX placement right next to your GPS.

If you fly any kind of distance and have need for accurate GPS (plane down locating or RTH etc) then you would be best to seperate them out of principle even if the frequencies and harmonics are not a real factor.
Call it best practices if you will.

Ren
Hi Ren!

Thanks...you are right! I was worried too about the GPS placement ...and in the first time (with 2.4Ghz kit) I put it far from VTX. Now with this 5.8Ghz kit I've built an FPV pod that I can move among models so I need to keep everything pretty close...well... at 5.8Ghz the VTX seems to have little effect on GPS. It finds satellites very soon (10-11 sat during flight) and the info on OSD look to me quite accurate (compared with other barometric telemetry sensor).

BTW on my MaxiSWIFT with 5.8Ghz kit I've put the GPS very very far from VTX....best practices...you never know...

Luciano
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Old Feb 27, 2011, 03:03 AM
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First, my apology if this has been asked before, but could I benefit from using the skew planar or the cloverleaf on my Spektrum transmitter?
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Old Feb 27, 2011, 03:09 AM
Happy FPV pilot
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Italy
Joined Feb 2009
148 Posts
Quote:
Originally Posted by IBCrazy View Post
Awesome antenna! Well done! Both of them look incredible. Now you need to try a helical!
Thank you Alex! I understand that helical are pretty directive and as I normally fly 360 around me looking for thermals I believe that a non directive antenna should be better....is it correct?

Next tests will be a new Cloverleaf mounted at 90 under the FPV T-REX450 boom. With the standard whip in the same position I get a lot of disturbance when the heli is flying low facing the ground station ...if I land a bit far sometimes I even loose the video signal. I'll let you know!!!

Luciano
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Old Feb 27, 2011, 05:59 AM
Happy FPV pilot
lucianozan's Avatar
Italy
Joined Feb 2009
148 Posts
Quote:
Originally Posted by lucianozan View Post
Next tests will be a new Cloverleaf mounted at 90 under the FPV T-REX450 boom. With the standard whip in the same position I get a lot of disturbance when the heli is flying low facing the ground station ...if I land a bit far sometimes I even loose the video signal.
Tested today the magic Cloverleaf on my T-REX450 FPV.

It's great! I've no video but, believe me, it works really well! very few disturbance during flight in all directions and even when the heli is flying low, nose in, the video signal is good. Tried landing far from the ground station and with the heli on the ground I had still a good image and I was able to take off without any problem.

...now I'm building CP antenna for all my models!!

Luciano
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Old Feb 27, 2011, 08:20 AM
HeliAP'er!
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Surrey, UK
Joined Aug 2003
8,204 Posts
Subscribing It looks like this antenna would work very well on my aerial photography setup. At the moment I'm using a 3dBi whip antenna on the VTx (Airwave 661 5.8GHz 25mW), and an 8dBi linear-polarised patch antenna on the VRx (Airwave 682 5.8GHz).

At the moment I'm getting quite a lot of (what I've been told might be) multi-path interference that's causing my LCD monitor to go blank temporarily. This is the raw video which I was able to capture:

Airwave 5.8GHz video link test (3 min 18 sec)


I need to do another test with everything in exactly the same position, but I don't think the LCD would have coped very well with that interference

Unlike FPV, my main use for this platform is hovering 50-100m from a subject that is being photographed ... I assumed that LP antennas wouldn't cause too many problems, but I gather that LP antennas are more susceptible to multi-path interference than CP antennas, hence my interest in this thread!

Thanks for all the incredible info that's being shared here!


David
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Old Feb 27, 2011, 09:48 AM
HeliAP'er!
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Surrey, UK
Joined Aug 2003
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Quote:
Originally Posted by IBCrazy View Post
I find the cloverleaf (3 blade) is a bit easier at 5.8GHz. It performs just as well as the skew-planar wheel in my tests. You need to compensate for the added length given from the coaxial cable sticking out of the connector by shortening the lobes a bit.

-Alex
Hi Alex

Can you elaborate on how much shorter the lobes need to be? If the cloverleaf performs just as well as the SPW, I'll probably try building one of those ... 3/4 of the parts to make accurately!

Many thanks for all your support / help in this thread!


David
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Old Feb 28, 2011, 07:15 AM
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Joined May 2010
237 Posts
Hello,
just made a SP antenna. Does that look right?


and I have a question:
I have FatShark 100mW 2.4GHz transmitter witch has a wire instead of antenna. Can I just solder the coaxial with SP instead of that wire?


Thanks
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Old Feb 28, 2011, 09:18 AM
O <- this a ground loop
Japan
Joined Nov 2010
514 Posts
Quote:
Originally Posted by aSa2 View Post
Hello,
just made a SP antenna. Does that look right?


and I have a question:
I have FatShark 100mW 2.4GHz transmitter witch has a wire instead of antenna. Can I just solder the coaxial with SP instead of that wire?


Thanks
asa2,

it looks like you know what you are doing.

Just be careful that you use a hot iron and don't push down on the tracks around the RF module too hard.
They can be a bit fragile.

And remember to visually inspect for shorts before you power it up.

good luck

Ren
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