Espritmodel.com Telemetry Radio
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Old May 27, 2011, 11:06 PM
QiW
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south east asia
Joined Mar 2009
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i will try both this weekend and let u guys know
there is also a telco GSM 900/1800 200m from where i stand .. hehehehe
tested on car roof and on asphalt ground this morning ..
overall height from ground using tripod alone was 5ft
overall height on the roof of the car was around 7.5ft (i shortened the tripod legs when on the roof)

at higher altitudes ... the ground and roof version performed about the same
but at lower heights the roof version seemed better marginally .. lower = 10-20ft weaving around small trees and lamp posts (in a cloudsfly .. hehehe)

i also noticed when i/plane fly over greens/grass/trees ... signal is much better than when over roads .. high metal content in the asphalt/tar road construction in my country ??
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Old May 28, 2011, 12:22 PM
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AleG's Avatar
Bangkok
Joined Oct 2007
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Alright, I'm going to build one this weekend to use with a 5.8Ghz transmitter.

I just tested and it turns out that it's actually very easy to solder an electric guitar steel wire, so I'm going to use that for the antenna.

One thing I'm not quite sure though. For the receiver end, should I make an identical antenna or is it better to use a different model?
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Old May 28, 2011, 12:29 PM
Oh so close!
clipper99's Avatar
Campbell River
Joined Jan 2010
702 Posts
The recommended antenna for the TX is the circular polarized antenna and the SPW is for the RX.

http://www.rcgroups.com/forums/showthread.php?t=1388264

Have fun!
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Old May 28, 2011, 01:49 PM
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Bangkok
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Originally Posted by clipper99 View Post
The recommended antenna for the TX is the circular polarized antenna and the SPW is for the RX.

http://www.rcgroups.com/forums/showthread.php?t=1388264

Have fun!
Ah yes. I'm reading up on that.

Another question, I'm planning to mount the SPW Tx antenna upside down in the fuselage in a small bulge under the nose, which if I'm not mistaken would switch the polarization. So, should I make a left hand SPW and a right hand Cloverleaf so they match?
Or is that an entirely bad idea and I should mount it with the curved segments pointing up?

I attached a drawing of how I'd like to install the antenna (in red), the big rectangle on top is the battery, and smaller one the Vx transmitter.
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Old May 28, 2011, 01:54 PM
Kiwi in Germany
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Germany
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Originally Posted by AleG View Post
Ah yes. I'm reading up on that.

Another question, I'm planning to mount the SPW Tx antenna upside down in the fuselage in a small bulge under the nose, which if I'm not mistaken would switch the polarization. So, should I make a left hand SPW and a right hand Cloverleaf so they match?
Or is that an entirely bad idea and I should mount it with the curved segments pointing up?

I attached a drawing of how I'd like to install the antenna (in red), the big rectangle on top is the battery, and smaller one the Vx transmitter.
It does NOT switch the polarization. right hand is always right hand even if it is upside down.
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Old May 28, 2011, 05:00 PM
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Schweiz, BE, Neuenegg
Joined Apr 2011
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quick question:
what happens to the directivity of an cloverleaf or a skew planar wheel if i change the numbers of lobes i.e. 2,5,6,7,8 or more lobes?
and witch one should i use on the tx and witch one on the rx?
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Old May 29, 2011, 01:45 AM
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Bangkok
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Argh!, I just realized I used the wrong dimensions for the wire length, I used a 105mm long wire to make an antenna for 5.945Ghz and according to the formula it should had been 101.1mm long.

Anyway, I did bend on element with that wire (let's call it a practice round) and found out that the ends of the wire didn't meet at the center, which had me puzzled until I looked back at the first post and noticed that the bend is actually not a circle.
I bent a circle with a diameter equal to the straight center section, and things didn't add up.

I made a drawing of how I bent the wire so you see how the arc segment I ended up with is 24.8mm instead of 26.4 (this is the wrong dimensions, haven't corrected them yet) So what I figured is that the curve is not a circle, what I haven't figured out is what shape it is supposed to be, an ellipse perhaps? I don't know how important is to get the correct curvature.

Anyway, back to bending wire....
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Old May 29, 2011, 03:52 AM
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Alberta, Canada
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It is hard to tell from the pictures but it looks like the arcs in most of the antenna do not start tangentially to a circle but rather start with a wider than 90 deg angle which may help to explain the discrepancy as this pushes the lobe outward some increasing the length of wire. Whether or not this *should* be the case or not I can't say.
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Old May 29, 2011, 04:03 AM
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Bangkok
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Originally Posted by Mikey-flies View Post
It is hard to tell from the pictures but it looks like the arcs in most of the antenna do not start tangentially to a circle but rather start with a wider than 90 deg angle which may help to explain the discrepancy as this pushes the lobe outward some increasing the length of wire. Whether or not this *should* be the case or not I can't say.
I did a new set of drawings and this time I used the correct dimensions, on the finished shape I used the correct length for the curve (25.3mm), you can see how it compares with a perfect circle segment (in blue).
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Old May 29, 2011, 06:14 AM
Kiwi in Germany
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Germany
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I did a new set of drawings and this time I used the correct dimensions, on the finished shape I used the correct length for the curve (25.3mm), you can see how it compares with a perfect circle segment (in blue).

Nice. adding this to my FPV folder for later use. Have you tested your antennas to see that they work well on channel 8

How did you go about working out the correct curve. My math has gone down hill over the years and ... I am not that smart anymore.
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Old May 29, 2011, 09:39 AM
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Nice. adding this to my FPV folder for later use. Have you tested your antennas to see that they work well on channel 8

How did you go about working out the correct curve. My math has gone down hill over the years and ... I am not that smart anymore.
I did the drawing in CorelDraw, I have an utility that tells me the length of a line, so I modified a circle arc sector until it had the precise length; the shape goes by the looks-about-right formula.
I haven't tested the antennas yet because I haven't even finished them, I just put the bent wires aside and I'll wait for a new video Tx to test them on, I don't want to tear apart my FPV plane to try them just yet.

I did check the math to calculate the length of an ellipse arc sector but it required more brain power that I can muster on a Sunday afternoon.
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Old May 29, 2011, 12:40 PM
Kiwi in Germany
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Originally Posted by AleG View Post
I did the drawing in CorelDraw, I have an utility that tells me the length of a line, so I modified a circle arc sector until it had the precise length; the shape goes by the looks-about-right formula.
I haven't tested the antennas yet because I haven't even finished them, I just put the bent wires aside and I'll wait for a new video Tx to test them on, I don't want to tear apart my FPV plane to try them just yet.

I did check the math to calculate the length of an ellipse arc sector but it required more brain power that I can muster on a Sunday afternoon.
My current antennas are made for the 5705 band. Since I am pushing the distance I can really feel that they are not near channel 8. I am thinking of making some at for that channel.
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Old May 29, 2011, 02:56 PM
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United States, FL, Plantation
Joined Nov 2005
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hey guys... tell me if these look ok.

So far, they seem to have worked a bit better than the dipoles. 5.8ghz 200w foxtech system.

Not sure if its good or not, but with the dipoles i was able to get about 300 feet. Now I can get 500 feet.

I attached a map to show my environment.

The camera/TX is mounted on a 1/10th scale car. So I am hoping once the TX is on a plane, I will get out a bit farther. Am I correct to think range will increase in the air?
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Old May 29, 2011, 02:57 PM
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FYI, the black stuff is heat shrink tube and liquid electrical tape.
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Old May 29, 2011, 03:37 PM
Kiwi in Germany
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Germany
Joined Jun 2010
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Originally Posted by GregSilver View Post
hey guys... tell me if these look ok.

So far, they seem to have worked a bit better than the dipoles. 5.8ghz 200w foxtech system.

Not sure if its good or not, but with the dipoles i was able to get about 300 feet. Now I can get 500 feet.

I attached a map to show my environment.

The camera/TX is mounted on a 1/10th scale car. So I am hoping once the TX is on a plane, I will get out a bit farther. Am I correct to think range will increase in the air?
I use these on my 5.8ghz 200mw system and easily get 1km with a clear picture. I have flown them out to 3km (9000 feet). If you can build these you can also build yourself a 4 turn helical for extra range.
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